Symposium Organizers
Venkatraman Gopalan The Pennsylvania State University
Jon-Paul Maria North Carolina State University
Manfred Fiebig Max-Born-Institut
Ce-Wen Nan Tsinghua University
T1: Multiferroics: Past, Present, and Future Perspectives
Session Chairs
Manfred Fiebig
Venkatraman Gopalan
Monday PM, November 27, 2006
Room 302 (Hynes)
9:30 AM - **T1.1
Historical Milestones on the Route to Maximal Single Phase Multiferroic Complexity.
Hans Schmid 1
1 , University of Geneva, Geneva Switzerland
Show AbstractSome milestones since the nineteen fifties, having lead to the present day level of understanding of complex single phase multiferroics, will be highlighted, partly based on experience gained with the crystal family of boracites M3B7O13X, where M stands for a bivalent 3d-transition metal ion and X for an ion of the halogens F, Cl, Br or I1.Multiferroics have originally been defined as materials with two or more so-called primary ferroic properties - ferro(i)magnetism, ferroelectricity, ferroelasticity - occurring in a single phase1. In recent times ferrotoroidicity, characterized by a spontaneous toroidal moment, was recognized to complete this family of analogues2.The presence of two or more ferroic properties in a single phase is ruled by stringent symmetry and structural requirements. The occurrence of a spontaneous polarization, magnetization and toroidization (toroidal moment)2 in a common phase is restricted to 9 Heesch-Shubnikov point groups, out of a total of 122. Additional ferroelasticity with centro- or noncentrosymmetry of the prototype phase plays a key role for partial or full coupling between named primary ferroic spontaneous quantities and the associated coupled or non-coupled domain switching, respectively3. However, ferroelasticity can sometimes act as a troublemaker.When considering induced toroidal moments, several novel secondary ferroic phenomena can be postulated, such as electrotoroidic, magnetotoroidic, piezotoroidic effects, toroidal optical SHG and toroidal optical rectification2. No experimental evidence for these effects has been reported so far.Measurements of the linear magnetoelectric effect with strong asymmetry of the off-diagonal tensor components have brought evidence in several substances for the presence of a spontaneous or spin-flop-induced toroidal moment4. The recent first monitoring of ferrotoroidic domains5 has brought further, compelling support for this novel type of primary ferroic. Multiferroic complexity increases with the highest allowed number of ferroic domains of an Aizu-species (prototype/ferroic phase point group pair). This number increases with increasing number of types of ferroic order in a single phase and with decreasing symmetry of that phase. Thus a triclinic triple-ferroic-phase perovskite would reach a maximum of 96 domain states in principle. In case of the additional presence of ferrotoroidic domains5,6 that number would be doubled in principle. As a consequence, applications of coupled switching appear feasible only, if Aizu species with a small number of domain states are used. 1. H. Schmid, Ferroelectrics, 162, 317-338(1994); 2. H. Schmid, Ferroelectrics, 252, 41(2001); 3. H. Schmid, Ferroelectrics, 221, 9-17(1999);; 4. Ref. in: H. Schmid in: M. Fiebig et al(eds.), Magnetoelectric Interaction Phenomena in Crystals, 1-34(2004), Kluwer Academic Pub. 5. Bas B. van Aken, M. Fiebig, J.-P. Rivera and H. Schmid, Symposium T; 6. D.G. Sannikov, Ferroelectrics, 291, 157(2003).
10:00 AM - **T1.2
Progress in Thin Film Magnetoelectric Multiferroics.
Nicola Spaldin 1
1 Materials Department, University of California, Santa Barbara, California, United States
Show Abstract10:30 AM - **T1.3
Ferroelectricity from Electron Ordering.
Naoahi Ikeda 1 , Shigeo Mori 2 , Kenji Yoshii 3
1 Physics, Okayama University, Okayama, Okayama pref., Japan, 2 1Department of Physical Science, Osaka Prefecture University, Sakai, Osaka, Japan, 3 Synchrotron Radiation Research Center, Japan Atomic Energy Research Institute , Sayo, Hyogo, Japan
Show Abstract We report a mixed valence oxide RFe2O4 become a ferroelectric originated from the polar electron ordering and free from the ionic displacement. We confirmed Fe3+ and Fe2+ order with a resonant X-ray scattering. The proved ion arrangement possesses an electric polarization. The arrangement of Fe3+ and Fe2+ is explained by the competing interaction between Fe3+ and Fe2+ in triangular lattice. The ferroelectricity arise from the electron distribution shows a direct coupling of degrees of freedom among charge, spin and orbital. RFe2O4 (R=Y or Dy to Lu) is a layered triangular lattice oxide with the spacegroup r-3m(166). The structure is expressed as an alternating stacking of triangular layers composed of rare earth, oxygen and iron ions. The iron triangular plane contains an equal amount of Fe2+ and Fe3+. Comparing to the average valence of Fe2.5+, the Fe2+ and Fe3+ act as an excess half electron (negative charge) and a deficient half electron (positive charge), respectively. Thus the coexistence of Fe2+ and Fe3+ in triangular plane brings a charge frustration on the arrangement for both ions. Taking the competing charge interactions between Fe2+ and Fe3+ into the account the ordering model for Fe2+ and Fe3+ was derived. The model holds an electric polarization since the weight center of Fe2+ and Fe3+ do not coincide. In order to give a proof for the charge ordering we measured the intensity of the superlattice diffraction signal (1/3 1/3 5.5) in the function of X-ray energy near the Fe-K absorption edge. The characteristic enhancements, a maximum at 7.11keV and a minimum at 7.12 keV, show that the difference of the atomic scattering factor for Fe3+ and Fe2+ forms the structure factor of this superlattice. This is the proof for the formation of the superstructure by the ordering from Fe2+ and Fe3+. The index of the super reflection spot indicates that the super cell of Fe2+ and Fe3+ is three times larger than the chemical unit cell within a-b plane. This result gives the same conclusion with the charge ordering model. The presence of the electric polarization by the iron charge ordering gives the consistent explanation for the dielectric response of RFe2O4. For example, LuFe2O4 shows giant dielectric constant up to 5000 with weak temperature dependences below the room temperature. The dielectric relaxation frequency coincides with the iron valence fluctuation frequency, which shows that the polarization switching proceeds with the electron hopping on the iron ions. The electron fluctuation frequency coincides with the characteristic frequency of dielectric response. The electric polarization derived from the pyroelectric current measurement appears below 350K where the charge superstructure develops. This fact indicates that the charge ordering is the order parameter of the electric polarization.reference: N. Ikeda, et al., Nature 436, 1136 (2005).
11:30 AM - **T1.4
Multiferroicity and Colossal Magneto-capacitive Coupling in Transition-metal Compounds.
Joachim Hemberger 1 , Florian Schrettle 1 , Peter Lunkenheimer 1 , Andrei Pimenov 1 , Alexander A. Mukhin 1 2 , Anatoli M. Balbashov 3 , Vladimir Tsurkan 1 4 , Alois Loidl 1
1 Center for Electronic Correlation and Magnetism, University of Augsburg, 86135 Augsburg Germany, 2 , General Physics Institute of the Russian Academy of Sciences, 119991 Moscow Russian Federation, 3 , Moscow Power Engineering Institute, 111250 Moscow Russian Federation, 4 Institute of Applied Physics, Acadeny of Sciences of Moldova, 2028 Chisinau Moldova (the Republic of)
Show AbstractIn recent years multiferroic magnetoelectrics attracted an increasing scientific and technological interest. In this rare class of compounds ferroelectricity (or at least a weak ferroelectric component) and (ferro-)magnetism coexist and both order-parameters are strongly coupled. Prominent examples for such type of materials are the heavy rare earth manganites like TbMnO3, where the partial frustration in the spin-sector leads to spiral magnetic structures inducing finite ferroelectric polarization [1]. The system (Eu:Y)MnO3 [2] offers the possibility to continuously control the orthorhombic distortion of the orbitally ordered perovskite structure and thus to tune the corresponding multiferroic phases without the additional influence of a magnetic rare earth moment. A second example shall be the normal cubic spinels ACr2S4 (A = Cd, Hg, Zn) which in contrast to the manganites do not posses a Jahn-Teller active orbital degree of freedom. CdCr2S4 is a ferromagnetic semiconductor (Tc = 84 K) exhibiting pronounced magneto-resistive and magneto-capacitive effects near the magnetic transition [3]. In this system the dynamics of the dielectric relaxation is strongly influenced by the onset of magnetization.
Besides a detailed characterization of magnetic properties, specific heat, and electric polarization, the discussed materials have been studied using magnetic field dependent broadband dielectric and optical spectroscopy.
[1] T. Kimura et al., Nature 426, 55 (2003)
[2] K. Noda et al., J. Appl. Phys. 99, 08S905 (2006)
[3] J. Hemberger et al., Nature 434, 364 (2005)
This work was partly supported by the Bundesministerium für Bildung und Forschung via grant No. VDI/EKM 13N6917-A and by the Deutsche Forschungsgemeinschaft (SFB 484).
12:00 PM - **T1.5
New Magnetic Twists for Ferroelectricity
Sang-Wook Cheong 1
1 Department of Physics & Astronomy, Rutgers University, Piscataway, New Jersey, United States
Show AbstractExtraordinary cross-coupling effects between magnetism and dielectric properties in multiferroics where magnetic and ferroelectric orders coexist have been observed recently. For example, the highly reproducible electric polarization reversal in TbMn2O5 and TbMnO3 and unprecedented large change of dielectric constant in DyMn2O5 and DyMnO3 can be activated by an applied magnetic field (H). Furthermore, acoustic phonons in hexagonal–HoMnO3 can be significantly influenced by H. It turns out that the ferroelectricity in those multiferroics arises from non-colinear magnetic orders with inversion symmetry broken, originating from magnetic frustration. Examples of the non-colinear magnetic orders include spiral magnetic orders.
12:30 PM - **T1.6
Ferroelectricity Induced by Magnetic Order.
Tsuyoshi Kimura 1
1 , Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey, United States
Show AbstractT2: Ferroic Thin Films
Session Chairs
Monday PM, November 27, 2006
Room 302 (Hynes)
2:30 PM - T2.1
Enhanced Dielectric Properties in Ferroelectric Barium Titanate Thin Films.
Jon Ihlefeld 1 3 , Bill Borland 2 , Jon-Paul Maria 1
1 Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States, 3 Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania, United States, 2 , Dupont Electronic Technologies, Research Triangle Park, North Carolina, United States
Show Abstract2:45 PM - T2.2
First-Principles Study of Domain Evolution in Ferroelectric Ultrathin Films.
Bo-Kuai Lai 1 , Inna Ponomareva 1 , Ivan Naumov 1 , Igor Kornev 1 , Huaxiang Fu 1 , Laurent Bellaiche 1 , Greg Salamo 1
1 Physics, U of Arkansas, Fayetteville, Arkansas, United States
Show AbstractOver the past decade, ferroelectric thin films have attracted considerable research interest because of their applications in computer memories and radio frequency and microwave devices. With the miniaturization and performance-enhancement trend of the devices, our fundamental understanding on nanoscale ferroelectric thin films is extremely critical to push forward the existing technology and explore new possibilities of ferroelectric applications. The aim of this work is to use first-principles method to reveal and provide unprecedented detailed atomistic features (which are rather challenging to extract from measurements) of the evolution of recently discovered periodic 180o stripe domains in ferroelectric ultrathin films [Phys. Rev. Lett. 89, 067601 (2002)] under external electric fields. Here, we investigate Pb(Zr0.5Ti0.5)O3 (PZT) films that are grown along the [001] direction (which is chosen to be the z-axis) and assumed to be Pb-O-terminated at all surfaces. They are modeled by 40×24×m supercells that are periodic along the x- and y-axes (which are chosen along the [100] and [010] pseudo-cubic directions, respectively), where m is the number of finite (001) B-layers along the non-periodic z-axis. We use the total energy provided by an effective Hamiltonian into Monte-Carlo simulations. Mechanical and electrical boundary conditions are chosen to be close to realistic thin films: the misfit (compressive) strain is –2.65% and the screening corresponds to 81% of the maximum depolarizing field. The external electric field (Ez) is applied along the z-axis. Without the external electric field, the PZT ultrathin films having a thickness of 20 Å form periodic stripe domains with periodicity of 8 unit cells (32 Å). Each period consists of two stripe domains with (mostly) opposite out-of-plane dipoles alternating along the x-axis. As the electric field increases, the domain evolution is rather unusual and involves: (1) the lateral growth of majority dipole domains at the expense of minority domains with the overall stripe periodicity remaining unchanged; (2) the creation of surface-avoiding nanobubbles via the “breaking” of minority stripe domains; and (3) the formation of a single monodomain state. We will also discuss its analogies/differences with (i) ferroelectric thin films made of BaTiO3 and (ii) ferromagnetic thin films under magnetic field. In summary, the domain evolution of epitaxial ferroelectric ultrathin films under an applied electric field and the corresponding atomistic insight have been revealed using first-principles. [Phys. Rev. Lett. 96, 137602 (2006)] We hope that our predictions, and in particular the formation of nanobubbles, will be confirmed soon and will lead to further investigations on the fascinating topic of domain structures in low-dimensional ferroelectrics.
3:00 PM - **T2.3
Phase-field Approach to Predicting Domain Structures in Nanoferroics
Y. Li 1 2 , S. Choudhury 1 , J. Zhang 1 , A. Soukiassian 3 , J. Haeni 1 , A. Vasudevarao 1 , D. Tenne 3 , F. Zavaliche 4 , E. Chu 4 , K. Choi 5 , Q. Jia 2 , C. Eom 5 , R. Ramesh 4 , X. Xi 3 1 , V. Gopalan 1 , D. Schlom 1 , Long-Qing Chen 1
1 Materials Science and Engineering, Penn State University, University Park, Pennsylvania, United States, 2 Division of Material Science Technology, Los Alamos National Lab, Los Alamos, New Mexico, United States, 3 Physics, Penn State University, University Park, Pennsylvania, United States, 4 Materials Science and Engineering, UC Berkeley, Berkeley, California, United States, 5 Materials Science and Engineering, University of Wisconsin, Madison, Wisconsin, United States
Show AbstractThis talk will briefly review our recent work on theoretical predictions of domain structures and switching in nanoferroics using the phase-field approach. Examples to be discussed include ferroelectric and multiferroic thin films such as BaTiO3, PbTix Ti1-xO3, BiFeO3, SrTiO3, BaTiO3/CoFe2O4 nanocomposites and BaTiO3/SrTiO3 superlattices. In this approach, a nanoscale domain structure is described using a set of spatially inhomogeneous distributions of order parameters such as polarization, magnetization, antiferrodistortion, and strains. Their temporal evolution and relaxation toward are obtained by solving the coupled time-dependent Ginzburg-Landau equations and/or Landau-Lifshitz Gilbert equations as well as the electrostatic, magnetostatic, and mechanical equilibrium equations. For a given set of electrical, magnetic and mechanical boundary conditions, it has the advantage of not only predicting phase transition temperatures but also domain structures without a priori assumptions on the domain states and domain wall orientations. In particular, the roles of strain, film orientation and electrical boundary conditions in the domain structures and domain switching will be discussed. The predicted transition temperatures and domain structures show excellent agreement with available experimental measurements and observations in the same systems.
3:30 PM - T2:ThnFilm
Break
4:30 PM - T2.4
Enhanced Dielectric and Pyroelectric Response from Epitaxial Ferroelectric Films on Anisotropic Substrates.
Gursel Akcay 1 , Ibrahim Misirlioglu 1 , Pamir Alpay 1
1 Materials Science and Engineering, University of Connecticut, Storrs, Connecticut, United States
Show AbstractWe develop a thermodynamic model to determine the polarization, dielectric permittivity, tunability and pyroelectricity of epitaxial ferroelectric films grown on orthorhombic substrates. Orthorhombic substrates induce anisotropic in-plane stresses in the film that can be described using two distinct misfit strains. In particular, we study the film thickness dependence of the dielectric tunability and the pyroresponse in epitaxial Ba0.6Sr0.4TiO3 and BaTiO3 films on NdGaO3 substrates in accordance with the experimentally established epitaxial relation (110)Film//(001)Substrate. The analysis takes into account the thickness dependence of the internal stress state due to the anisotropic relaxation of epitaxial stresses through the formation of misfit dislocations along the two in-plane directions. We predict significant improvement in the pyroelectricity and tunability of both films with increasing film thickness compared to the similar films grown on cubic substrates.
4:45 PM - T2.5
Topotactic Anion Exchange – A New Route to Epitaxial Oxides.
Mark Zurbuchen 1 , Darrell Schlom 2
1 Microelectronics Technology Department , The Aerospace Corporation, El Segundo, California, United States, 2 Department of Materials Science and Engineering, The Pennsylvania State University, Oak Ridge, Tennessee, United States
Show AbstractThe standard approach to depositing epitaxial oxide films is to deliver metal atoms and oxygen simultaneously to a substrate surface. This leads to the problematic constraint that a substrate must be stable under the oxidizing conditions of deposition, making it very difficult to grow epitaxial oxides on certain substrates. Direct growth, however, is not the only option. Topotactic anion exchange offers an alternative route.There exist certain material systems which share a common cation substructure across a wide range of chemistries, which also exhibit wide ranges of solid solubility with one another. But, a crystal of one pure composition, for example a nitride, cannot in principle be transformed to an oxide through a purely diffusive anion exchange reaction, because the large change in lattice parameter from one phase to the other leads to excessive lattice strain, and therefore to mosaic texture and cracking of a film or crystal. However, wide solid solubility between several structurally similar systems enables tuning of the lattice parameter via anion alloying. Thus, one can synthesize a nonoxide material having the same lattice parameter, and having the same cation substructure, as a corresponding oxide material. This enables a topotactic anion exchange – the product crystal inherits its orientation and texture from the precursor crystal – because the change in lattice parameter between precursor and product is zero. No long-range lattice strain develops upon anion exchange.Applications of this new synthesis route are extensive. The approach could enable straightforward growth of epitaxial oxides and epitaxial oxide template layers on oxidation-sensitive substrate materials, such as Si, GaAs, GaN, Cu, Ni, and many others. Oxide template layers grown by this method can also retain strong texture despite misfit between substrate and oxide film. The approach can also lead to increased control of strain in films, by tailoring precursor anion chemistry to control the relative change in lattice parameter between precursor and product. Stronger orientation control than is currently achievable is also possible on some substrates. Synthesis of metastable phases is enabled via the approach. The theory of topotactic anion exchange will be discussed in detail, and results of the growth and characterization of numerous films demonstrating the power of this approach will be presented.
5:00 PM - T2.6
Deposition and Properties of Multiferroic Epitaxial Pb(Fe1/2Nb1/2)O3 Thin films by Pulsed Laser Deposition
Li Yan 1 , Jiefang Li 1 , Dwight Viehland 1
1 Materials Science and Engineering Department, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, United States
Show AbstractEpitaxial Lead Ion Niobate (Pb(Fe1/2Nb1/2)O3 or PFN) thin films are deposited on (001), (110) and (111) SrTiO3 substrates with SrRuO3 as bottom electrodes. The structural, ferroelectric and ferromagnetic properties will be reported. The resistivity of PFN thin film can reach up to 10^10 Ω cm; the saturated polarization is increased dramatically comparing with bulk PFN single crystal and ceramics; a weak ferromagnetic moment is measured which is dependent on epitaxial stress; the lattice structures of PFN thin films are different in three substrate orientations.
5:15 PM - T2.7
Non-Linear Optical probing of MultiFunctionality and Phase Transition in PbVO3 Thin Films
Amit Kumar 1 , Sava Denev 1 , Lane Martin 2 , Ramamoorthy Ramesh 2 , Venkatraman Gopalan 1
1 Materials Science and Engineering, Pennsylvania, University Park, Pennsylvania, United States, 2 Materials Science and Engineering, University of California , Berkeley, Berkeley, California, United States
Show AbstractLead vanadate (PbVO3) , a relatively new perovskite material, has been predicted to be a multiferroic exhibiting simultaneous ferroelectric and antiferromagnetic ordering. Experimental confirmation of multiferroicity has been difficult with conventional electrical and magnetic measurements. In this work, nonlinear optical techniques have been employed to study the electrical polarization and magnetic ordering in single phase, fully epitaxial thin films of PbVO3 grown using pulsed laser deposition. This growth realizes the first production of PbVO3 outside of high-temperature and high-pressure techniques through growth of epitaxial thin films on LaAlO3 (001), LaAlO3/Si (001), NdGaO3 (110), and SrTiO3 (001) single crystal substrates. Structural analysis of the PbVO3 thin films using transmission electron microscopy, x-ray diffraction, and Rutherford backscattering spectroscopy reveals films that are single phase, highly crystalline, and have a tetragonally distorted perovskite structure with a = 3.79Å and c = 5.02Å (c/a = 1.32). Using optical second harmonic generation (SHG), we have determined a tetragonal point-group symmetry of 4mm for PbVO3 grown on different substrates which confirms the presence of non-centrosymmetry, as imaged via TEM, which in turn gives rise to electrical polarization. As the film growth direction is along the c-axis which is also the direction of the structural distortion and therefore the electrical polarization in these film, SHG measurements were performed in tilted geometry and used to extract effective nonlinear optical coefficients for the film at different temperatures ranging from 4 K to 400 K. We also show a distinct anomaly in the SHG intensity and nonlinear optical coefficients at ~100 K for these films, which suggest a possible magnetic transition near this temperature. The magnetic symmetry has been analyzed on the basis of the symmetry of the SHG response, and determined to be either G-type or a spin glass system. This matches well with the few theoretical treatments done on PbVO3 to this point which note that both C and G-type antiferromagnetic order are the likely ground states at low temperatures. Theoretical modeling of the SHG response is presented that yields quantitative measurements of effective nonlinear optical coefficients as a function of temperature.
5:30 PM - T2.8
Antiferroelectricity in Multiferroic BiCrO3 Epitaxial Films.
Dae Ho Kim 1 , Ho Nyung Lee 1 , Maria Varela 1 , Hans Christen 1
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show Abstract5:45 PM - T2.9
Effects of Dynamic Strain in Magnetic Films on Piezoelectric Crystals.
Kathrin Dorr 1 , Christian Thiele 1 , Bilani Orkidia 1 , Ludwig Schultz 1
1 , IFW Dresden, Dresden Germany
Show AbstractT3: Poster Session: Multiferroics
Session Chairs
Tuesday AM, November 28, 2006
Exhibition Hall D (Hynes)
9:00 PM - T3.1
Magnetic and Ferroelectric Properties of YMnO3 Epitaxial Thin Films.
Kazuhiro Maeda 1 , Takeshi Yoshimura 1 , Norifumi Fujimura 1
1 , Osaka Prefecture University, Sakai Japan
Show AbstractA material group called multiferroics has attracted considerable attention due to their potential for future computing application. Multiferroics have multiple simultaneous properties such as ferroelectricitiy, ferromagnetism, ferroelasticity and show cross-correlation among the properties. In magnetoferroelectric multiferroics, a magnetic field may control the electric polarization or an electric field may control the magnetization.In this study, we focused on YMnO3, which is a hexagonal RMnO3 compound and has simultaneous antiferromagnetic and ferroelectric properties. Recently, cross-correlation in the magnetic-dielectric properties on hexagonal RMnO3 single crystals including YMnO3 has been reported. In single crystals of YMnO3 and LuMnO3, the dielectric permittivity is largely reduced below the antiferromagnetic Néel point [1]. We examined the relationship between the ferroelectric domain switching and the ordering of magnetic moment using YMnO3 epitaxial films.YMnO3 epitaxial films were deposited by pulsed laser deposition method. To optimize the deposition condition, we analyzed the plasma plume by optical emission spectrometry. It was found that with increasing the laser energy density, the amount of atomic oxygen was increased and the leakage current of the films was decreased. YMnO3 epitaxial films showed distinct ferroelectricity with a spontaneous polarization of 4.2μC/cm2. Moreover the films showed magnetic phase transition near 130K. On the temperature dependence of the maximum dielectric permittivity on the C-V characteristics, which is attributed to the ferroelectric polarization switching, anomaly was observed below the magnetic phase transition near 130K. This result suggests that the ferroelectric polarization switching was suppressed by the ordering of magnetic moment. [1] T. Katsufuji, S. Mori, M. Masaki, Y. Moritomo and H. Takagi: Phys. Rev. B. 64 (2001) 104419.
9:00 PM - T3.10
Photoassisted Polarization Switching in BiFeO3 Thin Films Observed by Terahertz Radiation.
Kouhei Takahashi 1 , Masayoshi Tonouchi 1
1 , Institute of Laser Engineering, Osaka University, Suita, Osaka, Japan
Show AbstractWe have previously reported the first finding of terahertz (THz) radiation from photoconductive switches fabricated on ferroelectric BiFeO3 thin films excited by femtosecond laser pulses [1]. The THz radiation characteristics of BiFeO3 exhibited various intriguing features due to its uniqueness of THz radiation originating from an ultrafast modulation of spontaneous polarization Ps. Here, we have further measured the detailed THz radiation characteristics and observed an interesting phenomenon where carrier excitation triggered by laser illumination seems to greatly enhance the effective electric field applied to the film.Since THz radiation results from the ultrafast modulation of Ps, we can observe THz radiation from BiFeO3 photoconductive switches even under the absence of an external bias electric field Ebias. In other words, the electric field derived from Ps substitutes Ebias, which is essential for THz radiation in the case of nonferroelectric materials. Accordingly, the THz amplitude ETHz measured at zero-bias shows a clear hysteresis similar as the well-known P-E hysteresis curve when we plot ETHz as a function of the initially applied Ebias. Now, although strongly sample dependent, BiFeO3 is known to have a large coercive field compared to the other ferroelectrics [2]. Indeed, the present BiFeO3 thin films grown on (LaAlO3)0.3(Sr2AlTaO6)0.7 substrates did not show a complete saturation of ETHz even when a rather high Ebias of ±200 kV/cm was applied to the film. However, a striking feature was observed when the film was poled under a different circumstance. The two poling treatment we compared here is (a) applying Ebias at dark, which is the usual case, and (b) applying Ebias with light (the light source used here is the second harmonic of a mode-locked Ti:Sapphire laser with a center wavelength of 800 nm, repetition rate of 82 MHz, and pulse width of 100 fs). In the latter case, ETHz showed a complete saturation by applying only Ebias of several 10 kV/cm, which is in contrast to the former case explained above. This implies that carrier excitation by laser illumination enhances the effective electric field applied to the film and promotes the switching of Ps. We also confirmed that an extremely weak laser power of 1 mW is sufficient to trigger such photoassisted polarization switching effect.[1] K. Takahashi et al., Phys. Rev. Lett. 96, 117402 (2006).[2] J. Dho et al., Adv. Mater. 18, 1445 (2006).
9:00 PM - T3.11
Ferroelectric Domain Structure and Switching in Epitaxial BiFeO3 Films with Different Crystallographic Orientations.
M.P. Cruz 1 2 , Y. Chu 1 , F. Zavaliche 1 , P. Yang 1 , G. Pabst 1 , R. Ramamoorthy 1
1 , UC-Berkeley, Berkeley, California, United States, 2 , Centro de Ciencias de la Materia Condensada (CCMC)-UNAM, Ensenada, B.C., Mexico
Show AbstractThe ferroelectric domain structure and polarization switching mechanisms in epitaxial BiFeO3 films grown on (001), (110) and (111) oriented SrTiO3 substrates have been investigated by piezoelectric force microscopy. The ferroelectric polarization vector points toward the SrRuO3 bottom electrode in all films. Four and two polarization variants were observed in films grown on (001) and (110) oriented SrTiO3, respectively. (111) oriented films exhibited only one polarization variant, whose direction is normal to the surface. Polarization switching was investigated by electrically poling the films with a dc bias applied to the conducting scanning probe. The 180° switching mechanism was seen in all three oriented films. 109° switching was observed in the (110) and (001) oriented BiFeO3 films, while the 71° switching was only seen in the (001) oriented films. The large strain in the (001) films associated with ferroelastic switching was reflected in a higher out-of-plane converse piezoelectric response (~60 pm/V) than in the other films. Moreover, since more energy is required to ferroelastically switch the domains, the (001) oriented films showed the largest coercive field as well (~250 kV/cm). The 109°-domain switching in the (110) films was metastable and it relaxed by a further 71° rotation (to complete the 180°-reversal). This relaxation was found to be field and microstructure dependent. This work has been supported in part by ONR, under a MURI program and by LBL-LDRD program.
9:00 PM - T3.12
Domain Structure and Defects in Epitaxial BiFeO3 Films Grown on Vicinal SrTiO3 Substrate.
Qian Zhan 1 , Ying-Hao Chu 1 , Rong Yu 2 , Rasmi R. Das 3 , Dong Min Kim 3 , Chang Beom Eom 3 , Ramamoorthy Ramesh 1
1 , UC Berkeley, Berkeley, California, United States, 2 , Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 , University of Wisconsin, Madison, Madison, Wisconsin, United States
Show Abstract9:00 PM - T3.13
Preparation of BiFeO3 Thin Films on Membrane Structure.
Seiji Nakashima 1 , Kwi-Young Yun 1 , Yoshitaka Nakamura 1 , Masanori Okuyama 1
1 Graduate school of engineering science, Osaka University, Toyonaka, Osaka, Japan
Show AbstractMultiferroic materials which have feroelectricity, ferromagnetism (antiferromagnetism) and ferroelasticity simultaneously have attracted much attention as material for application such as memory, sensors, actuators, and so on. Among them, perovskite BiFeO3 (BFO) is a leading candidate, which shows giant ferroelectric polarization (Pr ~ 152μC/cm2) in thin film form1). Such a huge polarization of BFO thin film is strongly affected by the stress from substrate and bottom electrode, but the mechanism has not been clarified completely yet. In this study, we have investigated influence of the stress from substrate and bottom electrode by depositing BFO thin films on membrane structures. Membrane structure which size is 5mm x 8mm was fabricated by etching Si of Pt(200nm)/TiO2(20nm)/SiO2(600nm)/Si(625μm) substrate using 95oC TMAH (Tetramethyleammonium Hydroxide) (25%) for 12 hr. BFO thin films with a thickness of 250nm on the membrane and Pt/TiO2/SiO2/Si substrate were deposited by pulsed laser deposition (PLD) technique using a ArF excimer laser (λ=193nm). Substrate temperature and oxygen pressure were 450oC and 0.03Torr respectively. XRD patterns show that BFO thin films on the membrane and Pt/TiO2/SiO2/Si substrates were polycrystals of only perovskite phase. (There were no diffraction peaks from non perovskite phase such as Bi2O3 or orthorhombic Bi2Fe4O9.) XRD pattern of BFO thin film on the membrane was slightly shifted to lower angle, compared to that on Pt/TiO2/SiO2/Si substrate. It shows that BFO thin film on the membrane has compressive stress from Pt bottom electrode, which is attributed to the difference of thermal expansion between BFO and Pt. Thermal expansion of Pt/TiO2/SiO2/Si substrate depends mainly on that of Si. However, in the case of the membrane, it depends on that of Pt. On the other hand, thermal expansion coefficient of Si is smaller than that of Pt. Therefore, compressive stress of BFO on the membrane is larger than that on Pt/TiO2/SiO2/Si substrate. Reference1)M.Okuyama, K.Y.Yun and D.Ricinschi, Int. Symp. on Integrated Ferroelectrics, 9-564-I, Honolulu, April, 2006
9:00 PM - T3.14
Structural and Electrical Characteristics of La/Mn Modified BiFeO3 Nanoceramics.
Ram Katiyar 1 , Dillip Pradhan 1 , R. Choudhary 1
1 Department of Physics, University of Puerto Rico, San Juan, PO Box-23343, Puerto Rico, United States
Show Abstract9:00 PM - T3.15
Ferroelectric and Magnetic Properties of La-modified BiFeO3 Thin Films Prepared by the Pulsed Laser Deposition Method
Guanjun Zhang 1 , Jinrong Cheng 1 , Rui Chen 1 , Shengwen Yu 1 , Zhongyan Meng 1
1 , Shanghai University, Sahnghai China
Show Abstract9:00 PM - T3.16
Effect of Stain on Texture in Multiferroic BiFeO3 Thin films Using X-ray Microdiffraction.
Chung Wung Bark 1 , Yang Mo Koo 1 , Nobumichi Tamura 2 , Sang Woo Ryu 1 , Hyun Myung Jang 1
1 Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, Kyungsangbuk-Do, Korea (the Republic of), 2 , Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show Abstract Recently, multiferroic materials, which two or more of the properties of magnetism and ferroelectricity and ferroelasticity coexist, have taken much attention due to the potential technological applications. There has been recent research interest in a number of prototypical magnetic ferroelectrics including BiMnO3, YMnO3, and etc. However, in any cases of the previously reported compounds, either the P–E or the M–H curve has been reported at the room temperature. Only BiFeO3 has both ferroelectricity and ferromagnetism simultaneously at room temperature. The formation, movement and interaction of domains have a largely effect on behavior of a multiferroic. Therefore, it is crucial that the micromechanics of domains and their effect on internal stresses in multiferroics be understood. The BiFeO3 thin films on SrTiO3 (001) substrates fabricated by PLD (Pulsed Laser Deposition) method. The synchrotron radiation source of beam line 7.3.3.2 at the Advanced Light Source (ALS), Lawrence Berkeley National Laboratory, was used for the reflection Laue experiment. The data were analyzed with an indexing software using non-linear least-squares refinement, XMAS (X-ray Microdiffraction Analysis Software). Geometrical calibration parameters were determined by using SrTiO3 crystal beneath thin film. This crystal also used as a reference from strain calculations. The calculated atomic positions which were carried out within a LSDA (Local Spin-Density Approximation) were used. As a result, the crystal orientation and the triaxial deviatoric strain tensor were obtained for every scanned position. In all the scanned grains, the indexation of the Laue patterns show that the grains were confirmed that had a crystal orientation of (001) and others were had the orientation of (101). The local distribution of the deviatoric component the residual strain tensor along the x axis obtained from the two dimensional scan of the top surface was represented. This clearly indicates that the observed residual strain of grains which had a crystal orientation of (001) is quite larger than that of (101). Epitaxial constraint has an effect on crystal structure distortion. Then, the crystal structure is distorted from the rhombohedral along the (001). The integrated average value of residual strain was 6.38 x 10-3 from all of (001) grains and 5.61 x 10-3 from all of (101) grains. (101) texture has the lower strain than (001) texture. The (101) texture is form to provide epitaxial strain relief between substrate and film.
9:00 PM - T3.17
Enhancement of Electrical and Magnetic Properties of Rare Earth doped BiFeO3 Multiferroics
Ratnakar Palai 1 , Suprem Das 1 , P. Dobal 1 , P. Bhattacharya 1 , Ram Katiyar 1 , W. Iwamoto 2 , C. Rettori 2 , P. Pagliuso 2
1 Department of Physics, University of Puerto Rico, San Juan, Puerto Rico, United States, 2 Instituto de Fisica, UNICAMP, Campinas, SP, Brazil
Show AbstractThe feasibility of future spintronic devices using multiferroic BiFeO3, a single phase naturally occurring material, is still debated because of its high leakage current, weak ferroelectricity, and lack of understanding of origin of magnetism. However, alternative approaches of increasing polarization and decreasing the leakage current can be possible by cationic doping with other elements. In order to investigate the effect of doping on the ferroelectric and ferromagnetic properties we have synthesized La-doped BiFeO3 (La- on Bi site) and La and Cr- doped BiFeO3 (La- on Bi site and Cr- on Fe site) in both polycrystalline and epitaxial thin films forms using pulsed laser deposition (PLD). The polycrystalline films were grown on Si/SiO2/TiO2/Pt substrates and the epitaxial films were grown on <100> oriented SrTiO3 substrates. The structural and microstructural studies of these films were carried out using X-ray diffraction technique, micro-Raman spectroscopy, and atomic force microscopy (AFM). It is found that La- substitution enhanced the multiferroic properties of BiFeO3 and reduce the leakage current by four to five order of magnitude at a field 50 kV/cm. Further enhancement of properties were observed by doping in both Bi- and Fe-sites with La- and Cr- respectively. The higher values of polarization and magnetization in epitaxial films compared to polycrystalline counterparts were explained on the basis of the structural studies and epitaxial strain between the film and the substrate.
9:00 PM - T3.18
Integration of Ferroelectric BiFeO3 Thin Film on Semiconductor GaN.
Seung-Yeul Yang 1 , W. Tian 2 , Q. Zhan 1 , Y. Chu 1 , M. Cruz 1 3 , K. Lee 1 , D. Schlom 2 , R. Ramesh 1
1 Materials Science and Engineering, U.C. Berkeley, Berkeley, California, United States, 2 Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania, United States, 3 Centro de Ciencias de la Materia Condensada, CCMC-UNAM, Ensenada , B.C., Mexico
Show AbstractIntegration of ferroelectric thin film with semiconductor leads to a wide variety of device applications such as optoelectronic applications and memory storage devices. More recently, the ferroelectric /semiconductor GaN heterostructure system is being investigated due to the high thermal conductivity, breakdown voltage and chemical and mechanical stability. Perovskite BiFeO
3 (BFO) has attracted great attention due to its large ferroelectric polarization and very high order temperatures (ferroelectric Curie temperature T
c = 1030K), which enables BiFeO
3 to be the most prospective candidate as a ferroelectric layer for high temperature device applications.In the present work, we demonstrate the growth of BiFeO
3 thin film using liquid delivery metalorganic chemical vapor deposition (MOCVD) on (0001) GaN/sapphire substrate by epitaxial SrTiO
3 buffer layers with various orientations. These buffer layers allow the epitaxial BiFeO
3 film growth on GaN, whereas polycrystalline BiFeO
3 films were grown on bare GaN surface. The sharp piezoelectric response and square hysteresis loops were obtained with remanent polarization (P
r) of ~80 μC/cm
2 from (111)BiFeO
3 / (111)SrRuO
3 / (111)SrTiO
3 / TiO
2 / (0001)GaN heteroepitaxial structure. Moreover, the microstructure and electrical properties of directly integrated BiFeO
3 on GaN by using ultra thin buffer layers will be discussed.
This work has been supported by the ONR under a MURI program. The authors acknowledge support of the staff and facilities at the National Center for Electron Microscopy, Lawrence Berkeley National Laboratory.
9:00 PM - T3.19
Enhanced Ferroelectric Properties of Epitaxial BiFeO3 Thin Films on Si.
Rasmi Das 1 , Dong-Min Kim 1 , Seung Hyub Baek 1 , Chang-Beom Eom 1 , Venu Vaithyanathan 2 , Darrell Schlom 2 , Yanbin Chen 3 , Xiaoqing Pan 3 , Florin Zavaliche 4 , Seungyeul Yang 4 , R. Ramesh 4
1 Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States, 2 Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States, 3 Department of Materials Science and Engineering, The University of Michigan, Ann Arbor, Michigan, United States, 4 Department of Materials Science and Engineering, University of California, Berkeley, California, United States
Show Abstract9:00 PM - T3.2
Capacitance Tunability of Magneto-electric Material:Cr2O3 using Ferromagnetic (La,Sr)MnO3 Electrode.
Takeshi Yokota 1 , Takaaki Kuribayashi 1 , Takeshi Shundo 1 , Yasutoshi Sakakibara 1 , Keita Hattori 1 , Manabu Gomi 1
1 Environmental and Materials Engineering, Nagoya Institute of Technology, Nagoya, Aichi, Japan
Show Abstract9:00 PM - T3.20
Synthesis of Multiferroic BiFeO3 Thin Films by Flux-Mediated Epitaxy (FME)
Sung Hwan Lim 1 , Makoto Murakami 1 , Shigehiro Fujino 1 , Nagarajan Valanoor 2 , Manfred Wuttig 1 , Ichiro Takeuchi 1 , Lourdes Salamanca-Riba 1
1 Materials Science and Engineering, University Of Maryland, College Park, Maryland, United States, 2 School of Materials Science, University of New South Wales, Sydney, New South Wales, Australia
Show Abstract We have fabricated multiferroic BiFeO3 thin films by using the novel flux-mediated epitaxy (FME) technique, in which a film grows from flux on the surface. In this method, vapor from a Bi1.1FeO3, target material diffuses into the flux material and solidifies on a predeposited seed layer of BiFeO3. This procedure can reduce the instability of direct phase transformation from the vapor to the solid. High quality single crystalline BiFeO3 thin films were fabricated on SrRuO3 buffered SrTiO3 (001) substrates. To optimize deposition conditions, the combinatorial deposition technique with temperature and composition gradients on the same sample was used. The oxygen pressure and substrate temperature were varied in the ranges of 0.03 – 3 Torr and 600 – 800 °C, respectively. The structural properties of the films were studied using transmission electron microscopy, x-ray diffraction, atomic force microscopy, and energy dispersive x-ray spectroscopy. By using the FME method, we observed marked improvement in the crystallinity of BiFeO3 films. The peak intensity of BiFeO3 in x-ray diffraction increased more than 20% and the lattice constant was closer to the bulk parameter compared to films grown by the normal pulsed laser deposition technique. The grain size increased approximately from 0.2 to 2 μm. The physical properties of the films are being characterized using piezo force microscopy, and SQUID.This work was supported by NSF MRSEC under account No. DMR-05-20471 and the W. M. Keck Foundation.
9:00 PM - T3.24
Structural and Magnetic Properties of Nanogranular BaTiO3-CoFe2O4 Thin Films Deposited by Laser Ablation on Si/Pt Substrates.
J. Barbosa 1 , Bernardo Almeida 1 , J. Mendes 1 , A. Rolo 1 , J. Araújo 2 , J. Sousa 2
1 Physics, Minho University, Braga Portugal, 2 IFIMUP, Physics, Porto University, Porto Portugal
Show AbstractThe synthesis of materials that exhibit simultaneous ferromagnetic and ferroelectric characteristics has been attracting much scientific and technological interest. In these multiferroic materials, the coupling between the magnetic and electric degrees of freedom, the so-called magnetoelectric effect, may give rise to new physical phenomena and applications.Recently, nanostructured multiferroic composites formed by the combination of a piezoelectric ceramic and a magnetostrictive material, such as in the BaTiO3-CoFe2O4 system, have been deposited in a film-on-substrate geometry. In these systems, the elastic interactions between the phases provides the coupling mechanism inducing a magnetoelectric behavior. As a result, the properties and performance of these nanostructures depend critically on the phase morphology and internal stress distribution, which, in turn, are determined by the elastic phase/phase and phase/substrate interactions.In order to address this problem we have deposited thin film composites of cobalt ferrite (CoFe2O4) dispersed in barium titanate (BaTiO3) matrix, with different cobalt ferrite concentrations (from 20% to 70% CoFe2O4), as well as pure barium titanate and cobalt ferrite thin films (end members). The films were prepared by pulsed laser ablation with a KrF excimer laser (wavelength of 248nm), on platinum covered Si(001) substrates. The oxygen pressure during deposition was in the range 0.4mbar - 2mbar, and the substrate temperature was 600C. The films structure was studied by X-ray diffraction and their surface was examined by scanning electron microscopy (SEM). The magnetic properties were measured in a SQUID magnetometer. The results show that the deposited films are polycrystalline with a slight (111) barium titanate phase orientation and (311) CoFe2O4 phase orientation. The relative intensity of the (111) BaTiO3 increases with increasing CoFe2O4 concentration, while the opposite occurs with the (311) peak relative intensity of the CoFe2O4 phase. The grain sizes measured from the X-ray diffraction peak widths, for both phases, are in the range 40nm to 100nm. However, as the concentration of the cobalt ferrite increases, the grain size of the BaTiO3 phase decreases, from 100nm to 30nm, up to 40% CoFe2O4 concentration beyond which the BaTiO3 grain size has an approximately constant value near 40nm. On the other hand the cobalt ferrite grain size does not show a clear trend with increasing cobalt ferrite concentration, fluctuating in the range 30nm to 40nm. Moreover, the surface of the films shows a smooth and uniform morphology, as observed by SEM, with a small density of droplets.The magnetic measurements show an increase of the magnetic moment from the low concentration region where the magnetic grains are more isolated, towards the bulk value that is attained in the pure CoFe2O4 films. The magnetic behavior of the films is discussed in terms of its correlation with the structural properties of the films.
9:00 PM - T3.25
Structural and Multiferroic Properties of La Modified 0.57BiFeO3-0.43PbTiO3 Crystalline Solutions.
Jianguo Chen 1 , Jinrong Cheng 1 , Dengren Jin 1 , Shengwen Yu 1 , Zhongyan Meng 1
1 , Shanghai University, Sahnghai China
Show Abstract9:00 PM - T3.26
Magnetic and Dielectric Phase Transitions in Multiferroic BiFeO3-ReFeO3-BaTiO3 (Dy, La, Ba) Ceramics.
Jeong Kim 1 , Chae Cheon 2 1 , Nam Kim 2 , Pyong Jang 3
1 Digital Display, Hoseo University, Asan Korea (the Republic of), 2 Materials Sci. & Eng., Hoseo University, Asan Korea (the Republic of), 3 Dept. of Physics, Chongju University, ChongJu Korea (the Republic of)
Show AbstractThe materials exhibiting multiple ferroic properties, such as ferroelectricity, ferroelasticity, and ferromagnetism (or antiferromagnetism) in one phase have been named as the multiferroics. Recently the ferroelectromagnetic materials have became widely known due to their potential applications in the memory devices, sensors, and spintronics. The perovskite type materials provide the vast spectrum of electrical properties covering (anti-) ferroelectric, (anti-)ferromagnetic, metallic, semiconductor, and insulator. Hence the combination of these perovskite members could open various routes for achieving the multiferroic properties in one phase material. Residual magnetic moments at 20 Oe and 8 kOe have been measured using vibrating sample magnetometer (VSM) with increasing temperature up to 600oC. The dielectric constant εr and the loss tangent have been measured using impedance analyzer (10kHz~1MHz) in the temperature range of RT~550oC. Neutron diffraction data were collected using HRPD diffractometer at HANARO in Korea Atomic Energy Research Institute. The neutrons from the HANARO reactor were monochromatized by a vertically focusing composite Ge-monochromator to a wavelength of 1.8348Å. The crystal structure was analyzed by the rietveld profile refinement method using a version 3.2 of the program Fullprof. Dielectric and magnetic properties of the xBiFeO3-yReFeO3-zBaTiO3 (Re=La, Dy, Ba) solid solution ceramics at high temperature range of RT~600oC have been characterized. For more understandings of the multiferroic property, the relation between the crystal structure transition, magnetic transition, dielectric transition with increasing temperature have been analyzed. Residual magnetization Mr under the low and high applied magnetic fields (H = 20Oe, 8KOe) and the dielectric properties, εr and tand, with varying measuring frequency and temperature have been characterized using the vibrating sample magnetometer and LCR meter respectively. The neutron diffraction data has been collected at the temperature range of RT ~ 800oC. The low Re content samples (y = 0, 0.025) show one magnetic transition at temperature range of 410~430oC while the high DF concentration samples (y = 0.05) show an additional transition at 250~290oC. The magnetic transition at 410~430oC corresponds to the crystal structural transition to the tetragonal P4mm from the rhombohedral R-3c, at which the BiFeO3 and the DyFeO3 samples lose their antiferromagnetic ordering. The multiferroic properties will be discussed in relation with the phase transitions of magnetic, dielectric, and crystal structures.
9:00 PM - T3.27
Processing and Characterization of LSMO-Based Multiferroic Composite Ceramics.
Andrei Kholkin 1 , G. Song 1 3 , J. Amaral 2 , V. Amaral 2 , Z. Fu 1 , J. Araujo 4 , J. Sousa 4
1 Dept. of Ceramics/CICECO, University of Aveiro, Aveiro Portugal, 3 School of Material Science and Engng., Sothwest University of Science and Technology, Mianyang China, 2 Dept. of Physics/CICECO, University of Aveiro, Aveiro Portugal, 4 Dept. of Physics/CPF, University of Porto, Porto Portugal
Show Abstract9:00 PM - T3.28
Magnetoelectric Properties of Multiferroic Composites with Pseudo 1-3 Type Structure.
Zhan Shi 1 , Ce-Wen Nan 1 , Jie Zhang 1 , Jing Ma 1 , Jing-Feng Li 1
1 Material Science and Engineering, Tsinghua University, Beijing China
Show AbstractA pseudo 1-3 type multiferroic composite consisting of Pb(Zr,Ti)O3 (PZT) rod array (with base) and Terfenol-D/Epoxy matrix was prepared by the dice-and-fill technique. Simple series and parallel mixture rules well described the measured dielectric and piezoelectric constants. Large magnetoelectric coefficients were observed in the pseudo 1-3 type composite, e.g., over 300 mV/cm.Oe below 40 kHz and over 4500 mV/ cm.Oe at resonant frequency. The ME response strongly depends on the magnetostrictive behavior of the matrix and the volume fraction of PZT rods, which gives us two convenient way to modify their magnetoelectric response. For this pseudo 1-3 type multiferroic composite, the remarkable magnetoelectric response and well-developed fabrication technique are advantageous for their practical applications in piezoelectric-magnetoelectric multifunctional devices and large bandwidth magnetic sensors.
9:00 PM - T3.29
Multiferroic Pb(Zr0.53Ti0.47)O3/NiFe2O4 Sol-gel Thin Films.
Shenqiang Ren 1 , Manfred Wuttig 1
1 Dept. of Materials and Science Engineering, University of maryland, college park, College park, Maryland, United States
Show AbstractPhase-separated multiferroic Pb(Zr0.53Ti0.47)O3/NiFe2O4 thin films on (111)Pt/Ti/SiO2/Si substrates were synthesized by a sol-gel spin-coating technique, as evidenced by x-ray diffraction. The use of sol-gel processing ensured good chemical homogeneity and a relatively low crystallization temperature. The dependence of annealing conditions and microstructure evolution of thin films were examined by Environmental scanning electron microscopy, transmission electron microscopy and atomic force microscopy. Obvious multiferroic behavior has been observed in phase-separated and highly resistive Pb(Zr0.53Ti0.47)O3/NiFe2O4 thin films. These show the coexistence of ferroelectricity and magnetism, possess an anomaly of the dielectric constant in the vicinity of the ferromagnetic Curie temperature, and exhibit magnetoelectric coupling at room temperature.
9:00 PM - T3.3
AFM-Based Simultaneous Measurement of Ferroelectric and Ferromagnetic Domains in Multiferroics.
Brian Piccione 1 , John Blendell 1 , R. Garcia 1 , R. Ramesh 2
1 Materials Science and Engineering, Purdue University, West Lafayette, Indiana, United States, 2 Materials Science and Engineering, University of California, Berkeley, California, United States
Show AbstractA BiFeO3-CoFe2O4 sample grown on SrRu03 by pulsed laser deposition was examined using combined MFM and PFM (both lateral and vertical) to determine the effect of crystallographic arrangement on local strain coupling. Simultaneous measurement of local magnetostrictive and piezoelectric response in a multiferroic composite is expected to yield information on the effect of texture on the coupling mechanics of these new materials. The results of the combined measurements will be correlated to predicted results based on FEA, with the goal of aiding design in applications such as nonvolatile multiferroic memory and novel magnetoelectic sensors.
9:00 PM - T3.30
Magnetoelectric Effects In Multiferroic Compounds And Composites.
Junming Liu 1
1 Department of Physics, Nanjing University, Nanjing 210093 China
Show AbstractMagnetoelectric coupling as well established in multiferroic perovskite oxide compounds and piezoelectric-magnetostrictive composites has been receiving attentions due to its unique application potentials in sensing and actuation technologies. In addition, the rich physics underlying the coupling represents one of the hot topics in the community of condensed matters and materials sciences. We report our recent researches on the magnetoelectric coupling effects in multiferroic perovskite oxides and piezoelectric-magnetostrictive composites. First, the phase transitions associated with ferroelectric and magnetic orderings and magnetoelectric coupling in Pb(Fe1/2Nb1/2)O3 (PFN) single crystals were investigated, demonstrating the coupling-induced weak ferromagnetic transitions in PFN at low temperature. Subsequently, we revealed the enhanced ferroelectricity and spin glass behavior of BiFeO3 (BFO) thin films and nanowires. In particular, we observed interesting application potentials of BFO nanowires as photo-catalysts. Furthermore, we developed a series of piezoelectric-magnetostrictive composite structures in both bulk ceramic and thin film forms. The magnetoelectric effects and inverse magnetoelectric effects as observed in these structures are high enough for practical applications in ultra-weak magnetic field sensing at room temperature. The measured data and associated interpretations will be presented in details in this report.
9:00 PM - T3.31
Giant Magnetoelectric Effect in Novel Metglas/PVDF Laminates with Small DC bias
Junyi Zhai 1 , Shuxiang Dong 1 , Jiefang Li 1 , Dwight Viehland 1
1 MSE, Virginia Tech, Blacksburg, Virginia, United States
Show AbstractThe application of magnetoelectric (ME) sensors and devices is mainly restricted by a large DC magnetic bias (400 Oe – 4000 Oe). Here we report thin (< 100 µm) and flexible ME laminates: high-µ Metglas/high-g31 PVDF composites, and their extraordinary ME performances as (i) the required DC magnetic bias is extreme low: ~8 Oe; (ii) giant ME voltage coefficients of 7.2 V/cm-Oe at low-frequency and 310 V/cm Oe at resonance; (iii) high DC magnetic field sensitivity of 8 nT; and (iv) high AC magnetic field sensitivity of < 7 pT at resonance frequency (47.9 kHz).
9:00 PM - T3.32
Polarization Response to Magnetic Field in Model Multiferroics: A Monte Carlo Simulation.
Qichang Li 1 , Junming Liu 1
1 Department of Physics, Nanjing University, Nanjing 210093 China
Show AbstractMultiferroic materials, which possess two or more order parameters such as polarization, magnetization or strain, have been attracting revived interest due to the gigantic magnetoelectric (ME) effect observed in systems such as TbMn2O5 and CoCrO3 etc. In those materials, a startling change or even reversal of electric polarization induced by magnetic field was found. In this work, we report a Monte Carlo simulation on the magnetically driven ferroelectric polarization of a model multiferroic system in which ferroelectric (FE) order and antiferromagnetic (AFM) order coexist. The Hamiltonian of this model system includes the contributions from the ferroelectric subsystem, the AFM Ising subsystem and an intrinsic coupling between the two subsystems. The magnetic and ferroelectric parameters used in the simulation are chosen so that the Curie point for ferroelectric order TC is smaller than the Něel point TN. We investigated the evolution of electric polarization P in responding to magnetic field H below TC. A magnetic field dependence of electric polarization is obtained, similar to experimental results reported earlier. Since only u2 is included in the coupling term, the flips of the nearest-neighboring Ising spins driven by H just influence the amplitude of the electric polarization. On the other hand, the direction of ui in our model is restricted in one axis, which explains why P does not reverse with H in our model. To simulate the reversal of the polarization driven by H, new mechanism of ME coupling should be considered.
9:00 PM - T3.33
Theory of Spin-charge-orbital State in the Frustrated System RFe2O4.
Sumio Ishihara 1 , Makoto Naka 1 , Aya Nagano 1
1 Physics Department, Tohoku University, Sendai Japan
Show Abstract9:00 PM - T3.34
Nanoscale domain control in multiferroic BiFeO3 thin films
Ying-Hao Chu 1 , Qian Zhan 1 , Lane Martin 1 , Maria Cruz 1 , Pei-Ling Yang 1 , Gary Pabst 1 , Florin Zavaliche 1 , Seung-Yeul Yang 1 , Jing-Xian Zhang 2 , Long-Qing Chen 2 , Darrell Schlom 2 , Ramamoorthy Ramesh 1
1 Department of Physics & Department of Materials Science and Engineering, UC Berkeley, Berkeley, California, United States, 2 Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractWe demonstrate an approach to create a 1-dimensional periodic structure of ferroelectric domains in epitaxial BiFeO3 films. By careful control of the growth mechanism for the BiFeO3 and the SrRuO3 bottom electrode, its in-plane lattice parameters have been confined by the underlying DyScO3 (110)O single-crystal substrate enabling the formation of an expitaxial film of (110)O SrRuO3 with a single structural domain. This has been used to provide an anisotropic strain to exclude two of the possible ferroelectric polarization variants and induce a 1-D periodic ferroelectric domain structure in the BiFeO3 films.
9:00 PM - T3.4
Doping Effect on the Charge Ordering in LuFe2O4.
Shigeo Mori 1 , Yoji Matsuo 1 , Y. Horibe 1 , K. Yoshii 2 , N. Ikeda 3
1 Department of Physics, Osaka Prefecture university, Osaka Japan, 2 , JAERI, Hyugo Japan, 3 Deparment of Physics, Okayama University, Okayama Japan
Show Abstract9:00 PM - T3.5
Ferroelectric and Magnetic Characterization of Ferroic Pb(Fe0.5Nb0.5)O3 Ceramics.
Oscar Raymond 1 , Reynaldo Font 2 , Jorge Portelles 2 , Gopalan Srinivasan 3 , Jesús Siqueiros 1
1 Propiedades Opticas, Centro de Ciencias de la Materia Condensada, UNAM, Ensenada, Baja California, Mexico, 2 Física Aplicada, Universidad de la Habana, La Habana, Ciudad de la Habana, Cuba, 3 Physics Department, Oakland University, Rochester, Michigan, United States
Show Abstract9:00 PM - T3.6
Magnetic and Dielectric Properties of Multiferroic TbMnO3 Nanoparticles.
S. Kharrazi 1 , S. Gosavi 1 , S. Kulkarni 1 , Darshan Kundaliya 2 , S. Ogale 2 , T. Venkatesan 2 , S. Park 3 , S. Cheong 3 , J. Urban 4
1 DST Unit on Nanoscience, Department of Physics, University of Pune, Pune India, 2 CSR, Department of Physics, University of Maryland, , College park, Maryland, United States, 3 Department of Physics, Rutgers University, Piscataway, New Jersey, United States, 4 Department of Inorganic Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft , D-14195 Berlin (Dahlem) Germany
Show Abstract9:00 PM - T3.7
Multiferroic Behavior in Barium Hexaferrite Probed with Optical Second Harmonic Generation
Eftihia Vlahos 1 , Sava Denev 1 , Venkatraman Gopalan 1 , Tsuyoshi Kimura 2
1 Materials Science and Engineering, Penn State University, University Park, Pennsylvania, United States, 2 Bell Laboratory, Lucent Technologies, Berkeley Heights, New Jersey, United States
Show AbstractHexaferrite Ba0.5Sr1.5Zn2Fe12O22 is a very promising material, which exhibits significant magneto (ME) effect, that is, the generation of electric polarization (magnetization) by the application of magnetic (electric) field. It was recently reported that the ferroelectric polarization direction in this material can be rotated by an externally applied magnetic field. Using second harmonic generation (SHG), the magnetic point group symmetries and phase transitions under magnetic fields are determined. Theoretical modeling of the SHG behavior is carried out yielding quantitative information about its nonlinear optical coefficients and its changes with temperature and magnetic fields. SHG allows a clean separation of the magnetic and ferroelectric contributions to the multiferroic system.
9:00 PM - T3.8
Improvement of the Crystallinity of BiFeO3 Thin Films Prepared by MOCVD.
Yuzo Tasaki 1 , Toshiaki Kanoko 2 , Shuji Yoshizawa 2
1 , Toshima MFG Co.,Ltd., Higashimatsuyama, Saitama, Japan, 2 , Meisei Univ., Hino, Tokyo, Japan
Show Abstract9:00 PM - T3.9
Synthesis, Structure and Magnetism of BiFeO3 thin films on (LaAlO3)0.3(Sr2AlTaO6)0.7 (100) Substrates.
Dhanvir Rana 1 , K. Takahasni 1 , K. Mavani 1 , I. Kawayama 1 , H. Murakami 1 , M. Tonouchi 1
1 Institute of Laser Engineering, Osaka University, Osaka, Osaka-fu, Japan
Show AbstractA recent upsurge in research on room temperature multiferroic (antiferromagnetic and ferroelectric) BiFeO3 has been motivated by the observation of enhanced ferroelectricity and ferromagnetism in epitaxial thin films [1]. Some of these properties being reported to be thickness dependent remains an issue of contention and deserve further extensive investigations [2]. Furthermore, most of reported studies on BiFeO3 have been performed on the thin films deposited on SrTiO3 substrates. Recently, pure and Mn-doped BiFeO3 thin films were deposited on ((LaAlO3)0.3(Sr2AlTaO6)0.7 (100) [LSAT] single crystal substrates [3]. This offers a further prospect to investigate the multiferroic properties of BiFeO3 thin films in varying epitaxial strain states induced by LSAT substrate. In the present work, we have synthesized BiFeO3 thin films of varying thickness, ranging from 40 nm – 500 nm, on LSAT (100) single crystal substrates, using pulsed laser deposition of a Bismuth-rich, Bi1.1FeO3, multiphase target. We, for the first time, have observed a thin film thickness dependent structural transition from a monoclinically distorted tetragonal phase at a thickness of 110 nm to a rhombohedral phase at a thickness of 80 nm. It is further shown that the in the mixed structural phase region of 80 nm – 110 nm thickness, the phase fraction of rhombohedral structure can be enhanced significantly by increasing the post-deposition O2 annealing pressure from 0.5 kOe to 40 kOe. The room temperature magnetic properties of these films were found to be dependent on thickness – the magnetization increases from 0.04 µB/f.u. for 200nm thin film to 0.14 µB/f.u. for 70nm thin film. In addition for 110 nm thin films, the spontaneous magnetization of the film annealed in ~0.5 kPa O2 pressure (having tetragonal structure) is lesser than that of the film annealed in ~40 kPa O2 pressure (having mixed phase of tetragonal and rhombohedral structures), thus, suggesting that the magnetic properties BiFeO3 films are also dependent on the structure.References - [1]. Wang et al., Science 299, 1719 (2003). [2]. Eerenstein et al., Science 307, 1203a (2005); Wang et al., Science 307, 1203b (2005).[3]. K. Takahashi and M. Tonouchi, Jpn. J. Appl. Phys. (in Press, 2006); K. Takahashi, N. Kida and M. Tonouchi, Phys. Rev. Lett. 96, 117402 (2006).
Symposium Organizers
Venkatraman Gopalan The Pennsylvania State University
Jon-Paul Maria North Carolina State University
Manfred Fiebig Max-Born-Institut
Ce-Wen Nan Tsinghua University
T4/W4: Joint Session: Capacitors
Session Chairs
Tuesday AM, November 28, 2006
Room 302 (Hynes)
9:30 AM - **T4.1/W4.1
An Engineering Perspective: Toward Temperature Insensitive Electric-Field Tunable Material and Devices.
Steven Tidrow 1 , Frank Crowne 1 , Arthur Tauber 1 , Daniel Potrepka 1 , Steven Weiss 1 , Bernie Rod 1
1 Sensors & Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, Maryland, United States
Show AbstractRecently there has been much interest in electric-field tunable dielectric materials, many from the perovskite family, for use in phase shifters for microwave electronic scanning antenna arrays and for frequency agile components like electric-field tunable filters. Materials that are highly electric-field tunable are typically high dielectric constant materials, ferroelectric or anti-ferroelectric, that are, at least in bulk form, quite temperature sensitive and can be quite lossy with respect to microwave radiation. To reduce temperature sensitivity and microwave losses, these materials are often used in the paraelectric regime, in bulk form, or used as thin films. For operation in the paraelectric regime, atomic substitutions are made in the perovskite structure to drive the Curie temperature to well below the minimum device operating temperature, moreover, additions are often made to improve the material figure of merit through reduction of losses. In both cases, such substitutions and additions lead to materials with significantly reduced tunability, for a given electric-field strength, that may result in poorer device performance especially at higher operating temperatures even though the material may have a higher figure of merit. Thin films, which at present appear to be the preferred configuration for fabrication of devices, are typically nearly temperature insensitive with significantly reduced values of both dielectric constant and tunability. While the reduced dielectric constant is useful from a device perspective, the reduced tunability results in reduction of electrode spacing, higher electric-field strengths (even though lower driving voltages may be used) and ultimately reduced power handling capability. We at the Army Research Laboratory, Sensors and Electron Devices Directorate, have been using a different approach to overcoming the various issues associated with electric-field tunable material and devices. From a material engineering perspective, we have fabricated highly electric-field tunable materials that possess lower dielectric constants, reasonable losses and properties that are nearly temperature insensitive over a large temperature range, -50 to 125 °C. Further, from a device engineering perspective, for enabling a low cost electronic scanning antenna technology, we have been developing a variable true time delay device structure and architecture that may provide significant advantages over a phase shifter technology. In this presentation, we will review, from an engineering perspective, material and device trade-offs, discuss these new highly electric-field tunable nearly temperature insensitive materials as well as compare phase shifter and variable true time delay architectures for achieving an affordable electronic scanning antenna technology.
T5: Bismuth Ferrite and Derivatives
Session Chairs
Tuesday PM, November 28, 2006
Room 309 (Hynes)
9:30 AM - T5.1
Planar Electrode Piezoresponse Force Microscopy to Study Ferroelectric Switching in BiFeO3.
Padraic Shafer 1 , Florin Zavaliche 1 2 , Ying-Hao Chu 1 2 , R. Ramesh 1 2
1 Materials Science & Engineering, University of California, Berkeley, California, United States, 2 Physics, University of California, Berkeley, California, United States
Show AbstractThe coupling of ferroelectric and magnetic order parameters in multiferroic systems is an important phenomenon with exciting technological implications for integrating magnetic devices into microelectronic circuits. Various forms of scanning probe microscopy (SPM) have been used to observe and even manipulate the nanoscale domains that are typically found in magnetoelectric thin films, but existing methods are limited in their ability to characterize the dynamic processes that occur during domain orientation switching. To remedy this limitation, we have developed the technique of planar electrode piezoresponse force microscopy (PE-PFM). Our method relies upon epitaxial, conductive electrodes embedded into the plane of a ferroelectric thin film in order to decouple the electrical stimulus from the SPM cantilever-tip assembly that measures the piezoresponse. SrRuO3 electrodes were defined by photolithography to examine BiFeO3 films, both of which were prepared by pulsed laser deposition on SrTiO3, DyScO3, or GdScO3 single-crystal substrates at temperatures between 600-750 °C. The epitaxial nature of the system permits the domain structure of BiFeO3 to be tailored by the strain, anisotropy, and crystalline orientation of the substrate. Decoupling the stimulus from the SPM tip allows electric fields to be applied within the scanning plane so that time-resolved images can be captured as domain wall motion evolves within that plane. By applying dc electric field pulses (0.01-1000 ms; 25-600 kV/cm) to a BiFeO3 film through embedded SrRuO3 electrodes, we were able to observe switched ferroelectric domains nucleate on one electrode and subsequently grow toward the other electrode. Because PE-PFM does not require a conductive coating that enlarges the SPM tip, our technique offers PFM images with higher spatial resolution than the traditional biased-tip approach. Additionally, the planar electrode setup permits magnetoelectric characterization to be performed as a function of time and electric field strength by magnetic force microscopy, Kerr microscopy, or photoemission electron microscopy using linear or circular dichroism. BiFeO3 is already well known to be multiferroic, having previously been established as a G-type antiferromagnet, with Fe magnetic moments coupled ferromagnetically within pseudocubic (111) planes and antiferromagnetically between planes, where [111]C is the ferroelectric polarization direction. We observed domain switching in BiFeO3 grown on DyScO3(110)O to be predominantly ferroelastic, thus opening the possibility of electrically controlling the orientation of antiferromagnetic ordering in BiFeO3. This effect could be used to switch the magnetic polarization of a ferromagnet that is exchange-biased to BiFeO3. The electrode layout of the PE-PFM setup provides a versatile framework for non-destructive, high-resolution (spatial and temporal) characterization and control of magnetoelectric structures.
9:45 AM - T5.2
Computer Simulation of Ferroelectric Domain Morphologies of Epitaxial BiFeO3 Thin Films.
Jingxian Zhang 1 , Samart Choudhury 1 , Yulan Li 1 3 , Ying-Hao Chu 2 , Florin Zavaliche 2 , Quanxi Jia 3 , Darrell Schlom 1 , Ramamoorthy Ramesh 2 , Long-Qing Chen 1
1 Department of Materials Science and Engineering, Pennsylvania State University, State College, Pennsylvania, United States, 3 MST-STC, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 Department of Materials Science and Engineering and Department of Physics , University of California, Berkeley, California, United States
Show AbstractT4/W4: Joint Session: Capacitors
Session Chairs
Tuesday PM, November 28, 2006
Room 302 (Hynes)
10:00 AM - **T4.2/W4.2
Integrated BST Tunable Dielectrics for Frequency Agile GHz Applications.
Paul Clem 1 , Jennifer Sigman 1 , Patrick Finnegan 1 , Chris Nordquist 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractFor development of compact RF electronics with frequency agile properties, materials integration of low loss tunable dielectrics with high conductivity metals is necessary. Methods for integration of tunable dielectric [(Ba,Sr)TiO3, BST] thin films on substrates including silicon, alumina, silicates, and metal foils will be presented. Reducing atmosphere approaches to enable BST integration on base metal foils and electrodes will be discussed, including the interplay between metal reduction and oxide defect chemistry. In thin film form, epitaxial and columnar-grained BST films have been observed to display significantly higher permittivities and tunabilities than otherwise identically-processed randomly oriented, polycrystalline films. This effect will be discussed in relation to the grain size, grain morphology, and domain orientation of the BST films, as determined by microscopy, x-ray diffraction and Raman spectroscopy. Phase shift and Q results for interdigitated capacitors of these films in the 1-10 GHz range will be reported, along with approaches to more temperature-stable tunable capacitor properties. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy''s National Nuclear Security Administration under contract DE-AC04-94AL85000.
T5: Bismuth Ferrite and Derivatives
Session Chairs
Tuesday PM, November 28, 2006
Room 309 (Hynes)
10:00 AM - **T5.3
Multifunctional Oxide Heterostructures.
Ramesh Ramamoorthy 1
1 Depts. of Materials Science and Engineering and Physics, University of California - Berkeley, Berkeley, California, United States
Show AbstractComplex perovskite oxides exhibit a rich spectrum of functional responses, including magnetism, ferroelectricity, highly correlated electron behavior, superconductivity, etc. The basic materials physics of such materials provide the ideal playground for interdisciplinary scientific exploration. Over the past decade we have been exploring the science of such materials (for example, colossal magnetoresistance, ferroelectricity, etc) in thin film form by creating epitaxial heterostructures and nanostructures. Among the large number of materials systems, there exists a small set of materials which exhibit multiple order parameters; these are known as multiferroics. Using our work in the field of ferroelectric and ferromagnetic oxides as the background, we are now exploring such materials, as epitaxial thin films as well as nanostructures. Specifically, we are studying the role of thin film growth, heteroepitaxy and processing on the basic properties as well as magnitude of the coupling between the order parameters. A very exciting new development has been the discovery of the formation of spontaneously assembled nanostructures consisting of a ferromagnetic phase embedded in a ferroelectric matrix that exhibit very strong coupling between the two order parameters. This involves 3-dimensional heteroepitaxy between the substrate, the matrix perovskite phase and spinel phase that is embedded as single crystalline pillars in this matrix. In this talk I will describe to you some aspects of such materials as well as the scientific and technological excitement in this field.
T4/W4: Joint Session: Capacitors
Session Chairs
Tuesday PM, November 28, 2006
Room 302 (Hynes)
10:30 AM - T4.3/W4.3
Fabrication of Frequency Agile Microwave Circuits Using (Ba,Sr)TiO3 Thin Film Capacitors
Jennifer Sigman 1 , Paul Clem 1 , Chris Nordquist 1 , Patrick Finnegan 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractNew materials and new integration schemes are vital to the continued development and improvment cellular, satellite and radar communication systems. We report on our efforts to integrate tunable dielectric (Ba,Sr)TiO3 (BST) thin films into frequency agile microwave circuits. We focus on depositing BST on alumina and through-wafer via hole substrates. Using through-wafer via holes increases the variety of devices that can be realized, but adds complexity for materials integration because the via material is a copper-tungsten alloy. By controlling the processing parameters, namely temperature and oxygen partial pressure, we have successfully deposited quality BST on alumina and through wafer via hole substrates by chemical solution deposition without secondary phases. Initial phase shifter devices have also been successfully fabricated and tested. Both the film properties and device properties are discussed.
T5: Bismuth Ferrite and Derivatives
Session Chairs
Tuesday PM, November 28, 2006
Room 309 (Hynes)
10:30 AM - T5.4
Effects of BiFeO3 Deposition on SrTiO3 Substrates.
Mary Ellen Zvanut 1 , Brian Lassiter 1 , Gregg Janowski 2 , Leonard Brillson 3
1 Department of Physics, University of Alabama at Birmingham, Birmingham, Alabama, United States, 2 Department of Materials and Mechanical Enineering, University of Alabama at Birmingham, Birmingham, Alabama, United States, 3 Center for Materials Research, Ohio State University, Columbus, Ohio, United States
Show AbstractT4/W4: Joint Session: Capacitors
Session Chairs
Tuesday PM, November 28, 2006
Room 302 (Hynes)
T5: Bismuth Ferrite and Derivatives
Session Chairs
Tuesday PM, November 28, 2006
Room 309 (Hynes)
10:45 AM - T5.5
Size Effects in Multiferroic BiFeO3 Thin Films.
Ying-Hao Chu 1 , Tong Zhao 1 , Qian Zhan 1 , Florin Zavaliche 1 , Maria Cruz 1 , Pei-Ling Yang 1 , Lane Martin 1 , Kilho Lee 1 , Seung-Yeul Yang 1 , Wei Tian 2 , Darrell Schlom 2 , Ramamoorthy Ramesh 1
1 Department of Physics & Department of Materials Science and Engineering, UC Berkeley, Berkeley, California, United States, 2 Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractT4/W4: Joint Session: Capacitors
Session Chairs
Tuesday PM, November 28, 2006
Room 302 (Hynes)
11:15 AM - **T4.4/W4.4
BST Technology for RF/Microwave Applications.
Robert York 1
1 , University of California - Santa Barbara, Santa Barbara, California, United States
Show AbstractSince the 1990s there has been significant progess in developing high-k, polar and non-polar materials such as (Ba,Sr)TiO3 (BST) and Bi1.5Zn1.0Nb1.5O7 (BZN). BST thin-films have been realized with properties that are especially attractive for high-frequency applications, including: High dielectric constant (200-300): useful for small-area bypass or AC decoupling capacitors Field-dependent permittivity: as much as 3:1 variation in permittivity or capacitance as a function of applied voltage, useful for tunable RF circuits such as phase-shifters, filters, and (VCOs).“Fast” polarization response: allows for rapid tuningGood breakdown fields: typically >1MV/cm, allowing for large bipolar voltage swings and hence good power handling.Reasonable Loss Tangents: typical loss tangents of tan δ < 0.02 up to 10GHz and higher.Combined with a simple manufacturing process and high-quality insulating substrates, BST-based voltage-variable capacitors (varactors) can provide a compelling alternative to semiconductor-based varactors for highly-integrated RF/Microwave circuits. Several companies now provide products for RF applications based on thin-film BST. This talk will review progress in this area, potential applications and RF insertion points in wireless communications, examples of commercial products, and remaining challenges.
T5: Bismuth Ferrite and Derivatives
Session Chairs
Tuesday PM, November 28, 2006
Room 309 (Hynes)
11:30 AM - T5.6
Exchange Bias and Spin Valves Using BiFeO3 Thin Films.
Shigehiro Fujino 1 , Makoto Murakami 1 , Jaeson Hattrick-Simpers 1 , S. Lim 1 , J. Higgins 2 , Lourdes Salamanca-Riba 1 , S. Lofland 3 , Munfred Wuttig 1 , Ichiro Takeuchi 1 2
1 Materials science and engineering, University of Maryland, College Park, Maryland, United States, 2 Center for Superconductivity Research, University of Maryland, College Park, Maryland, United States, 3 Department of Physics and Astronomy, Rowan University, Glassboro, New Jersey, United States
Show AbstractT4/W4: Joint Session: Capacitors
Session Chairs
Tuesday PM, November 28, 2006
Room 302 (Hynes)
11:45 AM - **T4.5/W4.5
Ferroelectric/electrode Interface: ab initio Description and Impact on the Film Properties.
Alexander Tagantsev 1 , Guido Gerra 1 , Nava Setter 1
1 IMX Ceramics Laboratory, Swiss Federal Institute of Technology (EPFL), Lausanne Switzerland
Show AbstractExperimental studies of ferroelectrics have provided ample evidence for the impact of the ferroelectric/electrode interface on different properties of ferroelectric capacitors. As theoretically demonstrated, it is this impact that can shift the transition temperature of ferroelectric thin films or impede the transition itself [1-4], smear anomalies (e.g., the singularity of the dielectric permittivity) associated with the phase transition [5,6], and promote ferroelectric switching[7]. However, despite an appreciable progress in the theoretical description of the impact of ferroelectric/electrode coupling on the properties of ferroelectric films, one is to face serious problems concerning the practical use of the results obtained. First, most of the results have been obtained in terms of the continuous Landau-Ginsburg phenomenological framework which has been used at spatial scales which are too small to justify its applicability. Second, the few relevant results of first principles calculations have been obtained for systems which are too small to be (at least presently) of practical interest.In this paper, first, we present the results of our ab initio theoretical treatment of the BaTi03/SrRu03 interface and of its impact on the ferroelectric properties of ultrathin ferroelectric thin films. Specifically, we demonstrate that in the case of metal-oxide electrodes a new mechanism of ferroelectric-polarization screening is possible. Within this mechanism, due to the ionic polarizability of the electrode, bound polarization charges can be screened “in situ” by the free charge carriers of the latter.In the second part of the talk, we formulate a phenomenological approach which, on one hand is free from the aforementioned applicability problem, and, on the other hand, enables the use o the results of ab initio calculations to model the properties of relatively thick ferroelectric films. [1] R. Kretschmer and K. Binder, Phys. Rev. B v.20, 1065 (1979).[2] J. Junquera and P. Ghosez, Nature v.422, 506-50(2003).[3] G. Gerra, A. K. Tagantsev, N. Setter, and K. Parlinski, Physical Review Letters v.96 (2006).[4] N. Sai, A. M. Kolpak, and A. M. Rappe, Phys. Review B v.72, 020101-4 (2005).[5] M. D. Glinchuk and A. N. Morozovska, J. of Phys. Conden. Matt. v.16, 3517-3531 (2004).[6] A. M. Bratkovsky and A. P. Levanyuk, Phys.Rev. Lett. v.94, 107601 (2005).[7] G. Gerra, A. K. Tagantsev, and N. Setter, Phys. Rev.Lett.v.94, 107602 (2005).
T5: Bismuth Ferrite and Derivatives
Session Chairs
Tuesday PM, November 28, 2006
Room 309 (Hynes)
11:45 AM - T5.7
Tunnel Magnetoresistance and Exchange Bias with Multiferroic BiFeO3 Epitaxial Thin Films.
Helene Bea 1 , Manuel Bibes 2 , Karim Bouzehouane 1 , Stéphane Fusil 1 , Cyrile Deranlot 1 , Eric Jacquet 1 , Gervasi Herranz 1 , Agnès Barthélémy 1 , Albert Fert 1 , Bénédicte Warot-Fonrose 3 , Salia Chérifi 4
1 , Unité Mixte de Physique CNRS/Thales, Palaiseau France, 2 , Institut d'Electronique Fondamentale, Orsay France, 3 , CEMES-CNRS, Toulouse France, 4 , Laboratoire Louis Néel, Grenoble France
Show AbstractMultiferroic materials display simultaneously ferroelectric and ferro- or antiferromagnetic orders. The coupling between the two order parameters – i.e. reversing the electric polarization by a magnetic field and the magnetization by an electric field - is very interesting from the point of view of fundamental physics, and could also bring additional functionalities in spintronics and other fields. One of the best candidates for room temperature applications is BiFeO3 (BFO) which shows ordered states at high temperatures (it is antiferromagnetic at T < TN = 647K and ferroelectric at T < TC = 1043K). Examples of spintronics devices using an antiferromagnetic multiferroic (AFM) have been proposed by Binek and Doudin [1]. This magnetic tunnel junction (MJT) device takes advantage of the exchange coupling between a multiferroic AFM tunnel barrier and the ferromagnetic electrodes in order to obtain a tuning of the magnetic state (parallel or antiparallel configuration of the magnetizations of the ferromagnetic electrodes) of the junction by an electric field. Prerequisites are then to obtain thin films of the AFM with very small roughness, with good tunnel properties and a large tunnel magnetoresistance in this antiferromagnetic tunnel barrier. Another condition is to conserve the ferroelectric character at the scale of 2 nm and to have an exchange bias between the AFM tunnel barrier and the ferromagnetic electrode.We have optimized the growth of very thin films of BFO on La2/3Sr1/3MnO3 (LSMO) [2] and studied their magnetic and ferroelectric properties. Notably, we have checked the conservation of the ferroelectric character of such BFO thin films down to 2 nm [3]. In LSMO/BFO/Co tunnel junctions, we have obtained a TMR effect of 20% at low temperature. The positive sign of the TMR, corresponds to a positive value of the Co polarisation at the interface with BFO, in sharp contrast with the negative sign found for the Co polarisation at the interface with SrTiO3, TiO2 and LaAlO3.We have taken advantage of the antiferromagnetic spin structure of a BFO film (as evidenced by X-ray linear magnetic dichroism experiments) to induce a sizeable (~50 Oe) exchange bias on a ferromagnetic film of CoFeB, at room temperature. Perspectives of these findings for multiferroics-based spintronics devices will be discussed.[1] Ch. Binek and B. Doudin, J. Phys.: Condens. Matter 17, L39 (2005)[2] H. Béa et al.; Appl. Phys. Lett., 88, 062502 (2006) and to be published in Phys. Rev. B[3] H.Béa et al.; Jpn. J. Appl. Phys. Express letters, 45, L187 (2006)
12:00 PM - T5.8
Microwave Responce from Multiferoic Thin Films.
Peter Petrov 1 , Hsin-I Chien 1 , Neil Alford 1 , Vaijayanti Palkar 2 , K. Prashanthi 3 , S. Bhattacharya 2
1 Centre for Physical Electronics and Materials, London South Bank University, London United Kingdom, 2 , Tata Institute of Fundamental Reasearch, Mumbai 400005 India, 3 , Indian Institute of Technology Bombay, Mumbai 400076 India
Show AbstractT4/W4: Joint Session: Capacitors
Session Chairs
Tuesday PM, November 28, 2006
Room 302 (Hynes)
12:15 PM - **T4.6/W4.6
Aerosol Deposition Method for Low Temperature Ceramic Fabrications.
Takaaki Tsurumi 1 , Jun Akedo 2
1 Graduate School of Science and Engineering, Tokyo Institute of Technology, Meguro, Tokyo, Japan, 2 Advanced Manufacturing Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaragi, Japan
Show AbstractT5: Bismuth Ferrite and Derivatives
Session Chairs
Tuesday PM, November 28, 2006
Room 309 (Hynes)
12:15 PM - T5.9
Terahertz Radiation from Manganese-doped Multiferroic BiFeO3 Thin Films.
Kouhei Takahashi 1 , Masayoshi Tonouchi 1
1 , Institute of Laser Engineering, Osaka University, Suita, Osaka, Japan
Show AbstractPerovskite BiFeO3 is a promising material showing multiferroism at room temperature (ferroelectricity below 1100 K and antiferromagnetism below 640 K) and exhibiting an extremely large spontaneous polarization Ps in thin film form. Previously, we have reported the first observation of terahertz (THz) radiation from BiFeO3 thin films via an ultrafast modulation of Ps triggered by an illumination of femtosecond laser pulses [1]. Considering the multiferroic property of BiFeO3, the next approach will be the control of THz radiation characteristics using magnetic field. However, since BiFeO3 shows a spiral G-type antiferromagnetic ordering, the spontaneous magnetization Ms is extremely small and the magnetoelectric coupling is assumed to be weak [2]. In order to modify such magnetic structure, cation doping has shown great effectiveness. In fact, we have observed a gradual increase of Ms with increasing manganese concentration in manganese-doped Bi1-xFexMnO3 (x = 0, 0.05, and 0.2) thin films, which however, was accompanied by an increase of electric conductivity. This increased conductivity inhibited the ferroelectric measurement using a conventional ferroelectric tester, which questions the presence of ferroelectricity in these manganese-doped films. In the present work, we have measured the THz radiation characteristics of such Bi1-xFexMnO3 thin films and examined how the increased magnetization and conductivity affect their THz radiation property.Despite the uncertainty of ferroelectricity described above, we observed THz radiation from Bi1-xFexMnO3 thin films even under zero-bias voltage and the radiated THz pulses reversed its phase depending on the polarity of the initially applied voltage. This provides a ferroelectric peculiarity of a memory effect representing that the present Bi1-xFexMnO3 thin films actually exhibit ferroelectricity in spite of the enhanced conductivity. Additionally, this feature also demonstrates that the present THz radiation technique can be a good method to judge the presence of ferroelectricity in high-conductive samples, which is in contrast with the conventional ferroelectric testers where an appropriate evaluation becomes difficult for samples with relatively high conductivity. At the meeting, we will also show how the THz radiation characteristic is affected by magnetic field.[1] K. Takahashi et al., Phys. Rev. Lett. 96, 117402 (2006).[2] C. Ederer et al., Phys. Rev. B 71, 060401(R) (2005).
12:30 PM - T5.10
Band Gaps and Schottky Barrier Heights of BiFeO3.
John Robertson 1 , Stewart Clark 2
1 Engineering, Cambridge University, Cambridge United Kingdom, 2 Physics, Durham University, Durham United Kingdom
Show AbstractT4/W4: Joint Session: Capacitors
Session Chairs
Tuesday PM, November 28, 2006
Room 302 (Hynes)
12:45 PM - T4.7/W4.7
Micro-contact Printed Thin Film Capacitors.
Song-Won Ko 1 , Hajime Nagata 1 , Eunki Hong 1 , Clive Randall 1 , Susan Trolier-McKinstry 1 , Pascal Pinceloup 2 , Mike Randall 2 , Aziz Tajuddin 2
1 Materials Science and Engineering, Penn State, University Park, Pennsylvania, United States, 2 , Kemet Electronics Corporation, Fountain Inn, South Carolina, United States
Show AbstractThere is an ongoing need to develop new technologies to enable further down-scaling of layer thicknesses in multilayer ceramic devices, particularly in multilayer capacitors (MLC). There are about 1012 MLC prepared annually. Currently, they are made by tape casting powder slurries, screen-printing, and laminating. In order to prepare a thin film version of such a capacitor, it is essential to demonstrate films with high dielectric constants (>1000) over a wide temperature range, stacking of these films into a multilayer configuration, and an inexpensive means of assembling the films. This paper will demonstrate chemical solution deposited BaTiO3 films on Ni foils with permittivities >1500 down to film thicknesses <150 nm with good temperature stability. Micro-contact printing of chemical solutions of both the dielectric and electrode layers was explored as an economical means of preparing patterned thin film-based MLC without requiring photolithography. For this purpose, methanol/acetic acid-based BaTiO3 solutions were spun onto polydimethylsiloxane stamps, printed onto substrates, pyrolyzed, and crystallized. Normal metal and oxide electrodes have both been investigated. The line edge roughness produced this way was on the order of a tenth of a micron, which should enable very small margins. The printed layer thickness was also very uniform. Multilayer stacking was also demonstrated. Consequently, microcontact printing appears to be an interesting alterative means of preparing MLC with layer thicknesses in the range of ≤0.2 μm.
T5: Bismuth Ferrite and Derivatives
Session Chairs
Tuesday PM, November 28, 2006
Room 309 (Hynes)
12:45 PM - T5.11
Dichroism and Electromagnetic Coupling in BiFeO3 Films.
Mikel Barry 1 , Tong Zhao 1 , Andreas Scholl 2 , Florin Zavaliche 1 , Kilho Lee 1 , Ying-Hao Chu 1 , Maria Cruz 1 , Andrew Doran 2 , Pu Yu 1 , Ramamoorthy Ramesh 1
1 , University of California, Berkeley, Berkeley, California, United States, 2 Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley, California, United States
Show AbstractBiFeO3 is an exciting new material because it is both a multiferroic and lead-free replacement for ferroelectric memory cells, piezoelectric sensors, and actuators. We are investigating the possibility of coupling between ferroelectricity (FE) and antiferromagnetism (AFM) in epitaxial thin films of this system by using photoelectron emission microscopy (PEEM). Combining PEEM with x-ray linear dichroism (XLD) based images allows high spatial resolution along with elemental and chemical specificity and surface sensitivity. FE-AFM coupling is expected in BiFeO3 because the magnetization vectors are approximately perpendicular to the polarization direction. If the polarization direction is changed by non-180 degree domain reversal, we expect the antiferromagnetism to follow. PEEM measurements were performed before and after the ferroelectric state in micron-sized regions of the film were identified and switched by a piezoforce microscope (PFM). The temperature dependent measurements reveal a strong change in XLD as the temperature is raised to and beyond the Neel temperature due to separable contributions from both the antiferromagnetic state and structural distortion (i.e., due to ferroelectricity). These results strongly suggest the possibility of controlling antiferromagnetic order with applied electric fields and are the precursors to electrically controlled magnetic devices. This work is supported by an LBL-LDRD program and by the ONR under a MURI program.
T6: Single Phase Multiferroics
Session Chairs
Tuesday PM, November 28, 2006
Room 302 (Hynes)
2:30 PM - **T6.1
The Ferroelectric Transition and Magnetoelectric Coupling in Hexagonal Manganites
Thomas Palstra 1
1 Materials Science Centre, University of Groningen, Groningen Netherlands
Show AbstractThe hexagonal manganites RMnO3 exhibit multiferroic behavior below the magnetic ordering of the Mn- or rare earth R-sublattice ordering. In this talk I will address two aspects: first, the nature of the ferroelectric transition at Tc~1000K, and second, the strength of the magnetoelectric coupling. -We have carried out systematic investigations at high temperature to determine the nature of the ferroelectric transition. Our structural investigations show the relationship between the lattice tripling, which takes place above Tc, and the ferroelectric distortion. In fact, the nature of the lattice tripling determines the nature of the ferroelectric distortion.- We measured the magnetoelectric coupling strength in single phase multiferroics by magnetocapacitance measurements. The coupling strength is determined by the quadratic magnetic field dependence of the capacitance. The temperature dependence of the coupling is presented and discussed in terms of a Landau approach. We find that the coupling can be enormously enhanced by chemical substitutions.This work is part of the Ph.D. thesis work of Gwilherm Nénert, Umut Adem, Mufti Nandang, and in collaboration with Agung Nugroho, Graeme Blake, Michael Pollet and Yang Ren.
3:00 PM - T6.2
Control of Ferroelectric Phases by 4f Magnetic Moments in Multiferroic RMnO3 crystals
H. Kuwahara 1 , K. Noda 1 , M. Akaki 1 , F. Nakamura 1 , D. Akahoshi 1
1 Department of Physics, Sophia University, Tokyo Japan
Show AbstractWe report the dielectric and magnetic properties of the perovskite RMnO3 (R=rare earth ions) crystals with and without the presence of the 4f magnetic moments of R ions. The 4f-moment-free compound, (Eu,Y)MnO3, was controlled the average ionic radius of the R site so that it was the same as that of TbMnO3 in which the intriguing magnetoelectric (ME) effect has been recently discovered. The (Eu,Y)MnO3 crystal was found to have two distinct ferroelectric phases with polarization along the a (Pa, T≤23K) and c (Pc, 23K≤T≤25K) axes in the orthorhombic Pbnm setting in a zero magnetic field. In addition, we have demonstrated magnetic-field-induced switching between these ferroelectric phases: Pa changed to Pc by the application of magnetic fields parallel to the a axis (Haext). According to the recent theory, the transversely-modulated spiral antiferromagnetic structure breaks the inversion symmetry and induces ferroelectric polarization through the inverse Dzyaloshinskii-Moriya interaction. The ferroelectric polarization vector is orthogonal to both of the magnetic-modulation wave vector (b axis) and the the vector of magnetic spiral. In the case of (Eu,Y)MnO3, Mn 3d spins rotate in the ab plane and Pa would emerge in a zero field. In the Haext, the field will force the vector of magnetic spiral to the a axis (i.e. the spins rotating in the bc plane), in which Pc would be stabilized. Magnetization measurements supported this interpretation: We confirmed the change of the vector of magnetic spiral from the c axis (the spins rotating in the ab plane) to the a axis (in the bc plane) induced by application of the Haext. Such ME effects are considered to originate from the Mn 3d spins alone, since (Eu,Y)MnO3 is free from the influence of the 4f momentsOn the other hand, in the case of the compounds with the 4f moments (TbMnO3, (Eu,Ho)MnO3), the dielectric and magnetic properties are different from those of the above, although the average ionic radius of R site is the same. The Pc only appears in a zero magnetic field in these compounds. Introducing the 4f moments significantly enhance the magnitude of the magnetization along the a axis compared with the other axes. These results suggest that the internal magnetic field due to the 4f moments seems to be parallel to the a axis (Haint). Such Haint stabilizes the Pc, which is consistent with the case of the Pc in Haext for the 4f-moment-free compound described above. From these results, we conclude that, in RMnO3 crystals, the Mn 3d spins are indispensable for realizing the magnetic-field-induced polarization flop while the 4f moments are not. The magnetic easy axis of the 4f moments determines the ferroelectric polarization vector through the channel of the internal magnetic field. The phase coexistence or switching of Pa and Pc will also be discussed in (Gd,Y)MnO3 crystals.
3:15 PM - **T6.3
Hexagonal Rare-earth Manganite ReMnO3 Grown as Thin Films and Superlattices.
Guillaume Huot 1 , Isabelle Gelard 1 , Bohdan Kundys 2 , Oleg Lebedev 3 , Gustav Van Tendeloo 3 , Catherine Dubourdieu 1
1 LMGP, CNRS/INPG, Grenoble France, 2 CRISMAT, CNRS, Caen France, 3 EMAT, University of Antwerp, Antwerpen Belgium
Show Abstract4:15 PM - T6.4
Multiferroic Behaviors of Ferroelectric Ferromagnet, YbMnO3 Epitaxial Film.
Norifumi Fujimura 1 , Tetsuya Takahashi 1 , Kazuhiro Maeda 1 , Takesh Yoshimura 1
1 School of Applied Materials Science, Osaka Prefecture University, Osaka Japan
Show Abstract4:30 PM - T6.5
Exchange Bias Study of Multiferroic LuMnO3, TbMnO3 and BiFeO3.
Makoto Murakami 1 , S. Fujino 1 , J. Hattrick-Simpers 1 , S. Lofland 2 , Sang-Wook Cheong 3 , D. Kundaliya 4 , S. Ogale 4 , T. Venkatesan 4 , M. Wuttig 1 , I. Takeuchi 1 4
1 Materials Science and Engineering, University of Maryland, College Park, Maryland, United States, 2 Department of Physics and Astronomy, Rowan University, Glassboro, New Jersey, United States, 3 Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey, United States, 4 Center for Superconductivity Research, University of Maryland, College Park, Maryland, United States
Show Abstract4:45 PM - T6.6
Epitaxial Multiferroic Hexagonal YMnO3 and YbMnO3 Thin Films Grown on GaN and ZnO.
Agham Posadas 1 , Jeng-Bang Yau 1 , Charles Ahn 1
1 Applied Physics, Yale University, New Haven, Connecticut, United States
Show Abstract5:00 PM - T6.7
Ferroelectricity and Magnetoelectric Coupling in the Multiferroic Barium Fluorides.
Claude Ederer 1 , Nicola Spaldin 1
1 Materials Department, University of California Santa Barbara, Santa Barbara, California, United States
Show AbstractWe present a first principles study of the series of multiferroic barium fluorides with the composition BaMF4, where M is Mn, Fe, Co, or Ni. We show that the ferroelectricity in these systems results from the "freezing in" of a single unstable polar phonon mode. In contrast to the case of the standard perovskite ferroelectrics, this structural distortion is not accompanied by charge transfer between cations and anions. Thus, the ferroelectric instability in the multiferroic barium fluorides arises solely due to size effects and the special geometrical constraints of the underlying crystal structure. In addition, we show that the ferroelectric distortion gives rise to "weak" magnetic order that can be reversed by reversing the polarization with an electric field. This phenomenon is expected to be very common in magnetic ferroelectrics and can be exploited in the design of magnetoelectric devices.
5:15 PM - T6.8
Toroidal Domain Imaging and Magnetic Structure of LiCoPO4 and LiNiPO4.
Bas Van Aken 1 , Manfred Fiebig 1 2 , Hans Schmid 3 , Jean-Pierre Rivera 3
1 , Max Born Institute, Berlin Germany, 2 HISKP, Universität Bonn, Bonn Germany, 3 Dept. of Chemistry, University of Geneva, Sciences II, 30 Quai E. Ansermet, Geneva Switzerland
Show AbstractLitium orthophosphates LiMPO4 (M=Mn, Fe, Co and Ni) are AFM insulators that exhibit strong linear magnetoelectric (ME) effects, in line with their previously assumed magnetic symmetry mmm'. However, several experiments indicate that the picture is more complicated. (i) Anomalies in the ME effect indicate that the AFM ordering is associated with a 1st order phase transition in LiNiPO4, whereas the other compounds show a 2nd order transition. The 1st order transition is believed to lead to an incommensurate phase, the 2nd order transition to the paramagnetic phase. (ii) For both LiCoPO4 and LiNiPO4 weak FM has been observed with the FM moment parallel to the spin direction. (iii) Neutron diffraction, magnetic annealing and the presence of weak ferromagnetism are not consistent with the mmm' symmetry.
For the point group mmm' and, in particular, with the assumed lower symmetry, ferrotoroidic ordering, i.e., formation of a long-range ordered magnetic vortex state is allowed. This fourth form of ferroic ordering is characterised by simultaneous violation of time-reversal and space-inversion symmetry. Although indications for the presence of toroidal ordering have been reported for other compounds, the acording domain structure, a compulsory property of any form of ferroic order, has not been observed so far.
Optical second harmonic generation has been applied to study the magnetic symmetry and image the domain structures. In both compounds, AFM spin-reversal domains are observed. In addition, in LiCoPO4 ferrotoroidic domains are identified. Analogous with uniaxial ferromagnetically interacting spins, LiCoPO4 allows two, antiparallel orientations of the toroidal moments. Furthermore, the AFM domains in the Co compound have no distinct shape, whereas the AFM domains in the Ni compound are platelets parallel to the spin direction. These weakly ferromagnetic AFM domains can be annealed in a magnetic field. The temperature dependence of the SHG signal, which is absent above TN, reflects the temperature dependence of the ME effect. The SHG intensity of the Co compound decreases continuously to zero when approaching TN, but for LiNiPO4 a step transition at TN is observed. Interestingly, this step transition is moved to lower temperatures with increasing magnetic field. This indicates that the incommensurate phase just above TN is stabilised by the magnetic field. The observation of SHG susceptibilities forbidden for the mmm' point group confirm that the symmetry is lower, presumably being 2'.
In conclusion, a reduced magnetic symmetry has been confirmed for ME LiMPO4 and in LiCoPO4 ferrotoroidic domains have been imaged for the first time which makes the compound a weakly ferromagnetic ferrotoroidic multiferroic.
5:30 PM - T6.9
Magnetic and Electric Phase Control in Epitaxial EuTiO3 from First Principles.
Craig Fennie 1 , Karin Rabe 1
1 Physics and Astronomy, Rutgers University, Piscataway, New Jersey, United States
Show Abstract5:45 PM - T6.10
Magnetoelectric Multiferroism through Cation Ordering in Complex Perovskite Solid Solutions.
R. William McCallum 1 , Vladimir Antropov 2 , Xiaoli Tan 3
1 Mater. & Eng. Phys. Program, Ames Laboratory, Ames, Iowa, United States, 2 Cond. Matter Phys. Program, Ames Laboratory, Ames, Iowa, United States, 3 Mater. Sci. & Eng., Iowa State University, Ames, Iowa, United States
Show AbstractA strategy for developing ferrimagnetism through B-site cation ordering in thermodynamically stable ferroelectric complex perovskites is described, with the aim of realizing both a spontaneous polarization and magnetization at temperatures close to room temperature. Specifically, solid solutions of the complex perovskites Pb(Fe2/3W1/3)O3, Sr(Fe2/3W1/3)O3, and Ba(Fe2/3W1/3)O3 with BiFeO3 are considered. Preliminary data on the 0.75Pb(Fe2/3W1/3)O3–0.25BiFeO3, 0.90Pb(Fe2/3W1/3)O3–0.10Pb(Zn1/2W1/2)O3, and 0.84Pb(Fe2/3W1/3)O3–0.08Pb(Zn1/2W1/2)O3–0.08BiFeO3 ceramics show promising results. The results will be compared to first principles calculations.
T7: Poster Session: Ferroelectrics and Piezoelectrics
Session Chairs
Wednesday AM, November 29, 2006
Exhibition Hall D (Hynes)
9:00 PM - T7.1
Fabrication of Piezoelectric PZT Films Actuator on Thin Metal Plates Prepared by a Hydrothermal Method.
Tuyoshi Aoki 1 , Shigeyoshi Umemiya 1 , Masaharu Hida 1 , Keisuke Sato 1 , Masao Kondo 1 , Kazuaki Kurihara 1
1 , Fujitsu Limited, Atsugi Japan
Show Abstract9:00 PM - T7.10
Structural and Ferroelectric Properties of Ni-substituted Bi4-xNixTi3O12 Thin films by Sol-Gel process
Ricardo Melgarejo 1 , Maharaj Tomar 1 , Luis Angelats 1 , Ram Katiyar 2 , Osbert Oviedo 1
1 Physics, University of Puerto Rico, Mayaguez, Puerto Rico, United States, 2 Physics, University of Puerto Rico, San Juan, Puerto Rico, United States
Show AbstractNickel-substituted Bi4Ti3O12 (i.e., Bi4-xNixTi3O12) were synthesized by sol-gel process for different compositions. Thin films were deposited on Pt (i.e., Pt/TiO2/SiO2/Si) substrate by spin coating. Materials were characterized by x-ray diffraction and Raman spectroscopy. This study indicates that the material makes a solid solution for the compositions: x = 0.00, 0.10, 0.15, 0.20, and 0.30, where a Ni ion replaces the Bi site. The prominent effect of Ni substitution is observed in low-frequency Raman modes. Sol-gel derived thin films of on a Pt substrate and post annealed at 700°C were tested for ferroelectric response which showed high remnant polarization (Pr = 22 µC/cm2 for x = 0.15). The leakage current (less then 10-7 A/cm2) at low field was observed in the film with composition x= 0.15 and 0.20.The polarization of the BNiT (x = 0.15) film decreased to 83% of the initial value after 1x109 switching cycles These results indicate the potential application of Ni substituted bismuth titanate films in non-volatile ferroelectric memories
9:00 PM - T7.11
Improvement of Chemical Bonding States of Bi4-xLaxTi3O12 Thin Films by Post-Annealing and Characterization of interface layer at the Film/Si Substrate.
Atsushi Kohno 1 , Takayuki Tajiri 1
1 Deptartment of Applied Physics, Fukuoka University , Fukuoka Japan
Show AbstractCapacitance-voltage (C-V) characteristics of Au/ sub-100nm-thick Bi4-xLaxT3O12 (BLT) thin films /p-Si (metal-ferroelectric-semiconductor) structures have showed clockwise hysteresis due to ferroelectric nature of BLT as the BLT thin films were crystallized at 550 °C. Although the as-fabricated devices had a large amount of undesirable positive charges in the BLT film and interface states at BLT/Si, they were significantly reduced by post-annealing in O2 at 400 °C. X-ray photoelectron spectroscopy (XPS) showed that the bismuth suboxides were decreased by the post-annealing, indicating that the oxygen vacancies were diminished. After Ar+-sputter etching of the BLT film the Bi suboxide peak increased. However, the suboxides were sufficiently reduced again by the O2 post-annealing. In order to characterize the chemical bonding states of the BLT film near the film/Si interface, the film was thinned by repeating the sputter etching and the post-annealing. As Si2p core-level peaks from the Si substrate and SiOx interface layer became observable, the thickness of the interface layer was evaluated to be ~2.8 nm from the intensity ratio of the Si oxide peaks to nonoxidized Si0 (substrate) peak. We also confirmed that the thickness was not changed by the annealing. It should be noted that the Bi-O bonding state and valence band spectrum near the interface were improved by the annealing. The band gap energy of the interface layer was estimated from the energy loss spectrum of O1s electrons.
9:00 PM - T7.12
Direct Observation of Domain Formation in PbTiO3 Film using in-situ Raman-CVD Combined Equipment.
Ken Nishida 1 , Hiroshi Funakubo 2 , Takashi Katoda 1
1 , Kochi University of Technology, Kochi Japan, 2 , Tokyo Institute of Technology, Yokohama Japan
Show Abstract9:00 PM - T7.14
Materials Integration for Piezoelectric Oxides/Diamond Hybrid Heterostructure MEMS and Characterization
Orlando Auciello 1 , Bernd Kabius 2 , Jon Hiller 2 , Sudarsan Srinivasan 1
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 Center for Electron Microscopy, Argonne National Laboratory, Argonne , Illinois, United States
Show Abstract9:00 PM - T7.15
Single Crystal Mimicking PrScO3 Template on Vicinal SrTiO3 Substrates.
Chad Folkman 1 , Rasmi Das 1 , Chang-Beom Eom 1 , Yanbin Chen 2 , Xiaoqing Pan 2
1 Material Science and Engineering, University of Wisconsin - Madison, Madison, Wisconsin, United States, 2 Material Science and Engineering, University of Michigan - Ann Arbor, Ann Arbor, Michigan, United States
Show Abstract9:00 PM - T7.17
Thickness Dependent Stripe Domains in Thin PbTiO3 Films
Ryota Takahashi 1 , Øystein Dahl 1 , Espen Eberg 1 , Jostein Grepstad 1 , Thomas Tybell 1 2
1 Department of Electronics and Telecommunications, Norwegian University of Science and Technology, Trondheim Norway, 2 NanoLab, Norwegian University of Science and Technology, Trondheim Norway
Show AbstractObservation of stripe domains in thin PbTiO3 films using standard x-ray diffraction at room temperature is discussed. High-quality c-axis oriented thin film samples with thicknesses varying from 6 to 210 unit cells, were grown on buffered NH4-HF etched SrTiO3 and Nb: SrTiO3(001) substrates [1] using off-axis radio frequency magnetron sputtering. Atomic force microscopy revealed atomically flat surfaces with a step and terrace structure of 1 unit cell height. XRD reciprocal space maps around the (103) PbTiO3 and SrTiO3 reflections showed that all samples, including the 210 unit cell thick film were grown coherently on the substrates. High resolution linear Qx scans of the (00l), (103), (303) reflections showed an in-plane aligned superstructure around the specular Bragg peaks, consistent with the presence of ferroelectric stripe domains [2]. For thin samples, the stripe width was found to be proportional to the square root of the film thickness, with domains randomly aligned. The measured intensity of the satellite peaks increased at the same rate as the specular Bragg peak. In contrast, for thicker samples we observed a decrease of the satellite peak intensity. For samples with a film thickness of more than ~100 unit cells, both monodomain films and stripe domains were observed. We interpret this data as evidence for a thickness driven transition from a possible monodomain state to a stripe domain state. In this presentation, we also discuss a relationship between the depolarization field and the observed domain transition [3]. [1] M. Kawasaki et al, Science 266, 1540 (1994)[2] S. K. Streiffer et al, Phys. Rev. Lett. 89, 067601 (2002)[3] B. -K. Lai et al, Phys. Rev. Lett. 96, 137602 (2006)
9:00 PM - T7.19
Doped Strontium Bismuth Tantalate phases adopting the Aurivillius structure.
Karl Whittle 1 , Ian Reaney 1
1 Engineering Materials, University of Sheffield, Sheffield United Kingdom
Show AbstractThin films of SrBi2Ta2O9 are used in non-volatile random access memories due to its high durability to repeated switching of polarisation states. Despite its commercial usage, there are still fundamental questions concerning the relationship between structure and properties, particularly the role of the paraelectric orthorhombic, Amam phase, intermediate between the prototype, I4/mmm and ferrroelectric, A21am phases. In order to study the role of the intermediate phase in electrical properties, a series of samples doped with lanthanide (Ln) ions according to the general formula, SrBi2-xLnxTa2O9 have been fabricated and characterised using X-ray and electron diffraction and Raman spectroscopy. This data has been used to interpret trends in dielectric and ferrroelectric behaviour.
9:00 PM - T7.2
Piezoresponse in Ferroelectric PZT Thin Films.
Dmitry Kiselev 1 , Igor Bdikin 1 , Alena Movchikova 2 , Andrei Kholkin 1 , Gunnar Suchaneck 2 , Gerald Gerlach 2
1 Department of Ceramics and Glass Engineering/CICECO, University of Aveiro, Aveiro Portugal, 2 Institute for Solid State Electronics, Technische Universität Dresden, Dresden Germany
Show Abstract9:00 PM - T7.20
Ferroelectric Nanostructures.
Konstantin Vorotilov 1 , Alexander Sigov 1 , Elena Mishina 1
1 Electronics, MIREA, Moscow Russian Federation
Show Abstract9:00 PM - T7.21
Growth and Characterization of Epitaxial BaTiO3 and SrTiO3 Thin Films on TiN-buffered Si(001) using RF Sputtering.
Chun Wang 1 , Mark Kryder 1
1 Electrical and computer engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
Show AbstractMuch research has been performed to grow epitaxial BaTiO3 (001) and SrTiO3 (001) thin films on Si substrates using a variety of buffer layers. Here we report on the growth of epitaxial thin films of BaTiO3 and SrTiO3 on Si(001) single crystal substrates using a TiN buffer layer with sputtering method. TiN buffer layer was sputtered at 400°C on HF-cleaned Si substrates in Ar environment using compound target. Both SrTiO3 and BaTiO3 with thickness of 40nm were deposited on TiN buffered Si substrates at 500°C. Film crystallinity was evaluated by theta-2theta, phi and omega X-ray diffraction scans. The orientation relationship was determined to be STO(001)[110]||TiN(001)[110]||Si(001)[110]. BaTiO3 has the similar cube-on-cube relation with Si substrates. The full width at half maximum height of TiN(002), SrTiO3(002), BaTiO3(002) peaks were 3, 2 and 1.5 degrees, respectively, obtained from the rocking curves. Atomic Force Microscopy studies showed that the surface roughness of TiN, SrTiO3 and BaTiO3 was 0.4nm, 0.8nm and 0.6nm, respectively. The microstructure of the multilayer was studied using conventional transmission electron microscopy (TEM) and high resolution TEM (HRTEM). The electron diffraction pattern also confirmed the epitaxial relationship between each layer. TEM images showed a smooth and clear interface between Si and TiN, TiN and SrTiO3, TiN and BaTiO3.
9:00 PM - T7.22
Thermal Analysis at Low and High Temperature and Evidence of Structural Transition Induced by Praseodymium in SrTiO3.
Alejandro Duran 1 , Fransisco Morales 2 , Luis Fuentes 3 , Javier Castro 4 , Jesus Siqueiros 1
1 , Centro de Ciencias de la Materia Condensada-UNAM, Ensenada, Baja California, Mexico, 2 , Instituto de Investigaciones en Materiales-UNAM, Mexico, D.F., Mexico, 3 , CIMAV-Chihuahua, Chihuahua, Chihuahua, Mexico, 4 , UACJ-Ciudad Juarez, Ciudad Juarez, Chihuahua, Mexico
Show Abstract9:00 PM - T7.23
MBE growth of BaxSr1-xTiO3 films on SrTiO3, LaAlO3, and MgO substrates
Oleg Maksimov 1 , Patrick Fisher 2 , Hui Du 2 , Paul Salvador 2 , Marek Skowronski 2 , Volker Heydemann 1
1 Electro-Optics Center, Pennsylvania State University, Freeport, Pennsylvania, United States, 2 Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
Show AbstractThere is a wide technological interest in BaxSr1-xTiO3 due to its high dielectric constant and good insulating properties. BaxSr1-xTiO3 films are currently used to develop tunable microwave devices, such as voltage controlled oscillators, tunable filters, and phase shifters. BaxSr1-xTiO3 thin films are usually fabricated by pulsed laser deposition, sputter deposition, metal organic chemical vapor deposition, and spin coating. These techniques often result in polycrystalline, nonstoichiometric, or defective films. Molecular beam epitaxy (MBE) of BaxSr1-xTiO3 is much less studied and only a few reports are available.Here we present MBE growth of BaxSr1-xTiO3 thin films on SrTiO3 (001), LaAlO3 (001), and MgO (001) substrates. Growth is performed both in a conventional MBE system equipped with effusion cells and in a laser-MBE chamber. Films are studied with atomic force microscopy, X-ray diffraction, Rutherford backscattering spectrometry, and transmission electron microscopy. Crystalline quality of the films grown on different substrates as well as with different techniques (MBE and laser-MBE) are compared.This material is based upon work supported by Dr. Colin Wood, ONR under Contract No. N00014-05-1-0238.
9:00 PM - T7.24
Epitaxial Growth and Microstructure of PrScO3 Thin Films on Exact and Four-degree Miscut (001) SrTiO3.
Yanbin Chen 1 , Chad Folkman 2 , Chang-Beom Eom 2 , Xiaoqing Pan 1
1 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Materials Science and Engineering, University of Wisconsin, Madison, Wisconsin, United States
Show Abstract9:00 PM - T7.26
Proton-beam Irradiation Effect in Hydrogen-bonded Ferroelectrics.
Sehun Kim 1 , Byounghoo Oh 1 , Kyu Won Lee 1 , Cheol Eui Lee 1
1 Physics, Korea University, Seoul Korea (the Republic of)
Show AbstractWe have studied the effect of the proton beaqm irradiation on hydrogen-bonded ferroelectrics. The x-ray diffraction pattern revealed a change in the lattice constant along the hydrogen bond directions. The 1H nuclear magnetic resonance showed that the proton irradiation gives rise to a change in the hydrogen mobility. Also, Dielectric measurements indicated a change in the electric dipole moment associated with the hydrogen bond.
9:00 PM - T7.27
Conduction Characteristics of Charge Ordering Type Ferroelectrics,YFe2O4
Ken Imamura 1 , Yoichi Horibe 1 , Takeshi Yoshimura 1 , Norifumi Fujimura 1 , Shigeo Mori 1 , Naoshi Ikeda 2
1 , Osaka Prefecture univ., Sakai , Osaka, Japan, 2 , Okayama univ., Okayama Japan
Show AbstractRFe2O4 family (R=rare earth Dy to Lu and Y) is known as iron mixed valence system and has a crystal structure constructed by an alternate stacking of triangular lattice. In RFe2O4, Fe2+ and Fe3+ ions occupy crystallographically equivalent sites. The competing interaction between iron ions, Fe2+ and Fe3+, lead the charge ordering state on the triangular lattice[1]. Recently, one of our authors, N. Ikeda reported that the ferroelectricity was recognized by the charge ordering in LuFe2O4[2]. In this study, we focused on YFe2O4, which is a member of RFe2O4 family. We performed ac and dc electric measurements to clarify the effect of charge ordering on the electrical conduction properties of YFe2O4. YFe2O4 ceramics were obtained at 1200 οC in oxygen partial pressure PO2 controlled atmosphere by CO-CO2 mixed gas. During sintering, PO2 was controlled at 4.1 × 10-11 atm. The dc resistivity of the YFe2O4 ceramic was measured during heating and cooling between 80K and 300K. The temperature and frequency dependence of reciprocal impedance 1/Z were also measured. As the frequency is increased, the value of 1/Z increases. Moreover, 1/Z is steady in the low temperature region. 1/Z is regardless of the measurement temperature. These features suggest that the conduction mechanism of YFe2O4 is hopping conduction which is not due to thermal activation [3]. [1]N.Ikeda et. al. Ferroelectric,272,309(2002)[2]N.Ikeda et. al. Nature,436,1136(2005)[3]Y.Sakai et. al. JPSJ,55,3181(1986)
9:00 PM - T7.28
Ceramic Processing of 40 wt% Ba0.45 Sr0.55 TiO3/ 60 wt% MgO Ferroelectric Materials.
Parbatee Jagassar 1 2 , Bonnie Gersten 1 2
1 Chemistry, Queens College, CUNY, Flushing, New York, United States, 2 Biochemistry, Queens College, CUNY, Flushing, New York, United States
Show AbstractAlthough, ferroelectric materials such as 40 wt% Ba0.45 Sr0.55 TiO3/ 60 wt% MgO can be utilized as filters, phase shifters, and capacitors, optimal manufacturing processes of these composite materials for bulk materials applications are still being improved so that their properties can be ideal for the applications. These applications make use of the unique properties of the composite such as having a high dielectric constant (ε=80 @RT), low loss tangent (tanδ=0.008 at 10 GHz), and high tunability (26% @ 2V/μm, -20oC). The values of these parameters are dependent on the processing method of this material and their microstructure composition. In this study we compared a slip casting preparation approach to previous studies (i.e., tape casting and dry pressing). The powder characteristics were evaluated with X-ray diffraction (XRD) and dynamic light scattering (DLS) to confirm the initial and final phases and the particle size and distributions. The drying and firing shrinkage were evaluated with a conventional kiln at 1350 and 1450oC. In particular the homogeneity of the microstructure was evaluated using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). It is anticipated that microwave characteristics of the pellets will also be studied.
9:00 PM - T7.29
Evaluation and Modeling of Power Generator with Bimorph PZT Cantilever.
Dongna Shen 1 , Jyoti Ajitsria 2 , Song-Yul Choe 2 , Dong-Joo Kim 1
1 Materials Research and Education Center, Auburn University, Auburn, Alabama, United States, 2 Department of Mechanical Engineering, Auburn University, Auburn, Alabama, United States
Show AbstractThe traditional power source in present wireless remote sensor systems, battery has large volume and requires large amount of maintenance. Therefore, piezoelectric power generator can be a potential alternative to battery, especially enhanced by the miniaturization requirement and low energy consumption of advanced devices as well as the sufficient vibration energy sources and its high conversion efficiency. To utilize piezoelectric cantilevers as energy converter, the device should be designed to operate with high efficiency and simple configuration. PZT (Lead Zirconium Titanate) is a commonly used piezoelectric material for energy conversion because of its large piezoelectric constant and coupling coefficient. In this study, bimorph cantilever generators were designed and fabricated using PZT ceramic benders due to accessible large strain or energy. The parameters influencing the output energy of piezoelectric bimorph cantilevers including the dimensions of the cantilever and the proof mass, the loading ways of the proof mass and the resonant frequency of the cantilever were systematically investigated. The robustness of cantilever structure was also considered for implementing piezoelectric power conversion devices in harsh environments. The final optimal design was realized by considering the balance between the output power and the safety factor through numerical analysis. The energy density generated by the optimized piezoelectric devices was higher than 1 mW at 1-g vibration, which could be enough to operate microsensor systems. To broaden the operation conditions, multiple-resonant frequency device was also explored. In addition, the obtained power from the devices will be compared and discussed with the proposed models.
9:00 PM - T7.3
Evaluation of Pb(Zr,Ti)O3 Diaphragm-Type Film Actuator Prepared by Sputtering and Dry Etching Processes.
Isao Kimura 1 , Shin Kikuchi 1 , Yutaka Nishioka 1 , Yutaka Kokaze 1 , Mitsuhiro Endo 1 , Masahisa Ueda 1 , Tooru Koidesawa 1 , Yasuhiro Morikawa 1 , Koukou Suu 1
1 Instiute for Semiconductor Technologies, ULVAC,Inc., Shizuoka Japan
Show Abstract9:00 PM - T7.30
Evaluation of Fatigue in Seeded and Unseeded PZT Thin Films by Local Piezoelectric Hysteresis Loops
Baoshan Li 1 , Aiying Wu 1 , Paula Vilarinho 1 , Andrei Kholkin 1 , Alexei Gruverman 2
1 , University of Aveiro, Aveiro Portugal, 2 Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractNon-volatile ferroelectric memories use films of PbZrxTi1-xO3 (PZT) and related compositions due to their peculiar electrical properties, such as the switching of the polarization. However, the practical application of these films has been hindered by the ferroelectric fatigue, when the film is sandwiched between Pt metal electrodes. Repeated switching of Pt/PZT/Pt thin film devices resulted in the decrease of the remanent polarization. Several models have been proposed to explain the observed behaviour; however, due the complexity of the fatigue phenomena the exact mechanism is still unclear. PZT thin films with the morphotropic phase boundary composition (52/48) have been prepared on platinized silicon substrates (Pt/Ti/SiO2/Si) using a modified diol-based sol-gel route, by introducing 1-5 mol% of perovskite nano-seeds into the precursor solution. Macroscopic electric properties of seeded films showed a significant improvement of ferroelectric properties, including fatigue. To understand the role of nano-seeds in this behaviour, the systematic study of the local switching polarization during fatigue in unseeded and seeded films was conducted by piezoresponse force microscopy (PFM). It was observed that local PFM loops, which characterize the local domain switching, showed a tendency similar to that of macroscopic hysteresis loops. In addition, it was found that with the addition of the nano-seeds the film grain morphology changed from a columnar type to a granular type structure and affected the domain structure. The observed fatigue behaviour is discussed based on domain wall pinning induced by injected electrons.Aiying Wu, P. M. Vilarinho, A. L. Kholkin, I. M. Miranda Salvado, J. L. Baptista, Integrated Ferroelectrics, 30, 145-154, 2001.
9:00 PM - T7.31
Microfabricated Piezoelectric Cantilevers with Integrated Si Mass for MEMS Power Harvesting Devices.
Jung-Hyun Park 1 , Dongna Shen 1 , Sang H. Yoon 1 , Song-Yul Choe 2 , Dong-Joo Kim 1
1 Material Engineering, Auburn Univerity, Auburn University, Alabama, United States, 2 Department of Mechanical Engineering, Auburn University, Auburn University, Alabama, United States
Show Abstract9:00 PM - T7.33
Chasing a Polar Catastrophe: ab-initio Theory of the LaAlO3/SrTiO3 Interface.
Jaekwang Lee 1 , Alexander Demkov 1
1 Department of Physics, University of Texas-Austin, Austin, Texas, United States
Show Abstract9:00 PM - T7.34
Comparison of Piezoelectric Materials for Vibration Energy Conversion Devices.
Dongna Shen 1 , Song-Yul Choe 2 , Dong-Joo Kim 1
1 Materials Research and Education Center, Auburn University, Auburn, Alabama, United States, 2 Department of Mechanical Engineering, Auburn Unicersity, Auburn, Alabama, United States
Show AbstractPiezoelectric materials have been utilized as vibration energy converters to power wireless devices or MEMS devices due to low power requirement of these devices and the development of miniaturization technology. It has shown the potential that piezoelectric power generator can be an alternative to the traditional power source-battery because of facile vibration sources in our environment and the potential elimination of maintenance required for large volume batteries. To date, PZT (Lead Zirconium Titanate) has been commonly adopted as a piezoelectric material for energy conversion since it can generate higher power density even at low-g (< 1 g) vibration environment. Its high fragility, however, limits its applicability at high-g conditions. One approach to overcome this drawback is to design PZT structure immune from the environmental vibration condition, but such design typically results in lower power conversion. Therefore, other types of piezoelectric materials such as polymer and composite are necessary to investigate the applicability at severe vibration conditions. In this study, PZT-based power generator was examined and optimized by considering the matching frequency with environmental vibration, the generated output power, and maximum g-value without device failure. In addition, polymer piezoelectric material PVDF (Polyvinylidene fluoride) and piezoelectric composite MFC (Macro Fiber Composite)-based cantilevers were also designed and fabricated. The energy conversion of all three types of generators were systematically evaluated and compared with the proposed models. All three devices were measured to generate enough power density for providing electric energy to wireless sensor or MEMS device. The PZT device shows the highest output energy density and PVDF device has the highest durability to operate at high-g vibration condition. The detailed issues on applicability of these devices will be discussed in context with simulated model and fabrication of prototypes.
9:00 PM - T7.35
MxN Electro-Optic Switches Based on Ferroelectric Domain Microengineering.
Mahesh Krishnamurthi 1 , Lili Tian 1 , Venkatraman Gopalan 1
1 Material Science and Engineering and Materials Research Institute, Pennsylvania State University, State College, Pennsylvania, United States
Show AbstractWe present a new class of optical switch based on ferroelectric domain microengineering. The basis of the design is the electro-optic deflection and focusing of a laser beam in ferroelectrics by shaping domains as prisms and lenses, respectively. We demonstrate two types of switches: a 3x3 switch based on optical scanners, and a 1x20 optical switch based on combination of electro-optic lenses and scanners. The performance of the device is simulated by the Beam Propagation Method, and the devices are demonstrated using lithium tantalate single crystal chips.
9:00 PM - T7.36
Local Crystallographic Orientation Imaging in Piezo and Ferroelectric Materials.
Sergei Kalinin 1 , Brian Rodriguez 1 , Stephen Jesse 1 , Edgar Karapetian 2 , Anna Morozovska 3 , Eugene Eliseev 4 , Pradyumna Gupta 5 , Himanshu Jain 5 , David Williams 5
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 Mathematics and Computer Science Department, Suffolk University, Boston, Massachusetts, United States, 3 V. Lashkaryov Institute of Semiconductor Physics, National Academy of Science of Ukraine, Kiev Ukraine, 4 Institute for Problems of Materials Science, National Academy of Science of Ukraine, Kiev Ukraine, 5 Department of Materials Science and Engineering and Center for Optical Technologies, Lehigh University, Bethlehem, Pennsylvania, United States
Show AbstractRapid determination of local crystallographic orientation in nanocrystalline materials is one of the key tasks in nanoscience. Here we develop a framework for local orientation imaging in piezoelectric materials using Piezoresponse Force Microscopy (PFM). We demonstrate that to obtain quantitative molecular orientation data, the measured signal should be (a) related to a rank three tensor property and (b) be independent of SPM probe geometry or easy to calibrate. These criteria limit the possible signals to piezoelectric response and optical second harmonic generation. We show that due to the specificity of voltage dependent contact mechanics, the signal is not sensitive to tip geometry. From the measured electromechanical response vector, local molecular or crystallographic orientation can be reconstructed. A linear theory for the vertical and lateral PFM signals in an anisotropic piezoelectric in terms of the elements of the piezoelectric constants and dielectric anisotropy is developed. The PFM orientational imaging approach is demonstrated on two classes of materials including ferroelectric thin films and PZT ceramics. Crystallographic orientation imaging is demonstrated on a model system of lead titanate ferroelectric thin film using a three dimensional data vector obtained for different sample orientations. The PFM measurements are compared with Electron Back Scattering Diffraction (EBSD) data of the same region. The ubiquitous presence of piezoelectricity in biopolymers and many inorganic materials suggests that Vector PFM has exceptional potential for orientational imaging on the sub-10 nanometer length scale.Research sponsored by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy, under contract DE-AC05-00OR22725 with Oak Ridge National Laboratory, managed and operated by UT-Battelle, LLC.
9:00 PM - T7.37
Peculiar Features of the Dielectric Response in LeadScandium Tantalate Pb(Sc1/2Ta1/2)O3 Thin Films.
Kyle Brinkman 1 2 , Alexander Tagantsev 2 , Vladimir Cherman 2 , Yongli Wang 2 , Nava Setter 2 , Stanislav Kamba 3 , Jan Petzelt 3
1 HDMRG/RIIF, AIST, Tsukuba Japan, 2 Ceramics Laboratory, EPFL, Lausanne Switzerland, 3 Institute of Physics, Academy of Sciences of the Czech Republic, Prague Czech Republic
Show AbstractThe dielectric response of ordered (ferroelectric) and disordered (relaxor) PST thin films were investigated by (i) examining the low temperature (7 K) and high frequency (MHz, GHz and THz) dielectric response where polar region dynamical effects were minimized, and (ii) examining the impact of DC bias fields on the dielectric behavior where large field levels should lead to polar region coalescence. Films in this study were fabricated from a chemical solution deposition method deposited onto single crystal sapphire substrates. The degree of “B” site order was controlled by the annealing conditions: disordered (relaxor) thin films were annealed at 700oC for 20 minutes; while ordered films were annealed at 850oC for 48 hours in a PbO rich atmosphere. Dielectric measurements were performed in the “In-Plane” configuration where the effects of interfacial passive layers are considered to be negligible (Brinkman, Tagantsev, Cherman, Du, Setter, Physical Review B 73, 1 June 2006). The lattice contribution to the dielectric response was determined by using Far Infrared Transmission spectroscopy. At temperatures near the phase transition, ordered films displayed a remarkably high dielectric constant near 7000 resembling their ceramic counterparts. Disordered thin films exhibited frequency dispersion of the dielectric constant characteristic of relaxors, with the magnitude shifted down an order of magnitude (2000 in thin films versus 20,000 in ceramics). An examination of the dielectric permittivity down to 7K revealed significant dispersion between the MHz (dielectric constant~400) and THz (dielectric constant~ 100) frequencies in both disordered and ordered thin films. This difference between the lattice and the response measured in the MHz regime at extremely low temperatures points to the peculiar contribution of polar region/domain wall like objects which maintain their mobility on cooling. Experiments measuring the dielectric constant upon cooling under an electric field reveal an additional peculiar feature of the polar regions in disordered PST thin films: the application of a DC field of 30 kV/cm failed to induce a phase transition to a long range polar state; even at levels 10 times greater than those reported in ceramics. On one hand the nano-domain structure retains its mobility at low temperatures leading to enhanced permittivity, while at the same time refuses to collapse into a macrodomain structure under bias fields as is observed in ceramic relaxors. These results will be discussed in terms of an incomplete transformation to the “relaxor” state in thin films.
9:00 PM - T7.38
Unexpected Growth Modes for Heteroepitaxial BaTiO3 Films Due to Kinetic Limitation.
Junsoo Shin 1 2 , A. Borisevich 2 , S. Kalinin 2 3 , E. Plummer 1 2 3 , A. Baddorf 2 3
1 Physics and Astronomy, University of Tennessee, Knoxville, Tennessee, United States, 2 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 3 Center for Nanophase Materials Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show Abstract9:00 PM - T7.4
Structural and Optical Properties of PbTiO3 Grown on STO Substrate by Peroxide MBE.
Natalia Izyumskaya 1 , V. Avrutin 1 , Xing Gu 1 , U. Ozgur 1 , Tae Dong Kang 2 , Hosun Lee 2 , H. Morkoc 1
1 Department of Electrical and Computer Engineering, Virginia Commonwealth University, Richmond, Virginia, United States, 2 Deptartment of Physics, Kyung Hee University, Yong-In Korea (the Republic of)
Show Abstract9:00 PM - T7.40
Effect of Growth Conditions on Stripe Domains and c-axis Parameter in PTO Ultra-Thin Films.
Rene Meyer 1 , Arturas Vailionis 1 , Paul C. McIntyre 1
1 Materials Science and Engineering, Stanford University, Stanford, California, United States
Show AbstractRecently, a stripe domain structure was discovered in ultra-thin PTO films at elevated temperatures by synchrotron diffraction experiments. These findings are consistent with the presence of ferroelectricity in films even at thicknesses of a few nm [1].We studied the stripe domain periodicity and the dependence of the c-axis lattice parameter on the sample thickness by conventional XRD. Atomically smooth PTO films of 5nm to 50nm thickness were grown by an MOCVD process on insulating STO substrates. Asymmetric diffraction data indicate that the films form a coherent interface with the substrate. We found that the c-axis lattice parameter changes with PTO film thickness, but is even more sensitive to the after-growth cooling conditions. In contrast to earlier studies, stripe domains of different periodicity are observed at room temperature in all samples. The stripe domain periodicity is a function of the film thickness, but also depends on the post- treatment.[1] S.K. Streiffer et al., PRL 89, p. 067601 (2002).
9:00 PM - T7.5
Single-step Sol-gel Deposition of PMNT Thin Films.
Shane O'Brien 1 , Kevin McCarthy 2 , Gabriel Crean 1 3
1 , Tyndall National Institute, Cork Ireland, 2 Dept. of Electrical Engineering, University College Cork, Cork Ireland, 3 Dept. of Microelectronic Engineering, University College Cork, Cork Ireland
Show Abstract9:00 PM - T7.6
Investigation of Epitaxially Grown PbO, TiO2 and ZrO2 as Bridge Layers for Integration of PZT on GaN by MBE.
Xing Gu 1 , Natalia Izyumskaya 1 , Vitaly Avrutin 1 , Hadis Morkoç 1
1 , VCU, Richmond, Virginia, United States
Show Abstract9:00 PM - T7.7
Chemical Solution Derived PZT Thin Films and Fabrication of Flexural Plate Wave Device.
Sang Yoon 1 , Jung-Hyun Park 1 , Dong-Joo Kim 1
1 Materials Engineering, Auburn University, Auburn, Alabama, United States
Show AbstractThe solid solution system of Pb(ZrxTi1-x)O3 (PZT) has been investigated due to high dielectric, electromechanical, and piezoelectric coefficients appropriate for wide range of applications from non-volatile memory to MEMS device. PZT film with morphotropic phase boundary (MPB) composition, Zr:Ti = 52:48 has been studied for a piezoelectric film required in acoustic wave device. Chemical solution deposition (CSD) method was used and optimized for the fabrication of PZT films. Structural characterization of PZT films were performed by X-ray Diffraction, SEM, and Raman Spectroscopy. The modification of process parameters, such as pyrolysis temperature, the presence of chelating agent, and substrate type, was found to control the film microstructure, which eventually affects the piezoelectric properties and device performance. The results showed that low pyrolysis temperature and the chelating agent, acetylacetone, facilitate (111) oriented structure on Pt(111)/Si substrate. The surface morphology and roughness of PZT films were examined by AFM because the morphology can influence the acoustic wave propagation. Under optimized condition, AFM and SEM exhibit dense and uniform structures of PZT films. Dielectric constants above 1000 were obtained and other electrical properties were characterized. PZT-based flexural plate wave (FPW) device has been fabricated onto 4-inch silicon wafer. Properties of PZT-based FPW devices will be discussed in context with potential biosensor applications.
9:00 PM - T7.8
Influence Of Oxygen Vacancies on the Ferroelectric Properties of SBT Doped with Praseodymium
Jorge Mata 1 , Alejandro Duran 1 , Eduardo Martinez 1 , Jesus Heiras 1 , Jesus Siqueiros 1
1 Depto. Propiedades Opticas, Grupo de Ferroelectricos, CCMC-UNAM, Km 107 carretera Tijuana-Ensenada, E-22800. Apdo. Postal 2681., Ensenada, Baja California, Mexico
Show AbstractSrBi2Ta2O9 (SBT) is a ferroelectric material that has attracted much interest, because it is lead-free alternative to PZT for ferroelectric non-volatile memory devices (FeRAM). The introduction of cation vacancies as well as the substitution of rare earth ions (RE) strongly affects the polarization-switching properties of SBT. In this work, we describe the effects of the presence of vacancies in the structure of Sr0.85Pr0.15VxBi2Ti2O9 with x=0, 0025, 0.050, 0.075 and 0.10 (SBT:Pr-V). The literature reports a decrease of the Curie temperature (Tc) and an increase of the permittivity when the Sr-site is replaced either by RE-ions or vacancies. In this study, however, our results show that the introduction of vacancies in SBT:Pr-V produce a considerable decrease in Tc, from 300 to 200 °C, and a remarkable increase of the permittivity around the transition temperature. From the ε-T curves it was observed that the transition temperature depends almost linearly on V content. Broad phase transitions were also observed; this is a typical behavior of ferroelectric materials with diffuse phase transition (DPT). Ferroelectric measurements revealed that Ps is enhanced by Pr-vacancy substitution. The authors would like to thank Pedro Casillas, M. Sainz, J. Peralta and J. Palomares (CCMC-UNAM) for their technical assistance. This work is partially supported by CONACyT Mexico, projects 47714-F and 40604-F and DGAPA-UNAM projects IN116703 and IN100903.
9:00 PM - T7.9
Characterization of Ferroelectric Properties of Bi4−XPrXTi3O12 Polycrystals
Abril Munro 2 1 , Jorge Mata 1 , Eduardo Martinez 1 , Alejandro Duran 1 , Jesus Siqueiros 1
2 Postgrado en Física de Materiales, CICESE-CCMC, Km. 107 Carretera Tijuana-Ensenada. E-22800. Apdo. Postal 2732, Ensenada, Baja California, Mexico, 1 Propiedades Opticas, CCMC-UNAM, Km. 107 Carretera Tijuana-Ensenada. E-22800. Apdo. Postal 2681., Ensenada, Baja California, Mexico
Show AbstractBi4Ti3O12 (BIT) is a perovskite layer structured system and a potential candidate for device application due to its high dielectric constant, high Curie temperature (695oC) and high breakdown strength. It was shown that BIT polycrystals were successfully prepared from nano-sized powders obtained by assisted mechanically synthesis after three hours of milling time. Some structural features such as the phase formation, crystal structure, density and microstructure shows to be influenced by the milling time. Polycrystals of BIT doped with Praseodymium were structurally characterized by X-ray diffraction and by XPS spectroscopy to determine the Pr+3,4 valence state. Measurements of permittivity and polarization show remarkable changes as the Pr ion concentration is increased. A shift toward lower temperatures in the ferroelectric to paraelectric phase transition is attributed to the substitution of Pr3+ for Bi3+ in the BIT structure. We realized the Rietveld refinement technique to investigate the crystal structure of the BIT;Pr samples powders. Acknowledgments: The authors would like to thank P. Casillas, M. Sainz, J. Peralta and J. Palomares for their technical assistance. This work is partially supported by CONACyT México, projects 47714-F and 40604-F and DGAPA-UNAM projects IN116703 and IN100903.
Symposium Organizers
Venkatraman Gopalan The Pennsylvania State University
Jon-Paul Maria North Carolina State University
Manfred Fiebig Max-Born-Institut
Ce-Wen Nan Tsinghua University
T8: Domains and Domain Walls
Session Chairs
Wednesday AM, November 29, 2006
Room 302 (Hynes)
9:30 AM - T8.1
Phase-field Simulations of Ferroelecctric Domain Structres and Domain Switching in Cermaics and Thin Films.
Samrat Choudhury 1 , Yulan Li 1 2 , Long Chen 1
1 Materials Science and Enginnering, The Pennsylvania State University, University Park, Pennsylvania, United States, 2 MPA-STC, MS K763,, Los Alamos National Lab, Los Alamos, New Mexico, United States
Show Abstract9:45 AM - T8.2
Investigation of Twin-Wall Structure at the Nanometer Scale Using Atomic Force Microscopy.
Doron Shilo 1 , Guruswami Ravichandran 2 , Kaushik Bhattacharya 2
1 Department of Mechanical Engineering, Technion - Israel Institute of Technology, Haifa Israel, 2 Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California, United States
Show AbstractThe structure of twin-walls and their interaction with defects has important implications for the behavior of a variety of materials including ferroelectric, ferroelastic, and co-elastic crystals. One unique characteristic of such crystals is that their physical properties as well as their macroscopic response to electrical, mechanical, and optical signals are strongly related to their microstructural domain patterns. These, in turn, are governed by the atomistic and mesoscale structure of twin-walls and their interaction with other crystal defects. For example, it has been shown that as the dimensions of a ferroelectric thin film reduces to the sub-micrometer scale; the twin-wall thickness affects the dielectric, piezoelectric and optical properties of the film. Moreover, as the dimensions further reduce to the nanometer scale, the twin-wall thickness dictates the transitions from a multi-domain structure to single domain and from a ferroelectric to a non-ferroelectric phase.We present a new method for investigating the structure of twin-walls with nanometer-scale resolution. In this method, the surface topography measured using atomic force microscopy is compared with candidate displacement fields, and this allows for the determination of the twin-wall thickness and other structural features. Moreover, analysis of both complete area images and individual line-scan profiles provides essential information about local mechanisms of twin-wall broadening, which cannot be obtained by existing experimental methods. The method is demonstrated in the ferroelectric material lead-titanate and the shape memory alloy CuAlNi. Both materials exhibit twin-wall thickness of few nanometers. Further, it is shown that accumulation of point defects in lead-titanate is responsible for significant broadening of the twin-walls. Such defects are of interest because they contribute to the twin-wall kinetics and hysteresis.
10:00 AM - **T8.3
Luminescence and Raman Based Real Time Imaging of Ferroelectric Domain Walls.
Volkmar Dierolf 1 , C. Sandmann 1 , P. Capek 1
1 Physics, Lehigh University, Bethlehem, Pennsylvania, United States
Show AbstractNovel methods for real-time imaging of ferroelectric domain walls open up new possibilities for advancing physical understanding of domain wall structure, properties, and defect interactions. Instead of destructive chemical etching and subsequent optical or electron microscopy, domain walls are imaged nondestructively in real-time by photoluminescence microscopy using dilute doping by rare earth ions as “designer defects” whose luminescence is affected by the domain walls. Using a combination of high spatial and spectral site-selectvity in laser confocal and near field optical microscopy, Structural changes on a 100 nm length scale can be observed with a temporal resolution of 5ms, as demonstrated in LiNbO3 and LiTaO3. We will demonstrate that the defects are sensitive probes for local electric fields across the domain wall.We will further describe Imaging using Raman spectroscopy (that does not require rare earth doping). Our imaging methods reveal that domain wall widths and structures are velocity-dependent, and they provide active, real time feedback needed for precise laser-writing of ferroelectric domain patterns.
10:30 AM - T8.4
Abnormal Domain Switching Character in PZT Thin Film.
Aiying Wu 1 , Baoshan Li 1 , Paula Vilarinho 1 , Dong Wu 2 , Alexei Gruverman 2
1 Ceramics and Glass Engineering, University of Aveiro, Aveiro Portugal, 2 Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States
Show Abstract10:45 AM - T8.5
Spectroscopic Measurements of Early Stages of Single Domain Switching in Ferroelectric Materials.
Sergei Kalinin 1 , Brian Rodriguez 1 , Stephen Jesse 1 , Anna Morozovska 2 , Eugene Eliseev 3 , Ying-Hao Chu 4 , Tong Zhao 4 , R. Ramesh 4 , Ionela Vrejoiu 5 , Marin Alexe 5
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 V. Lashkaryov Institute of Semiconductor Physics, National Academy of Science of Ukraine, Kiev Ukraine, 3 Institute for Problems of Materials Science, National Academy of Science of Ukraine, Kiev Ukraine, 4 Department of Materials Science and Engineering and Department of Physics, University of California, Berkeley, California, United States, 5 , Max-Planck-Institut für Mikrostrukturphysik, Halle Germany
Show AbstractWednesday 11/29Transferred (poster) T11.8 to (oral) T8.5 9:45 amSpectroscopic Measurements of Early Stages of Single Domain Switching in Ferroelectric Materials. Sergei V. Kalinin
11:30 AM - T8.6
Mutiferroic Domain Dynamics in Strained Strontium Titanate
Aravind Vasudeva Rao 1 , Amit Kumar 1 , Lili Tian 1 , Jeffrey Haeni 1 , Yulan Li 1 2 , Carl-Johan Eklund 4 , Quan Jia 2 , Reinhard Uecker 3 , Peter Reiche 3 , Karin Rabe 4 , Long-Qing Chen 1 , Darrell Schlom 1 , Venkatraman Gopalan 1
1 Materials Science and Engineering, The Pennsylvania State University, University Park, PA, Pennsylvania, United States, 2 MST-STC, Los Alamos National Lab, Los Alamos, New Mexico, United States, 4 Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey, United States, 3 , Institute for Crystal Growth, Berlin Germany
Show AbstractStrontium titanate is normally not a ferroelectric or a multiferroic at any temperature. Multiferroicity can be induced in strontium titanate films by applying biaxial strain, resulting in the coexistence of both ferroelectric and antiferrodistortive domains. The magnitude and sign of the strain imposed on the lattice by design can be used to tune the phase transitions and interactions between these two phenomena. Using optical second harmonic generation, we report a transition from centrosymmetric 4/mmm phase to ferroelectric mm2, followed by an antiferrodistortive transition to a coupled ferroelastic-ferroelectric mm2 phase in a strontium titanate thin film strained in biaxial tension by 0.94%. The results agree well with theoretical first principles and phase-field predictions. Nonlinear optics combined with phase-field modeling is used to show that the dominant multiferroic domain switching mechanism is through coupled 90° ferroelectric-ferroelastic domain wall motion. More broadly, these studies of coexisting ferroelectric (polar) and antiferrodistortive rotation (axial) phenomena are directly relevant to multiferroics with coexisting ferroelectric (polar) and magnetic (axial) phenomena.
11:45 AM - T8.7
Split of In-plane and Out-of-plane Ferroelectric Instabilities in Compressed (001)-epitaxial SrTiO3 film
Tomoaki Yamada 1 , Jan Petzelt 2 , Alexander Tagantsev 1 , S. Denisov 2 , D. Noujini 2 , P. Petrov 3 , A. Mackova 4 , T. Kiguchi 5 , K. Fujito 5 , K. Shinozaki 5 , N. Mizutani 5 , V. Sherman 1 , P. Muralt 1 , N. Setter 1
1 Ceramics Laboratory, Swiss Federal Institute of Technology, EPFL, Lausanne, VD, Switzerland, 2 Institute of Physics, Acad. Sci. Czech Rep., Praha Czech Republic, 3 Centre for Physical Electronics and Materials, London South Bank University, London United Kingdom, 4 Nuclear Physics Institute, Acad. Sci. Czech Rep., Rez near Prague Czech Republic, 5 , Tokyo Institute of Technology, Meguro-ku Japan
Show AbstractIt is well recognized that the mechanical coupling between ferroelectric thin films and their substrates can strongly influence the symmetry of the films and their properties. Haeni et al [1] showed hundreds degrees increase of the Curie-Weiss temperature of strained SrTiO3 (STO), demonstrating a spectacular example of this effect.However, it is less recognized that the film-substrate mechanical coupling will lead to the substantially different in-plane and out-of-plane properties of the film, which brings a qualitatively new effect - a split of the in-plane and out-of-plane ferroelectric instability temperatures. We show here the first observation of such a split by means of infrared (IR) reflection spectroscopy in biaxially strained epitaxial STO thin films.High quality epitaxial 50 nm-thick STO (100) film was deposited on NdGaO3(110) substrate by pulsed laser deposition. The film was strongly in-plane compressed and out-of-plane elongated due to the lattice mismatch between film and substrate. IR reflection spectroscopy revealed the very slow softening of the stiffened in-plane soft mode on cooling. At the same time, another feature, a phonon silent mode, was observed in the spectra below 150 K, corresponding to the appearance of an out-of-plane spontaneous polarization in the film. The observed results point to low in-plane ferroelectric instability temperature (i.e., the extrapolated Curie-Weiss temperature) and high out-of-plane ferroelectric instability temperature in our film [2]. Landau theory analysis of the problem supports these phenomena. The situation corresponds to the prediction of Pertsev et al [3] who theoretically showed that symmetry breaking in cubic paraelectrics can lead to a split of in-plane and out-of-plane ferroelectric instabilities.[1] J. H. Haeni et al., Nature (London) 430, 758 (2004).[2] T. Yamada, et al., Phys. Rev. Lett. 96, 157602 (2006).[3] N. A. Pertsev et al, Phys. Rev. B 61, R825 (2000); 65, 219901(E) (2002).
12:00 PM - T8.8
Environmental Control of Ferroelectricity in Coherently-Strained PbTiO3 Films
Ruey-Ven Wang 1 2 , Brian Stephenson 1 2 , Dillon Fong 2 , Fan Jiang 2 , Stephen Streiffer 1 2 , Paul Fuoss 2 , Jeffrey Eastman 2 , Kujtim Latifi 3 , Carol Thompson 3
1 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States, 2 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 3 Physics Department, Northern Illinois University, DeKalb, Illinois, United States
Show AbstractCompensation of the depolarization field by free charge at interfaces is a determining factor for the ferroelectric phase transition and for domain structures in ferroelectric thin films. Studies [1] of coherently-strained films of PbTiO3 on (001) SrTiO3 have shown that as temperature is lowered from the ferroelectric transition temperature, a sequence of domain structures occurs that reflects changes in charge compensation at interfaces [2]. The stability of monodomain polarization in ultrathin films has been explained by ionic adsorption on the surface [3]. These results indicate that by modifying interface chemistry, we may be able to control ferroelectric domain structure and manipulate ferroelectricity. Here we report on a study of the ferroelectric behavior of PbTiO3 thin films, coherently grown on insulating (001) SrTiO3 or conducting (001) SrRuO3/SrTiO3, that are then equilibrated under different gas environments chosen to manipulate surface chemistry. Utilizing synchrotron x-ray surface scattering, we monitor the evolution of ferroelectric polarization and domain structure in real time as the oxygen partial pressure of the ambient is varied. The sign of the polarization can be reversed by changing between reducing and oxidizing conditions. The surface structures resulting from these conditions are also studied and will be discussed.[1] S. K. Streiffer et al., Phys. Rev. Lett. 89, 067601 (2002)[2] G. B Stephenson & K.R. Elder, to appear in J. Appl. Phys. (2006)[3] D. D. Fong et al., Phys. Rev. Lett. 96, 127601 (2006)
12:15 PM - T8.9
Lead Titanate Films Under Tensile Strain.
B. Noheda 1 , A. Janssens 2 , G. Catalan 1 3 , G. Rispens 1 , A. Vlooswijk 1 , G. Rijnders 2 , D. Blank 2
1 Materials Science Centre, University of Groningen, Groningen Netherlands, 2 MESA+ Institute for Nanotechnology, University of Twente, Enschede Netherlands, 3 Department of Earth Sciences, University of Cambridge, Cambridge United Kingdom
Show AbstractFerroelectric thin films of tetragonal perovskites under tensile strain are particularly interesting since the theory shows that they could display novel phases with low symmetries.1-3 So far little experimental work exists on this type of films due to difficulties during growth and characterization. Mainly, the available perovskite substrates with lattice parameters larger than those of typical ferroelectrics provide too large misfit and, therefore, give place to a too small thickness, if any, before relaxation takes place. Nonetheless, great progress has been attained in the past couple of years: 1) New substrates are available to tune the strain4 and 2) it has been recently shown5 that x-ray grazing incidence diffraction (GID) can expose stripe patterns of polar domains, which are present in ferroelectric thin films as a way to minimize the depolarizing fields, even in films that are three unit cells thick. This provides a new tool to characterize the polar symmetry of fully-strained, very thin films.Stimulated by this success we have grown epitaxial 5 nm thin films of PbTiO3 under 1.1% tensile strain on DyScO3 substrates, using RHEED-assisted Pulsed Laser Deposition. We have performed ex-situ synchrotron x-ray diffraction on those films both in reflection and GID geometry. The films are fully coherent with the substrate and show no 90o domain formation. A mapping of the reciprocal space reveals satellites characterizing an in-plane periodicity of about 30 nm, which is believed to be due to polar stripe domains. The intensity distribution of those satellites shows that the stripes carry in-plane as well as out-of-plane components of the polarization6. Thus, it is shown that, when PbTiO3 is grown under moderate tensile strain, the polarization tilts away from the substrate normal but does not reach a full in-plane configuration. The observed patterns could characterize the so-called ac-phase (in-plane component of polarization along edges), as well as the r-phase (in-plane component of polarization along diagonals) and further work is needed to discriminate between them. The interest of this work is not only fundamental: In these phases, in which the direction of the polarization is not defined by symmetry, the piezoelectric and dielectric responses should be drastically enhanced7,8. Preliminary Piezoresponse Force Microscopy measurements indicate that this may be the case.References: 1 N. A. Pertsev, et al. Phys. Rev. Lett. 80, 1988 (1998).2 C. Bungaro and K. M. Rabe, Phys. Rev. B69, 184101 (2004).3 O. Diéguez et al. Phys. Rev. B 72, 144101 (2005).4 M.D. Biegalski, J. Mat. Res. 20, 952 (2005).5 D. Fong, et al., Science 304, 1650 (2004).6 G. Catalan et al. Phys. Rev. Lett. 96, 127602 (2006).7 L. Bellaiche et al. , Phys. Rev. Lett. 84, 5427 (2000).8 B. Noheda, Current Opinion in Sol. Stat. & Mat. Sc. 6, 27 (2002).
12:30 PM - **T8.10
Stability and Mobility of Charged Ferroelectric Domain Walls.
Alexander Tagantsev 1 , Pavel Mokrý 2
1 IMX Ceramics Laboratory, Swiss Federal Institute of Technology (EPFL), Lausanne Switzerland, 2 Electrical Engineering, Technical University of Liberec, Liberec Czech Republic
Show AbstractCharged domain walls can be present in various ferroelectric systems. It is known that ferroelectric domain walls can bear bound polarization charge as soon as the normal component of the polarization is not continuous across it. The additional electrostatic energy associated with this charge makes the configurations containing such walls energetically less favorable and, under certain conditions, make a charged wall absolutely unstable. However, in practice, the appearance of charged domain walls is often inevitable. This always happens at the reverse domain nucleation during ferroelectric switching. Another situation where charged domain walls are likely to appear takes place when a ferroelectric is poled along a direction which is different from all possible directions of the spontaneous polarization in the crystal. Of practical interest is the case of “oblique” poling of the so-called morphotropic-boundary materials. An important feature of these systems is the possibility of full or partial screening of the bound charge on the wall with free electronic charge available in the material. The present paper theoretically addresses the stability and mobility of charged domain walls, which essentially control the switching and poling phenomena in these systems. The focus of the paper is on the effects associated with the screening of the bound charge on the wall with free charges and the effects associated with the vicinity of the material to a morphotropic boundary. We will demonstrate that these effects can be of crucial importance for the performance of ferroelectric materials.
T9: Nanoscale Ferroic Phenomena, Characterization, and Applications
Session Chairs
Alexei Gruverman
Sergei Kalinin
Wednesday PM, November 29, 2006
Room 302 (Hynes)
2:30 PM - T9.1
Quantitative Piezoresponse Force Microscopy of Ferroelectrics: Experiments and Numerical Simulations
Lili Tian 1 , Venkatraman Gopalan 1
1 Material Science & Engineering Department, Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractPiezoelectric Force Microscopy (PFM) is extensively used today to image ferroelectric domain walls. Ferroelectric domain wall thickness is predicted to be only few lattice parameters wide, though PFM image of the wall is of the order of tens of nanometers. What is the resolution of the PFM technique, and how is it related to the tip shape, tip size, and geometry of tip-sample interaction? In this study, piezoresponse force microscopy (PFM) is used to investigate the local electromechanical response across a single 180° domain wall in ferroelectric crystals such as lithium niobate and lithium tantalate. The interaction domain width and quantitative response of both vertical response and lateral response in PFM versus the tip geometry and tip size are investigated by both experimental approach and the numerical finite element method simulations. It is shown that even for sharp tips, a disk shaped contact area model, with no dielectric gap between tip and sample most closely resembles the actual PFM measurements of resolution and amplitude of response. Excellent agreement between the experiment and numerical analysis is achieved.
2:45 PM - T9.2
Spatial Resolution, Information Limit, and Contrast Transfer in Piezoresponse Force Microscopy.
Sergei Kalinin 1 , Albina Borisevich 1 , Stephen Jesse 1 , Brian Rodriguez 1 , Stephen Pennycook 1 , Anna Morozovska 2 , Eugene Eliseev 3
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 V. Lashkaryov Institute of Semiconductor Physics, National Academy of Science of Ukraine, Kiev Ukraine, 3 Institute for Problems of Materials Science, National Academy of Science of Ukraine, Kiev Ukraine
Show AbstractScanning probe-based domain imaging and ferroelectric domain patterning has attracted broad attention for the characterization of ferroelectric materials, ultrahigh density data storage and nanofabrication. The viability of these applications is limited by the minimal domain size that can be fabricated and detected by scanning probe microscopy (SPM). Here, the contrast transfer mechanism in Piezoresponse Force Microscopy (PFM) of ferroelectric materials is analyzed in detail. We illustrate that in PFM the image can be represented as a linear convolution between the ideal image representing sample properties, and the microscope resolution function. The Fourier transform of the latter, the object transfer function (OTF), describes the transmission between the frequency components of the object and experimental image. For SPMs with a monotonic OTF, two characteristic lengths can be unambiguously defined. The Raleigh two point resolution establishes the conditions necessary for quantitative measurements of local properties and is related to the full width of the OTF at the half maximum. The information limit of the technique determines the minimal feature size that can still be detected, and is determined by the noise level of the system. For PFM, the resolution and information limits are determined from the domain wall profiles and written periodic domain pattern. Experimental determination of the OTF and subsequent reconstruction of the “ideal image”, reflecting the material properties, is demonstrated. The difference between resolution in a PFM mixed signal and phase images is discussed. This contrast transfer theory provides a quantitative basis for image interpretation and the comparison of different instruments in PFM. It is shown that experimentally observed domain sizes can be limited by SPM resolution to the order of tens of nanometers, even though smaller domains can be created. Research sponsored by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy, under contract DE-AC05-00OR22725 with Oak Ridge National Laboratory, managed and operated by UT-Battelle, LLC.
3:00 PM - T9.3
Cross-sectional Observation of Nano-domain Dots Formed in Congruent Single-crystal LiTaO3.
Yasuo Cho 1 , Yasuhiro Daimon 1
1 , R.I.E.C. Tohoku Univ., Sendai Japan
Show AbstractRecently, we have been studying ferroelectric ultrahigh-density data storage and previously reported the successful formation of nanosized inverted domain dot arrays at a data density of 10.1 Tbit/in2 in a congruent LiTaO3 (CLT) single-crystal thin plate. In addition, we have achieved real data recording at an area density of 1 Tbit/in2 with a bit error rate of only 1.8×10-2. [1]However, there are a lot of points to be studied, for example, concerning the mechanism of polarization reversal, the cross-sectional shapes of nano-domain dots formed just below the probe tip and the effects of stress in the domain boundary vicinity. It is very important to elucidate these points experimentally. However, we have been able to obtain information on the sample surface only by conventional scanning nonlinear dielectric microscopy (SNDM) due to the high concentration of the electric field just below the tip.[2] Thus, in the present study, we measured the cross-sectional nano-domain shape by using SNDM, aiming to observe the depth penetration behavior of nano-domain dots. First, the cross-sectional nano-domain shape was revealed by cross-sectional measurements using SNDM, whereby we confirmed that the reversal nano-domain dots penetrated the entire sample. We also confirmed that the SNDM signal obtained from reversal domains became clearer as the sample thickness decreased. Next, we evaluated the domain wall thickness from each measurement result by curve fitting. It was found that thinner samples have a tendency to have thinner domain walls. Moreover, we confirmed that the domain wall thickness at the bottom of the sample was thinner than the front surface of the sample. This information will be applied to discuss the stability of inverted domain dots.[1]Y. Cho, S. Hashimoto, N. Odagawa, K. Tanaka and Y. Hiranaga: Appl. Phys. Lett. 87, (2005) 232907[2]Y. Cho and K. Ohara: Appl. Phys. Lett. 79, (2001) 3842
3:15 PM - T9.4
Ferroelectric Domain Imaging and Polarization Switching in Strained SrTiO3 Films using Piezoelectric Force Microscopy
Amit Kumar 1 , Lili Tian 1 , Aravind Rao 1 , Michael Biegalski 1 , Yulan Li 2 , Long-Qing Chen 1 , Darrell Schlom 1 , Venkatraman Gopalan 1
1 Materials Science and Engineering, Pennsylvania, University Park, Pennsylvania, United States, 2 , Los Alamos National Labs, Los Alamos, New Mexico, United States
Show AbstractAlthough bulk strontium titanate is not a ferroelectric at any temperature, epitaxially grown strained thin films of SrTiO3 on (110) orthorhombic DyScO3 and GdScO3 substrate films exhibit ferroelectric behavior. No report of direct ferroelectric domain imaging has been reported in this material so far. The ferroelectric polarization in a 0.94% strained SrTiO3 on DyScO3 is along the <110>p directions. We have directly imaged the ferroelectric domains in this film using Piezoelectric Force Microscopy from 296-333K across the phase transition. The domain walls are parallel to the <100>p direction of SrTiO3 (where the subscript p indicates pseudocubic notation) indicating 90-degree domain walls. By applying external fields and performing in situ piezoelectric force microscopy, the mechanism of ferroelectric polarization switching is demonstrated to be motion of 90 degree domain walls, in agreement with phase field modeling. The relaxor behavior of the ferroelectricity is confirmed by the disappearance of PFM signal at 323K (Tb) which is higher than the temperature at which peak in the dielectric constant appears (250K, Tmax). Ferroelectric domains in SrTiO3 films on GdScO3 substrate are influenced by anisotropic in-plane strains, which affect the polarization orientation and switching dynamics.
3:30 PM - T9.5
Microstructure of Epitaxial BiFeO3 Thin Films Grown on Exactly and Four-degree Miscut (001) SrTiO3 Substrates.
Xiaoqing Pan 1 , Yanbin Chen 1 , R. Das 2 , D. Kim 2 , Chang-Beom Eom 2
1 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Materials Science and Engineering, University of Wisconsin, Madison, Wisconsin, United States
Show AbstractIn recent years, considerable interest has been focused on multiferroic materials that show ferroelectric and ferromagnetic properties simultaneously. BiFeO3 is one of typical multiferroic materials. In this paper, epitaxial BiFeO3 thin films with a SrRuO3 bottom electrode were fabricated by sputtering on both exact and vicinal (001) SrTiO3 substrate. The microstructures and ferroelectric domain configurations of the films were studied by transmission electron microscopy (TEM). Electron diffraction patterns taken along three different crystallographic directions show that BiFeO3 films have the rhombohedral structure. The ferroelectric domain structures of the BiFeO3 films were determined by electron diffraction and dark field imaging. The atomic structures of film/substrate interfaces and ferroelectric domain walls were characterized by HRTEM. It was also found that atomic steps on the SrTiO3 substrate have a strong effect on the BiFeO3 domain structure and ferroelectric properties. Furthermore, the ferroelectric domain structures of BiFeO3 films with different thicknesses were studied.
4:15 PM - T9.6
Domain Structure and Polarization of Ferroelectric Graded Multilayers and Films
Alexander Roytburd 1
1 , University of Maryland, College Park, Maryland, United States
Show AbstractWednesday, 11/29Transferred from Poster to OralT7.39 to T9.6 at 3:15 pmDomain Structure and Polarization of Ferroelectric Graded Multilayers and Films. A. Roytburd
4:30 PM - T9.7
Piezoresponse Force Microscopy in a Liquid Environment:Ultrahigh Resolution, Tip-Surface Interactions, and Cantilever Dynamics.
Brian Rodriguez 1 , Stephen Jesse 1 , Sergei Kalinin 1
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractRecent improvements in piezoresponse force microscopy (PFM) sensitivity have allowed a wide variety of weakly piezoelectric materials such as III-nitride thin films and biopolymers in calcified and connective tissues to be investigated with up to 10 nm resolution. However, in order to probe electroactive soft condensed matter systems and perform high-resolution studies of ferroelectric perovskites, one needs a fundamentally a different approach to PFM that minimizes both the electrostatic interactions and the tip-surface forces. To improve the resolution and sensitivity of this technique, we have adapted PFM to a liquid environment. Resolution on the order of 3 nm, approaching the theoretical domain wall width, as compared to a resolution of ~30 nm in ambient, is reported on model ferroelectric ceramics. The dynamic behavior of the cantilever was analyzed using conventional amplitude-frequency and 2D amplitude-frequency-bias spectroscopy. It is shown that the viscous damping and added mass effects can be reduced by high frequency operation, which minimizes the volume of liquid excited by the cantilever. The amplitude-frequency-bias spectroscopy illustrates a complete absence of dc electrostatic forces in liquid. The observed high resolution is attributed to screening by mobile ions in liquid and an absence of capillary interactions, as confirmed by imaging in NaCl solutions of varying concentrations. This results in the localization of the ac field to the tip-surface junction. Interpretation of electromechanical interactions in solution requires that capacitive interactions and coupling in the double layer must be taken into account. The future potential of Liquid PFM for high resolution probing of ferroelectric materials and effect liquid has on polarization switching and domain patterning are discussed.Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory (ORNL), managed by UT-Battelle, LLC for the U. S. Department of Energy under Contract No. DE-AC05-00OR22725.
4:45 PM - T9.8
Simultaneous Observation of Surface Morphology and Dielectric Properties Using Non-Contact Scanning Nonlinear Dielectric Microscopy with Atomic Resolution.
Ryusuke Hirose 1 , Yasuo Cho 1
1 Research Institute of Electrical Communication, Tohoku University, Sendai Japan
Show Abstract Scanning Nonlinear Dielectric Microscopy (SNDM) has been developed as the technique for observing the local dielectric properties of material surface. Especially this technique has been known as the powerful tool for the ferroelectric polarization characterization. This microscopy can measure the higher order nonlinear dielectric constants ε(4) and ε(5) as well as the lowest order nonlinear dielectric constant ε(3) which contains the polarization information [1]. Recently, we have developed Non-Contact Scanning Nonlinear Dielectric Microscopy (NC-SNDM) with a new height-control technique utilizing higher order nonlinear dielectric constant detection (ε(4) signal)[2]. In theoretically, NC-SNDM has quite high height sensitivity against the gap between tip and sample as well as STM technique and the simultaneous observation of the topography and ferroelectric polarization (local dipole moment) distribution with atomic resolution has been expected. To confirm such performance of SNDM with atomic resolution, UHV-SNDM was developed. In this study, Si(111) cleaned surface by heat treatment was chosen as a specimen. As a result, we have succeeded in observing Si(111) 7x7 atomic structure. Moreover, distribution of tunnelling current and lowest order nonlinear dielectric signal ε(3) could be observed simultaneously. To the best our knowledge, this is the first successful demonstration of the atomic resolution achievement in dielectric microscopy techniques. Thus, SNDM can be recognized as the fifth microscopy technique with atomic resolution as well as Field Ion Microscopy (FIM), Transmission Electron Microscopy (TEM), Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM). Besides, it is expected that NC-SNDM will be a powerful technique for the observation of surface topography and dielectric properties on ferroelectric materials as well as semiconductors with atomic resolution.[1] Y. Cho and K. Ohara, Appl. Phys. Lett., 79 (2001) 3842.[2] K. Ohara and Y. Cho, Nanotechnology, 16 (2005) S54.
5:00 PM - T9.9
Characterization of Polarization Switching of FeRAM Capacitor using a Multi Probe AFM.
Nobuhiro Kin 1 2 , Kazuaki Takai 2 , Koichiro Honda 1 2
1 , Fujitsu Laboratories LTD., Atsugi Japan, 2 , Fujitsu Limited, Kawasaki Japan
Show Abstract To develop higher density FeRAM requires reducing the cell size. However, as the capacitor size reduces, it becomes more difficult to measure the ferroelectric characteristics of the FeRAM capacitor. It has therefore become important to analyze the electrical characteristics of the single-bit cell capacitor. We have developed a new method of analyzing memory devices by adopting a technique that uses multi-probe AFM as a tool to overcome the single-probe limitation in AFM. There can be five probes in this system. Fast square pulses with a rise time in the order of nanoseconds are used to obtain the switchable polarization of the FeRAM single-bit cell capacitor. Two separate probes contact the TEC and BEC individually to apply the fast pulse. For this study, we used sputtered 200-nm thick polycrystalline (111) lead zirconium titanate (PbZr0.4Ti0.6)O3 thin films with IrO2 top electrodes, and Pt bottom electrodes. The films were deposited on Si/SiO2/Ti substrates with 2.0 um2 capacitors. A tungsten probe whose top radius is about 15 nm was used for the measurements. The contact angle to the surface is narrower than usual for AFM probes. The spring constant of a tungsten probe is about 100 [N/m], hard enough to maintain stable contact with the electrode. The results are summarized here:(1) We reduced the parasitic capacitance to 1/10 that of the conventional AFM measurement system. (2) High-speed pulse measurements with a 50-nanosec pulse width have been achieved in an actual FeRAM single-bit cell capacitor.(3) Characterizing the ferroelectric properties, it is often said that the write time tends to be somewhat long, especially in imprint capacitors. Since the pulse speed is faster in this multi-probe AFM system than with the conventional method, this phenomenon can be recognized. Therefore, this multi-probe AFM system is well-positioned to become a standard industry tool for device testing, just like high-speed pulse measurements.
5:15 PM - T9.10
Nanoscale Patterning and Characterization of Multifunctional Oxides.
Zixiao Pan 1 , Vinayak Dravid 1
1 Materials Science and Engineering, Northwestern University, Evanston, Illinois, United States
Show AbstractOrdered low-dimensional multifunctional oxides such as ferroelectrics and multiferroics have attracted considerable attention due to their potential device applications in diverse fields. These materials exhibit one or more significant order parameters such as polarization, magnetization, and elastic strain, among many others. The corresponding properties show remarkable size dependency as well as interesting coupling when different materials are positioned in close proximity. Therefore, the ability to manipulate these materials at nanometer length scales and control the dimension, morphology and internal structure of the nanostructures are prerequisite to study their novel properties at varied length scales, and to realize useful miniaturized devices through such synergistic coupling. We have recently introduced the "soft electron beam lithography" (soft-eBL) approach as a novel combination of electron beam lithography and wet chemistry for site-specific fabrication of functional oxides nanostructures. [1] This approach circumvents the traditional etching process in ceramic patterning and has shown great versatility in structural control of the obtained nanopatterns. [2] The presentation will cover the soft-eBL strategy for nanopatterning of ferroelectric and multiferroic oxides. Specifically, we will demonstrate fabrication of radially stacked ferroelectric/magnetic composite heterostructures in a facile two-step procedure. This approach avoids painstaking feature-realignment for nanoscale integrating hierarchical architectures and may prove valuable for fabricating all-oxide heterostructures with novel functionalities. We will further introduce soft-eBL fabrication and localized characterization of single phase ferroelectric (BaTiO3) and multiferroic (BiFeO3) nanostructures, and emphasize the versatility of soft-eBL in control of the morphology and internal structure of nanopatterns. Particularly, below a certain pattern size, the as-patterned amorphous BaTiO3 nanodiscs can be readily converted into dense, single-crystal form that exhibit heteroepitaxy with respect to the underlying SrRuO3/SrTiO3 substrate. These structures are highly favorable to explore and harness the functionalities at the nanoscale.[1] Donthu, S. et al., Nano Lett., 5, 1710 (2005)[2] Pan, Z. et al., Small, 2, 274 (2006)
5:30 PM - T9.11
Metal-Ferroelectic-Insulator-Semiconductor (MFIS) Structures with Ferroelectric Polymer Nanomesa Arrays
Timothy Reece 1 , Stephen Ducharme 1 , Jihee Kim 1
1 Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska, United States
Show AbstractDemand for improved nonvolatile memories has been growing as many more electronic products become smaller and more powerful. Nonvolatile memories based on ferroelectric thin films have attracted much attention recently because of the lower writing voltage and faster switching speed than those of flash memory. The ferroelectric field effect transistor (FeFET) type memory has a number of specific advantages, including nondestructive readout and a scalable single-device structure. Among the ferroelectric thin films used in FeFET devices; the ferroelectric copolymer of polvinylidene fluoride, PVDF (C2H2F2), with trifluoroethylene, TrFE (C2HF3), has distinct advantages, including low dielectric constant, low processing temperature and good chemical stability. However, due to its relatively large coercive field (> 50 MV/m) and spontaneous polarization (~10 μC/cm2), it is difficult to achieve low voltage operation with ferroelectric polymers. Recently, the fabrication of self-assembled ferroelectric nanomesas, approximately 10 nm thick and 100 nm in diameter, from Langmuir Blodgett films of 70/30 PVDF/TrFE has been a promising development [1]. We discuss the challenges involved in making metal-ferroelectric-insulator-semiconductor structures incorporating these nanomesas, as well as their effects on device performance. This work is supported by the National Science Foundation.1.M. Bai, S. Ducharme, Appl. Phys. Lett. 85, 3528-30 (2004).
5:45 PM - T9.12
Ultraviolet Raman Spectroscopy of Nanoscale Ferroelectric Heterostructures.
Dmitri Tenne 1 , Xiaoxing Xi 1 2 , Arsen Soukiassian 2 , Wei Tian 2 , Darrell Schlom 2 , Axel Bruchhausen 3 , Alejandro Fainstein 3 , Ram Katiyar 4 , Andres Cantarero 5 , Yulan Li 2 8 , Long-Qing Chen 2 , Quanxi Jia 8 , Kyoung-Jin Choi 6 , Chang Beom Eom 6 , Haiping Sun 7 , Xiaoqing Pan 7 , Serge Nakhmanson 9 , Karin Rabe 9
1 Physics, The Pennsylvania State University, University Park, Pennsylvania, United States, 2 Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States, 3 , Centro Atomico Bariloche & Instituto Balseiro, San Carlos de Bariloche Argentina, 4 Physics, University of Puerto Rico, San Juan, Puerto Rico, United States, 5 Materials Science Institute, University of Valencia, Valencia Spain, 8 Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 6 Materials Science and Engineering, University of Wisconsin, Madison, Wisconsin, United States, 7 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 9 Physics and Astronomy, Rutgers University, Piscataway, New Jersey, United States
Show AbstractT10: Poster Session: Dielectrics
Session Chairs
Thursday AM, November 30, 2006
Exhibition Hall D (Hynes)
9:00 PM - T10.1
Preparation and Dielectric Properties of Nb2O5-BaO-Na2O-SiO2 Glass-ceramic.
Mao Changhui 1 , Sun Xudong 1 , Du Jun 1 , Yang Zhimin 1
1 Advanced electronic material division, General Research Institue for Non-ferrous Metals, Beijing China
Show AbstractIn this paper, full density Nb2O5-BaO-Na2O-SiO2 Glass-ceramics, which could be used as the dielectric energy-storage materials in fabricating high energy density devices, were prepared by means of rapid quenching and succeeding annealing under different temperature. DTA and X-ray diffraction analysis show that NaNbO3 with perovskite structure and NaBa2Nb5O15 with tungsten bronze structure are formed as the dielectric phases from the glass at 680~720°C. Dielectric constant of the as-annealed Glass-ceramics were measured at the frequency from 10Hz to 100KHz under the testing temperature from 25~140°C, the results indicate that i) Dielectric constant increases with the increase of annealing temperature, ii) the difference of the dielectric constant is less than 10% at the frequency range from 100Hz to 100KHz, iii) Dielectric constant increases slightly with the increase of temperature from 25 to 140 °C. Further research by high-resolution transmission electron microscope (HRTEM) and breakdown strength testing show the full density and low defects contamination structures of the Nb2O5-BaO-Na2O-SiO2 Glass-ceramics, which result in the increase of the breakdown strength, would be benefit to improve the energy-storage density of the materials.
9:00 PM - T10.10
Dielectric Properties of Highly Oriented Pb(Sc0.5Nb0.25Ta0.25)O3 Thin Films.
Margarita Correa 1 , Pijush Battacharya 1 , Ram Katiyar 1
1 Physics, University of Puerto Rico, San Juan, Puerto Rico, United States
Show Abstract9:00 PM - T10.11
Dielectric Permittivity Mapping up to 9GHz Region with Non-contact Microwave Probe for ferroelectric Material and Device
Hirofumi Kakemoto 1 , Jianyong Li 1 , Takakiyo Harigai 1 , Song-Min Nam 1 , Satoshi Wada 1 , Takaaki Tsurumi 1
1 , Tokyo Institute of Technology, Meguro, Tokyo, Japan
Show AbstractRecently, dielectric devices, such as multi-layer ceramic capacitor (MLCC) prepared by BaTiO3 (BT) based material (X7R property) have been miniaturized and used at high frequency. The high frequency dielectric measurement technique for microscopic region is useful for the designing and preparation of these dielectric devices. In experimental, the microwave reflection (r) intensity measurement using scanning non-contact state probe was carried out for measuring the dielectric distribution in the ferroelectric material and device. The dielectric measurement using non-resonant and contact probe was setup with an oscillator inserted a Gunn diode, directional coupler, detector (diode), coaxial tube and probe (6mmφ). The measurement frequency was changed from 9GHz to 11GHz using an oscillator. The r intensity was measured at room temperature as a function of distance between sample and probe. The sample was selected for BT single crystal and MLCC (cross-section). The reverse surface of BT was deposited Au films. In order to observe the microscopic dielectric distribution, analysis and adjustment of spatial resolution were carried out for microwave probe. The spatial resolution was calculated using Bethe’s theory based on Kirchihoff’s diffraction theory. As the result, distance dependence of r intensity was shown the minimum value caused from transmission to the reverse surface with a part of absorption in the sample. The r intensity at minimum value was transformed to dielectric permittivity. The r intensity mapping was also carried out at r intensity minimum position. From r intensity mapping, dielectric permittivity distribution of MLCC and BT was investigated in measurement frequencies.
9:00 PM - T10.12
Dielectric Properties of Cr2O3 Doped (Ba,Sr,Ca)TiO3 Ceramics for Tunable Microwave Devices
Bing Qin 1 , Dengren Jin 1 , Jinrong Cheng 1 , Zhongyan Meng 1
1 materials science , Shanghai University, Shanghai China
Show Abstract9:00 PM - T10.13
Dielectric Properties of Fe-doped Ba0.6Sr0.4TiO3 Thin Films grown by Pulsed Laser Deposition
Jia Gong 1 , Jinrong Cheng 1 , Weicheng Zhu 1 , Shengwen Yu 1 , Zhongyan Meng 1
1 , Shanghai University, Sahnghai China
Show Abstract9:00 PM - T10.14
Dielectric Tunability Properties and Thermal Stability of (Ba,Sr,Ca)TiO3 Thin Films Prepared by the Sol-gel Method
Wei Qin 1 , Wenbiao Wu 1 , Jinrong Cheng 1 , Zhongyan Meng 1
1 , Shanghai University, Sahnghai China
Show Abstract9:00 PM - T10.15
Dielectric Spectroscopy of Pulsed Laser Deposited Lead Zirconate Titanate and Cobalt Iron Oxide Composite Thin Films.
Nora Ortega 1 , S. Majumder 2 , P. Bathacharya 1 , R. Katiyar 1 , P. Dutta 3 , M. Seehra 3
1 Physics, University of Puerto Rico, San Juan, Puerto Rico, United States, 2 materials Science Center, Indian Institute of technology, Kharagpur India, 3 Physics, West Virginia University , Morgantown, West Virginia, United States
Show AbstractMagnetoelectric materials, which exhibit simultaneous magnetic and ferroelectric ordering and with coupling between the two properties, are now a days being studied extensively for a variety of device applications. As compared to single-phase materials the magnetoelectric effect is reported to be more pronounced in piezoelectric-ferromagnetic bulk composite and thin films. In case of thin film composites it has been experimentally observed as well as theoretically predicted that ferromagnetic columns, epitaxially grown in piezo/ferroelectric matrix (1-3 composites) exhibit large magnetic induced electric polarization responses (MIEP). Compared to the 1-3 composites the MIEP response in lamellar (2-2 type) type composite is predicted to be significally low. The weak magnetic effect is reported to be due to clamping effect of the substrate that inhibits the in plane piezo-deformation in such structures. From the studies it appears that the distribution of ferromagnetic phase in piezoelectric matrix plays an important role obtain high magnetoelectric coefficient. In the presents work we prepared 2-2 type composites thin films by pulsed laser deposition. Upon rapid thermal annealing, as envisaged from cross sectional SEM as well as XPS depth profile analyses, the layered structures are no longer maintained and PZT-CFO are phase separated to yield 0-3 type composite thin films. For alternate deposited PbZr0.53Ti0.47O3-CoFe2O4 (PZT-CFO) multilayered film (350 nm thick, 3 PZT layer 90 nm each, and 2 CFO layer 40 nm each), rapid thermal annealing at 650 °C for 150 s, dielectric constant, remanent polarization, and remanent magnetization at room temperature were measured to be 560 (at 100 KHz), 18 μC/cm2 (at 12V), and 26 emu/cm3 (55 KOe) respectively. These films also exhibit a temperature independent dielectric constant over a wide temperature range. Impedance spectroscopy analyses were performed to electrically model, the system as insulating PZT matrix and semiconducting CFO regions with different relaxation times. The observed dielectric relaxation has been explained by Maxwell-Wagner type contributions at the interface between insulating PZT and semi-insulating CFO regions
9:00 PM - T10.16
High Nonlinear Dielectric Properties of Ferroelectric Bilayers and Multilayer Heterostructures.
Shan Zhong 1 , S. Pamir Alpay 1 , Alexander Roytburd 2 , Joseph Mantese 3
1 Chemical, Materials & Biomolecular Engineering, University of Connecticut, Storrs, Connecticut, United States, 2 Materials Science and Engineering, University of Maryland, College Park, Maryland, United States, 3 , Delphi Research Laboratories, Shelby Township, Michigan, United States
Show Abstract9:00 PM - T10.17
Rayleigh Analysis of Ferroelectrics.
Ichiro Fujii 1 , Eunki Hong 1 , Susan Trolier-McKinstry 1 , Craig Nies 2 , Michael Muir 2
1 Materials Research Institute and Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States, 2 Advanced Products and Technology Center, AVX Corporation, Myrtle Beach, South Carolina, United States
Show Abstract9:00 PM - T10.18
Study of the Insulator-Metal Phase Transition in Thin Film Vanadium Oxide (VO2).
Ramesh Mani 1 2 , Shriram Ramanathan 1 2 , Venkatesh Narayanamurti 1 2
1 Gordon McKay Laboratory, Harvard University, Cambridge, Massachusetts, United States, 2 Division of Engineering and Applied Sciences , Harvard University, Cambridge, Massachusetts, United States
Show AbstractThe VO2 phase of Vanadium Oxide undergoes a structural monoclinic- to tetragonal- phase transition in the vicinity of 68 0C. This structural transition produces a band- realignment and an insulator-to-metal transition with increasing temperature, which brings with it orders-of-magnitude changes in the electrical resistance, in addition to significant changes in the infrared optical transmission. These observed changes in the electrical and optical properties in the vicinity of room temperature have created interest in applying this material in novel electrical and optical switching applications, and they have also motivated studies that aim to realize control over the electronic transition, independent of the structural transition.We have synthesized thin films of VO2 by electron beam evaporation of VO2 pellets, onto R-plane sapphire. VO2 films were deposited onto photolithograpically patterned rectangular windows on the Al2O3 substrates. After liftoff, contact-pad-windows were patterned by lithography. Then, Cr/Au was thermally evaporated and this was followed by metal liftoff. The contact fabrication was completed by a slow thermal anneal of the specimen at 450 0C for 5 minutes. VO2 device size was varied from 200 x 400 micrometers down to 50 x 12.5 micrometers. The vanadium oxide films were characterized in detail using x-ray diffraction and Rutherford backscattering techniques.We report temperature dependent two-terminal transport studies of these specimens between 20 0C and 100 0C, which exhibit electrical evidence for a structural transition with increasing temperature. Typically, these films exhibit a 1 to 2 orders-of-magnitude drop in the resistance in the vicinity of 68 0C. In addition, the strip resistance generally scales as expected with size, suggesting good contact formation. The measurements also show hysteresis in the temperature dependence of the resistance, which is perhaps suggestive of structural bi-stability in the vicinity of the transition temperature, in addition to a memory effect in the measured resistance, which reflects the number of thermal cycles through the structural phase transition. Finally, I-V characteristics show that the initial linearity in the I-V curve is followed by nonlinearity due to heating at the highest bias. These and other results help to characterize the properties of VO2 films produced by e-beam evaporation, which constitutes an elegant approach to realizing devices from this technologically important material.
9:00 PM - T10.19
Bonding, Termination and Band Alignments at Metal –Metal Oxide Interfaces.
John Robertson 1 , Koon-yiu Tse 1
1 Engineering, Cambridge University, Cambridge United Kingdom
Show Abstract9:00 PM - T10.2
Dielectric Properties of (Ba,Sr)TiO3 Thin Films Prepared by Chemical Solution Deposition.
Macit Ozenbas 1 , Umut Adem 1
1 Metallurgical and Materials Engineering, Middle East Technical University, Ankara Turkey
Show AbstractIn this study, barium strontium titanate (BST) thin films with different compositions (Ba0.9Sr0.1TiO3, Ba0.8Sr0.2TiO3, Ba0.7Sr0.3TiO3, Ba0.5Sr0.5TiO3) were prepared by chemical solution deposition technique. Crack free films in the thickness range 400-600 nm’s were produced. The effects of heat treatment schedule, thickness of the films and Sr content of the films on the microstructure were correlated to measured electrical properties. It was observed that dielectric constant increased but dielectric loss also increased with increasing thickness and sintering temperature, and the highest dielectric constant was that of Ba0.7Sr0.3TiO3 film. BST films have composition dependent Curie temperature. For Ba content greater than 70 %, the material is in ferroelectric state. However, fine grain size of the films associated with chemical solution deposition and Sr doping causes the suppression of ferroelectric behaviour in BST films. Therefore, only for Ba0.9Sr0.1TiO3 composition, slim hysteresis loops with very low remanent polarization values were obtained.
9:00 PM - T10.20
The Reconstructive Crystal Structure and the Exchange Energy.
Ahmad Yazdani 1 , R. Osaty Araghi 2 , F. Arya 3
1 Physics, Tarbiat Modarres University, Tehran Iran (the Islamic Republic of), 2 , Tarbiat Nodares University, Tehran Iran (the Islamic Republic of), 3 , Tarbiat Nodares University, Tehran Iran (the Islamic Republic of)
Show Abstract9:00 PM - T10.3
Temperature Dependence of Dielectric Properties of BaTiO3/SrTiO3 Artificial Superlattices.
Takakiyo Harigai 1 , Hiroyuki Kimbara 1 , Hirofumi Kakemoto 1 , Satoshi Wada 1 , Takaaki Tsurumi 1
1 , Tokyo Institute of Technology, Tokyo Japan
Show AbstractArtificial superlattices, which multi-layered structures consist of two different lattice constants, have the potential to drastically improve material properties or to show unknown functionalities. In hetero-structured artificial superlattices, large lattice distortion could be introduced in the in-plane direction by the stacking layers. So, material properties of artificial superlattice might be controlled artificially. BaTiO3/SrTiO3 artificial superlattices were fabricated on SrTiO3 single crystal substrates by the molecular beam epitaxy process. X-ray diffraction (XRD) reciprocal space mappings were performed using high-resolution XRD. In all artificial superlattices, the superlattice with the 10-periodic structure showed the clear satellite peaks in the XRD pattern and was mostly distorted in the direction of film thickness. The complex admittance of the superlattices with interdigital electrode was measured by a network analyzer at frequencies up to 1 GHz. The dielectric permittivity was determined from the complex admittance using electromagnetic field analysis. The permittivity of the superlattices was changed as a function of the period of layers and the highest permittivity was obtained for the 10-periodic structures. The temperature dependence of dielectric properties was measured in the range from -50 to +150 degrees at 1 GHz. Compared with BaxSr1-xTiO3 solid solution samples, there was almost no temperature dependence of dielectric permittivity of the artificial superlattices around room temperature. The origin of the high dielectric permittivity has not been clearly understood at present, the anisotropic lattice distortion played an important role to determine the dielectric properties of artificial superlattices.
9:00 PM - T10.4
Dielectric Permittivity Enhancement in PZT by Light Doping with Gd.
Jesus Siqueiros 1 , Jorge Portelles 2 1 , Nelson Almodovar 2 1 , Oscar Raymond 1 , Eduardo Martínez 1 , Jesús Heiras 1 , Juan Fuentes 2
1 Centro de Ciencias de la Materia Condensada, Universidad Nacional Autónoma de México, Ensenada, Baja California, Mexico, 2 Facultad de Física, Universidad de La Habana-IMRE, La Habana, La Habana, Cuba
Show AbstractDoping with small amounts of Gd enhances the maximum permittivity (εmax) of PZT by an order of magnitude. PbZr0.53Ti0.47O3 (PZT 53/47) doped with 0.6% at. of Gd2O3 has been produced following the traditional solid state reaction technique. The ferro-paraelectric transition temperature is reduced from 386 °C to 352 °C. The average crystallite size was found to be 43 nm, a value comparable with those obtained by long time milling mechanical alloying and larger concentrations of Gd2O3. Remnant polarization and coercive field measurements were made from the hysteresis loops obtained at 23 °C and at different applied electric fields up to a maximum of 15 kV/cm. Piezoelectric performance was studied in the 4 Hz to 4 MHz frequency range at 25 °C and the radial electromechanical coupling factor was determined. A detailed electrical conductivity study in the 30-450 °C temperature range is performed in a wide frequency interval to determine the influence of Gd doping. The different participating transport mechanisms are elucidated and the corresponding activation energies were determined by fitting the experimental data. In particular, in the 30 to 300 °C temperature interval, the ac conductivity fallows Jonscher universal relaxation law. This work was partially supported by DGAPA-UNAM Proj. No. IN100903, IN109305-3, and CoNaCyT Proj. No. 47714-F and 40604-F. Thanks are due to V. García, I. Gradilla, P. Casillas, E. Aparicio for technical help.
9:00 PM - T10.5
Effect of Raw Material Characteristics on Microstructure and Dielectric Properties of SrTiO3 Ceramics.
Zhaohui Wu 1 , Hongtao Yu 1 , Hanxing Liu 1
1 , Wuhan University of Technology, Wuhan China
Show Abstract9:00 PM - T10.6
Effect of CuO on Microstructure and Microwave Dielectric Properties of CaTiO3-Ca(Zn1/3Nb2/3)O3 Ceramics System.
Hongtao Yu 1 , Zhaohui Wu 1 , Hanxing Liu 1
1 , Wuhan University of Technology, Wuhan China
Show Abstract9:00 PM - T10.7
Preparation and Characterization of Ba0.6Sr0.4TiO3 Thin Films Prepared on LaNiO3 Buffered Titanium
Weicheng Zhu 1 , Jinrong Cheng 1 , Shengwen Yu 1 , Zhongyan Meng 1
1 , Shanghai University, Sahnghai China
Show Abstract9:00 PM - T10.8
Phase Transition and Dielectric Properties of Ta Substituted Ba6Ti2Nb8O30 with Tungsten-Bronze Structure.
Jeong-Ryeol Kim 1 , Dong-Wan Kim 2 , In-Sun Cho 1 , Chin-Moo Cho 1 , Kug-Sun Hong 1
1 School of Materials and Science Engineering, Seoul National University, Seoul Korea (the Republic of), 2 Materials Science & Engineering Division, Korea Institute of Science and Technology, Seoul Korea (the Republic of)
Show AbstractThe crystal structure and dielectric properties of Ta substituted Ba6Ti2Nb8O30 ceramics were investigated as well as the behavior and features of the ferroelectric phase transition using X-ray powder diffraction and an impedance analyzer. The Ta substitution for Nb ions decreased the ‘c’ lattice parameter which can affect (001) polar axis in the tetragonal tungsten bronze structure, while that increased the ‘a’ lattice parameter. The apparent Curie temperature (Tm) determined from the maximum of the relative dielectric constant had a linear relation with the axial ratio c/a. The Tm of Ba6Ti2Nb8O30 and Ba6Ti2(Nb0.6Ta0.4)8O30 was 55oC and -60oC at 1 MHz, respectively. Ba6Ti2Nb8O30 ceramics had a weak ferroelectricity (2Pr ~ 0.8 μC/cm2), but Ba6Ti2(Nb0.6Ta0.4)8O30 ceramics had a paraelectricity at room temperature. These dielectric and ferroelectric properties were discussed with the ferroelectric phase transition and the disordered distributions of BO6 octahedron.
9:00 PM - T10.9
Interfaces in Barium Titanate Films on Nickel Substrates
Tanawadee Dechakupt 1 , Susan Trolier-McKinstry 1
1 Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractThe evolution of an interfacial layer between BaTiO3 thin films and nickel electrodes was non-destructively investigated by spectroscopic ellipsometry (SE). In this work, BaTiO3 films were deposited on nickel foils by chemical solution deposition. Typically, the deposited films were subjected to a standard heat treatment process (dry, pyrolysis, pre-crystallization, crystallization and re-oxidation). After a 1000°C anneal, the optical constants of the crystallized BaTiO3 film agree well with reference data from a ceramic sample, suggesting good film density. SE revealed a 400 Å thick NiO layer between BaTiO3 and Ni foil after re-oxidation. The AFM surface roughness and XPS depth profiles agree well with SE results. The BaTiO3 film with the NiO layer shows a dielectric constant of ~1000 and loss tangent of 0.025 at 10 kHz. By tracking each heat treatment step, it was found that the NiO thickness remains constant after pre-crystallization (750oC, flowing N2), crystallization (1000oC, pO2 10-16) and re-oxidation (600oC, pO2 10-6). Thus, the crystallization and re-oxidation conditions do not induce additional nickel oxidation. Similarly, the films pre-crystallized at different temperatures between 600-750oC showed approximately the same NiO thicknesses. Therefore, the study concentrated on the oxidation of nickel induced during the drying and pyrolysis steps. Results on the optimization of the organic removal steps to minimize Ni oxidation will be reported.
T11: Poster Session: Nanoscale Phenomena, Characterization, and Applications
Session Chairs
Thursday AM, November 30, 2006
Exhibition Hall D (Hynes)
9:00 PM - T11.1
Nanodomain Size Distribution in Relaxor Ferroelectrics Determined from Temperature Dependent Raman Scattering.
Sanju Gupta 1
1 Physics and Materials Science, Missouri State University, Springfield, Missouri, United States
Show AbstractRelaxors (PZN, in particular) is an important class of self-assembled nanostructure composite ferroelectric oxides (or perovskite) materials. The interesting features associated with the nanoregions/nanodomains required to describe these relaxors give rise to the most relevant device related characteristics and peculiar properties in these materials. In addition, they possess astronomical property coefficients by themselves or when modified with lead titanate (PT) forming solid solution. In the past we conducted temperature dependent Raman scattering studies on solid solution (1-x)PZN-xPT relaxors single crystals with carrying composition; x = 0.02, 0.085, and 0.11 under optical and electric-field variables [1]. While former variable refers to the polarization (both parallel and perpendicular), the latter is the crystallographic direction. These studies were performed to obtain relevant information about lattice/phonon dynamics for matching the application criteria such as actuators. We showed that the sharp structural phase transition at or near 460 K is a first-order transition by fitting two spectroscopic variables in Raman spectra for one of the representative bands occurring at 277 cm-1. Besides structural phase transition, polarization mechanism for the unpoled (x = 0.02) and poled (x = 0.05) specimens is also been investigated to understand the polarization mechanism in relaxors using Raman spectroscopy. The difference in the case of poled specimen is accounted for by the influence of residual electric field. Poling also suggested an enhanced local ordering and the increase in the volume of the polar nano-regions. In the present report, we will discuss the bi-nomial or Weibull distribution for the nano-domains present in these inhomogeneous materials which help to determine the size distribution of nanoscopic embodiments using Raman spectroscopy as a function of temperature which is a dynamical phenomenon. *Supported by internal funds. [1] Gupta et. al. J. Raman Spectroscopy 33 (2001).
9:00 PM - T11.10
Polarization Control Type FET with a Ferroelectric Gate and a Polar Semiconductor.
Norifumi Fujimura 1 , Takeshi Yoshimura 1 , Ryota Arai 1
1 School of Applied Materials Science, Osaka Prefecture University, Osaka Japan
Show Abstract9:00 PM - T11.11
Ferroresistive Memories.
Rene Meyer 1 , Paul C. McIntyre 1
1 Materials Science and Engineering, Stanford University, Stanford, California, United States
Show AbstractOver the last decades, a variety of resistive non-volatile memory concepts have been proposed based on the ferroelectric effect. Prominent examples of ferroresistive memories are ferroelectric diodes, ferroelectric tunneling junctions and ferroelectric multilayer structures. A combination of ferroelectric information storage and resistive read-out is highly desired, since it combines switching speed, low voltage operation and cycling endurance of today’s FeRAMs with the scaling advantages of resistive memories. Even though resistance switching was experimentally confirmed for this kind of devices, the memory effect may not necessarily originate from changes in the ferroelectric polarization state. Resistance switching has also been observed for a number of binary and complex dielectric oxides which do not exhibit ferroelectric switching.This contribution discusses the relationship between ferroelectric polarization and conduction. We studied the influence of internal polarization screening by mobile charge carriers and the depolarizing field on the I-V hysteresis of a ferroresistive device. A metal-ferroelectric-semiconductor-metal structure is chosen as a model structure. Calculations of a 1-dimensional and a 2-dimensional model involving the formation of 180° domains are compared to experimental data. We will show that the reduction of the effective polarization by the depolarizing field has a significant impact on the shape of the I-V curve, which allows one to distinguish between ferroelectric and non-ferroelectric switching. Results may contribute to the fundamental understanding of conduction phenomena in ferroelectrics and are expected to provide design rules for improving the performance of potential ferroresistive memories.
9:00 PM - T11.13
Modulation of Metal-Insulator Transition in Strained Vanadium Dioxides Thin Films.
Takeshi Yanagida 1 , Kazuki Nagashima 1 , Hidekazu Tanaka 1 , Tomoji Kawai 1
1 ISIR-Sanken, Osaka University, Osaka Japan
Show Abstract9:00 PM - T11.14
Synthesis of Nanorods of Alkali Earth Titanates by Alkalide Reduction.
Olivera Zivkovic 1 , Michael Wagner 1
1 Chemistry, The George Washington University, Washington, District of Columbia, United States
Show AbstractFor more than a decade there has been a great interest in the synthesis of nanomaterials due to their unusual size dependent properties that can be superior to their bulk counterparts in catalytic, magnetic and electronic applications. However, there are not many synthetic procedures for ternary and more complex nanomaterials, much less ones that would at the same time, allow their shape control.Alkalide reduction is a powerfulmethod for synthesis of compositionally complex materials. Here we report its application to the synthesis of series of alkali earth titanates MTiO3 (M=Mg, Ca, Sr, Ba). Alkali earth titanates are important dielectric materials that adopt perovskite structure. They are widely used as materials for capacitors, thermistors and switches. BaTiO3 and Ba/SrTiO3 are ferroelectric and as such are utilized in fabrication of sensors, micro actuators and nonvolatile memory devices.Synthesis (production) of nanoscale alkali earth titanates w/ shape control has been achieved by co reduction of Ti4+ and M2+with alkalide solution followed by annealing of the product. Variation in the annealing procedure allows the production of either nanoparticles (3-5 nm in diameter) or nanorods (~500 nm long, 20-30 nm diameter).
9:00 PM - T11.15
Growth of Epitaxial Thin Films of the Ordered Double Perovskite La2NiMnO6 on Different Substrates and Under Different Oxygen Pressures.
Haizhong Guo 1 , Arunav Gupta 1 , James Burgess 1 , Earl Ada 1 , Shane Street 1 , Thomas Calvarese 2 , Mas Subramanian 2
1 , Center for Materials for Information Technology and Department of Chemistry, University of Alabama, Tuscaloosa, Alabama, United States, 2 , DuPont Central Research and Development, Experimental Station, Wilmington, Delaware, United States
Show Abstract9:00 PM - T11.16
Preparation of Pb1-xLax(Zr1-yTiy)1-x/4O3 Thin Films by Sol-gel Method and Their Characterization.
Burkan Kaplan 1 , Macit Ozenbas 1
1 Metallurgical and Materials Engineering, Middle East Technical University, Ankara Turkey
Show AbstractIn this study, La3+ was substituted into lead zirconate titanate (PZT) system by Pb1-xLax (ZryTi1-y)1-x/4O3 nominal stochiometry and it was processed via chemical solution deposition on (111)-Pt/Ti/SiO2/Si-(100) substrates. A systematic study was carried out in different regions of PLZT phase diagram to obtain optimized results of ferroelectric, dielectric and optical properties of the material. The effects of sintering temperature and lanthanum modifications were investigated with regard to phase development, microstructure, and ferroelectric and dielectric characteristics. For the microstructure characterization, effect of La and temperature on grain size were investigated. The electrical and optical properties such as hysteresis curves, dielectric constant, dielectric loss and optical transmittance of the films were obtained. For the tetragonal region, maximum dielectric constant was reached at 10 %La content as 287. The optical constants of the Pb0.91La0.09(Zr0.65Ti0.35)0.9775O3 thin film was obtained from the transmission spectra and with the help of the modified envelope method.
9:00 PM - T11.17
Growth of High Quality Pb(ZrxTi1-x)O3 Films by Peroxide MBE and their Optical and Structural Characteristics.
V. Avrutin 1 , Natalia Izyumskaya 1 , Xing Gu 1 , U. Ozgur 1 , Bo Xiao 1 , Tae Dong Kang 2 , Hosun Lee 2 , H. Morkoc 1
1 Department of Electrical and Computer Engineering , Virginia Commonwealth University, Richmond, Virginia, United States, 2 Deptartment of Physics, Kyung Hee University, Yong-In Korea (the Republic of)
Show Abstract9:00 PM - T11.18
Raman Spectroscopy of Pulsed Laser Deposited La2/3Ca1/3MnO3 Films Grown on Different (110) Oriented Substrates.
Ratnakar Palai 1 , R. Katiyar 1 , R. Chakalova 2
1 Department of Physics, University of Puerto Rico, San Juan, Puerto Rico, United States, 2 School of physics & Astronomy, The University of Birmingham, Birmingham, B15 2TT United Kingdom
Show Abstract9:00 PM - T11.19
Patterning Oxides towards the Nanoscale by Stencil Deposition
Paul te Riele 1 , Arjen Janssens 1 , Guus Rijnders 1 , Dave Blank 1
1 Inorganic Material Science, MESA+ Institute for Nanotechnology and Faculty of Science & Technology, University of Twente, Enschede Netherlands
Show AbstractIn recent years progress is made in characterizing oxides with sub-micron and even nanoscale features. However, structuring these materials to these dimensions has always been quite a challenge. The chemical stability and high deposition temperatures of these oxides often make the use of conventional structuring techniques impossible. Therefore a high throughput technique like stencil deposition combined with pulsed laser deposition is investigated to structure these materials by local deposition.During a stencil deposition, a perforated silicon nitride membrane is placed in front of the substrate. The plasma only propagates through the apertures in the stencil resulting in copy of the structures in the stencil. Due to the high temperature stability of the stencil, the substrate can be heated up to 800 degrees Celsius enabling crystalline growth of complex oxides. Applying this technique under these conditions it is possible to grow these materials in the right structural phase with an epitaxial relation to the substrate. With every stencil deposition, a gap between stencil and substrate is present. Broadening of the structures is therefore inevitable and caused by several mechanisms, such as surface diffusion and geometric broadening. At high deposition pressures (~0.1 mbar, typical for the deposition of oxides), the formation of a shock-wave causes extensive broadening and limits the successful growth of structures with sharp edges. Because of these limiting mechanisms it is quite a challenge to push this technique towards the nano-regime. Another application of this technique is making use of the ability to tune the kinetic energy of the arriving species for the deposition of electrodes on fragile surfaces without damaging the surface. This contribution will focus on the broadening mechanisms, how to avoid or to make use of these effects, and the possibility to grow nano-structured functional complex oxides. Focus will be on the structured growth of ferroelectric lead zirconate titanate based oxides with strontium ruthenate electrodes as well as the properties of the resulting all-oxide ferroelectric devices.
9:00 PM - T11.2
Investigation of Local Switching Processes in Pb(ZrxTi1-x)O3 Films by Piezoresponse Force Microscopy.
Igor Bdikin 1 , Andrei Kholkin 1 , Seung-Hyun Kim 2
1 Department of Ceramic and Glass Engineering, CICECO, University of Aveiro, Aveiro Portugal, 2 , Inostek Inc., Ansam Technopark 707, Snagrok, Ansan, Korea (the Republic of)
Show Abstract9:00 PM - T11.20
Solution Phase Synthesis of Perovskite Nanoparticles
Byron Gates 1 , Bryan Wood 1
1 Chemistry, Simon Fraser University, Burnaby , British Columbia, Canada
Show Abstract9:00 PM - T11.21
Long Term Retention Characteristic of Small Inverted Dots Formed on Congruent Single-Crystal LiTaO3.
Yasuo Cho 1 , Nozomi Odagawa 1
1 , R.I.E.C. Tohoku Univ., Sendai Japan
Show AbstractWith the advance of information processing technology, high-density and high-capacity data storage have been required. However, the storage density of magnetic storage, which plays a major role in this field, will reach a physical limit in the near future. Therefore, an alternative high-density data storage system is required. We have been studying about ferroelectric data storage based on scanning nonlinear dielectric microscopy (SNDM) as a read-and-write device. We have already achieved storage density of more than 10Tbit/inch2 with inverted domain dot array formed on congruent single-crystal LiTaO3(CLT) thin plate. [1] Another required characteristic for the realization of ferroelectric data storage is long-term-retention characteristic. This means data with inverted domain array on ferroelectric medium must remain for long term. In the actual memory device, much longer term data retention characteristic over 10 years is required. Therefore, in this study, we have investigated retention characteristics of nano domain dot formed on ferroelectric data storage medium. To investigate long term retention characteristic of data with inverted domain dots formed on CLT, we conducted heat treatment test. The reason is as follows; the free energy of ferroelectric material has two local minimum points. There is energy barrier between two local minimum points and the system requires high energy enough to surpass the energy barrier when data with inverted domain dots erase by switching back of domain. To accelerate switching back of domain, we left CLT specimen with inverted-domain-dot array in very high temperature atmosphere and compared the shape of the inverted domain dots before and after the heat treatment. After we obtained the result of heat treatment test in 4 temperatures (300degC, 280degC, 250degC and 220degC), we evaluated that the value of activation energy and frequency factor of Arrhenius equation.Using these parameters, we got shrinking speed of inverted dot radius as a function of temperature. Calculated shrinking speed of inverted dot radius in 80degC which is the maximum temperature at use condition in general memory devices is 6.74×10-5nm/h and it means that it takes 16.9 years until inverted dot array with the radius of 50nm loses its radius down to 40nm. This retention characteristic is good enough for comparing with lifetime period 10 years of general memory devices because reading inverted dot array by SNDM is absolutely able even if dot radius of 50nm gets 40nm.[1]Y. Cho, S. Hashimoto, N. Odagawa, K. Tanaka and Y. Hiranaga: Appl. Phys. Lett. 87, (2005) 232907
9:00 PM - T11.22
Synthesis of Nanoscale Metal-oxides under Photon Irradiation and their Integration with High-mobility Semiconductors.
Chia-Lin Chang 1 , Shriram Ramanathan 1
1 DEAS, Harvard University, Cambridge, Massachusetts, United States
Show AbstractMulti-functional oxides are being actively researched for their relevance to applications in varied nanoelectronic and spintronic devices including advanced transistors, spin tunnel junctions and ferroelectrics. Synthesis of nanoscale oxides of precisely controlled structures and stoichiometry is therefore important to understand fundamental properties of complex oxide nanostructures. An elegant approach towards synthesis of nanoscale oxides at low temperatures is by oxidation of precursor metal films, particularly in presence of radiation such as ultra-violet light. In this paper, we present our recent research results on understanding the fundamental effects of irradiation during growth of nanoscale oxides. We present a detailed theoretical and experimental study of ultra-violet (UV) light enhanced low temperature nanoscale metal oxidation. The theoretical model includes elementary processes due to oxygen adsorption and desorption at the oxide/gas interface; ionic currents within the growing oxides enhanced by the UV-induced high-field migration; and electronic tunnel current in the metal-oxide-oxygen systems. In addition, this model is utilized to calculate the self limiting thickness for oxide formation with and without UV irradiation including the effect of oxygen partial pressure for the first time. Our numerical results indicate trends consistent with published experimental data. We also present electrical properties of nanoscale oxides such as CeO2, Y-doped zirconia prepared by the above technique and evaluate their performance by fabricating representative metal-oxide-semiconductor device structures using high-mobility semiconductor substrates such as Ge and InAs. Further, results from physical characterization techniques such as high-resolution ion scattering will be presented to correlate electrical results to the structure and composition.The role of ultra-violet radiation in controlling oxygen stoichiometry in complex oxide systems will be discussed in detail.
9:00 PM - T11.23
The Complex Interplay Between Grain Boundaries and Ferroelectric Domains in Polycrystalline Ferroelectric Thin Films.
Nagarajan Valanoor 1 , Anbusathaiah Varatharajan 1
1 School of Materials Science, University of New South Wales, Sydney, New South Wales, Australia
Show Abstract9:00 PM - T11.3
Piezoresponse Force Microscopy Study of Domain Structure of (Pb1-xLax)(Zr0.65Ti0.35)O3 Ceramics.
Dmitry Kiselev 1 , Igor Bdikin 1 , Karlis Bormanis 2 , Andrei Kholkin 1
1 Department of Ceramics and Glass Engineering/CICECO, University of Aveiro, Aveiro Portugal, 2 Institute of Solid State Physics, University of Latvia, Riga Latvia
Show Abstract9:00 PM - T11.4
Frequency-Modulation Piezoresponse Force Microscopy: Piezoresponse Detection Based on Resonance Tracking Ultrasonic Atomic Force Microscopy.
Hirotake Okino 1 4 , Kei Kobayashi 2 , Hirofumi Yamada 3 , Kazumi Matsushige 3 , Enrico Colla 4 , Nava Setter 4 , Takashi Yamamoto 1
1 Dept. of Communications Eng., National Defense Academy, Yokosuka, Kanagawa, Japan, 4 Ceramics Laboratory, Swiss Federal Institute of Technology-EPFL, Lausanne, Baud, Switzerland, 2 International Innovation Center, Kyoto University, Kyoto, Kyoto, Japan, 3 Dept. of Electronic Sci. and Eng., Kyoto University, Kyoto, Kyoto, Japan
Show Abstract9:00 PM - T11.5
Capacitor Size Effect on Domain Switching Dynamics in Thin Film Ferroelectric Capacitors
Dong Wu 1 , Alexei Gruverman 1 , Brian Rodriguez 2
1 , North Carolina State University, Raleigh, North Carolina, United States, 2 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractAn experimental approach for quantitative measurements of the polarization reversal mechanism in thin film PZT ferroelectric capacitors based on piezoresponse force microscopy (PFM) in conjunction with a pulse switching system is presented. Instant domain configurations developing in the 1x1.5 μm^2, 3x3 μm^2 and 5x5 μm^2 capacitors at different stages of the polarization reversal process have been detected by PFM. Along with the domain structure imaging the switching current signal is measured. Integration of the switching current signal provides information on the time dependence of the switching charge that is compared with the domain switching dynamics measured by PFM. It is shown that the polarization reversal process is characterized by two distinctive stages: the fast one which proceeds mainly via nucleation mechanism and the slow one where the predominant mechanism is lateral domain growth. The fraction of the capacitor switched via the different mechanisms is field-dependent with the contribution of the nucleation mechanism increasing with the field strength. From comparison of the domain dynamics and switching current it is shown that the slow switching stage is not detected by the current measurements. It is also found that the capacitor switching behavior is spatially inhomogeneous – capacitor regions along the electrode edge mainly switch via the lateral domain wall motion while the switching in the central regions is dominated by nucleation. This effect is further manifested in the capacitor size effect on switching behavior - with the decrease in the capacitor size the contribution of the nucleation mechanism is diminished due to the reduced square/perimeter ratio. These findings dictate the necessity of developing a new approach for describing the switching behavior in the thin film capacitors.
9:00 PM - T11.6
A Novel Scanning Magnetic Probe Microscope Utilizing Bulk Multiferroic Laminates.
Jason Hattrick-Simpers 1 , Liyang Dai 1 , Manfred Wuttig 1 , Ichiro Takeuchi 1
1 Materials Engineering, University of Maryland, College Park, Maryland, United States
Show Abstract9:00 PM - T11.7
Local Probing of Polarization Switching in Low-dimensional Ferroelectrics.
Stephen Jesse 1 , Brian Rodriguez 1 , Sergei Kalinin 1 , Eugene Eliseev 2 , Anna Morozovska 3 , Ionela Vrejoiu 4 , Marin Alexe 4
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 Institute for Problems of Materials Science, National Academy of Science of Ukraine, Kiev Ukraine, 3 V. Lashkaryov Institute of Semiconductor Physics, National Academy of Science of Ukraine, Kiev Ukraine, 4 , Max-Planck-Institut für Mikrostrukturphysik, Halle Germany
Show Abstract
Symposium Organizers
Venkatraman Gopalan The Pennsylvania State University
Jon-Paul Maria North Carolina State University
Manfred Fiebig Max-Born-Institut
Ce-Wen Nan Tsinghua University
T12: Dielectrics, Ferroelectrics and Piezoelectrics
Session Chairs
Thursday AM, November 30, 2006
Room 302 (Hynes)
9:30 AM - T12.1
Detailed Study of Infrared Active Modes by hyper-Raman Spectroscopy in the Relaxor System Pb(Mg1/3Nb2/3)1-x Tix O3 (PMN-xPT) with x=0, 0.27, 0.4, and 1.0 in a Temperature Range of 300 to 900 K.
Holger Hellwig 1 , Alp Sehirlioglu 1 , David Payne 1 , Pengdi Han 1
1 Geology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show Abstract9:45 AM - T12.2
Studies on Doping and Solid-Solution in Sodium Potassium Niobate Based Piezoelectrics Using a Precursor Coating Method.
Huidong Li 1 , Wan Shih 1 , Wei-Heng Shih 1
1 Materials Science & Engineering, Drexel University, Philadelphia, Pennsylvania, United States
Show Abstract10:00 AM - T12.3
Brillouin and Raman Scattering Studies on the Relaxor Ferroelectric 0.71Pb(Ni1/3Nb2/3)O3-0.29PbTiO3 Single Crystal.
Tsukada Shinya 1 , Ike Yuji 1 , Kano Jun 1 , Wang Ruiping 2 , Shimojo Yoshiro 2 , Sekiya Tadashi 2 , Kojima Seiji 1
1 Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan, 2 , AIST, Tsukuba, Ibraki, Japan
Show Abstract10:15 AM - **T12.4
Study of SrTiO3 Gate Dielectrics.
Tseung-Yuen Tseng 1 2
1 Department of Electronics Engineering, National Chiao Tung University, Hsinchu 300 Taiwan, 2 Department of Materials & Mineral Resources Engineering, National Taipei University of Technology, Taipei 106 Taiwan
Show AbstractAmong various possible candidates of high-k gate dielectrics, SrTiO3 plays an important role because it has high dielectric constant and it can be epitaxially grown on silicon substrate. The fabrication process and properties of SrTiO3 gate dielectrics are reported. The effect of the addition of SiO2 on the microstructure and electrical properties of SrTiO3 gate dielectrics is also presented. The minimization of the effect of interfacial layer between SrTiO3 and Si is the most important issue for obtaining high quality high-k gate dielectrics. The possible methods to improve the interfacial properties and the measurement techniques to characterize the interfacial layer are introduced and discussed.
10:45 AM - T12:Dielect
BREAK
T13: Ferroic Interfaces
Session Chairs
Thursday PM, November 30, 2006
Room 302 (Hynes)
11:15 AM - **T13.1
Ferroelectric/Electrode Interface Layers: Their Effects on Reliable Ferroelectric Polarization Switching and Possible Resistance Switching.
Paul McIntyre 1 , Ye Chen 1 , M. Kurasawa 1 , Rene Meyer 1
1 , Stanford University, Stanford, California, United States
Show AbstractThis presentation will review previous analyses of electrode interface layer effects on the switching characteristics and reliability of ferroelectric thin films, and the proposed origins of such layers in ferroelectric capacitors. Recent results on the formation of interface layers in Pb-based ferroelectric (epitaxial PbTiO3 and polycrystalline PZT) capacitors through local chemical reactions during electrode deposition will be described. We will present data obtained after intentional addition of ultrathin insulator (e.g. HfO2) interface layers by atomic layer deposition as a means of controlling electrostatic boundary conditions on ferroelectric capacitors. Both unintentionally-formed and intentionally-added insulating interface layers are found to greatly alter the electrical characteristics of Pb-based ferroelectric capacitors, including dc leakage conduction, switchable polarization, and opposite state retention. The possibility of engineering internal electrostatic potential barriers within layered ferroelectric/semiconductor structures for nonvolatile resistance switching memories will also be discussed.
11:45 AM - T13.2
Effect of Interfaces on the Properties of Polycrystalline Thin-Film PZT Ferroelectric Capacitors.
Lyuba Delimova 1 , Igor Grekhov 1 , Dmitri Mashovets 1 , Ilya Titkov 1 , Valentin Afanasjev 2 , Petr Afanasjev 2 , Galina Kramar 2 , Anatoly Petrov 2
1 Solid State Electronics Division, Ioffe Physicotechnical Institute Russian Academy of Sciences, St.Petersburg Russian Federation, 2 Microelectronics Department, State St.Petersburg Electrotechnical University "LETI", St.Petersburg Russian Federation
Show Abstract12:00 PM - T13.3
Materials Issues for Ferroelectric Memory: Self-assembled Ferroelectric Memory Arrays with bit densities of ~0.25 Tb/inch2 and the Effects of WO3 on Fatigue.
Paul Baxter 1 , J. McPhillips 1 , P. Evans 1 , X. Zhu 1 , R. Pollard 1 , R. Bowman 1 , J. Gregg 1 , F. Morrison 2 , J. Scott 2
1 Centre for Nanostructured Media, Queen's University, Belfast, County Antrim, United Kingdom, 2 Centre for Ferroics, Department of Earth Sciences, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom
Show AbstractWe report on two aspects of the study of ferroelectrics at reduced dimensions that are relevant to memory applications: Firstly, we report the successful fabrication of arrays of switchable nanocapacitors made by harnessing the self-assembly of materials. The structures are composed of an array of ~20-30nm diameter Pt nanowires, spaced about 50nm apart, which have been electrodeposited through nanoporous alumina thin films onto a lower electrode thin film layer on a silicon wafer. The top of the nanowire array has been coated in a thin film ferroelectric, and Au upper electrode. Both barium titanate (BTO) and lead zirconium titanate (PZT) have been used as the ferroelectric layer. The switched charge of PZT nanocapacitors yields rather saturated square hysteresis loops with remanent polarizations comparable to bulk, while, although the switching performance was inferior, the low-field characteristics of the BTO nanocapacitors show permittivities and dielectric losses comparable to conventional thin film heterostructures. While registration is not yet sufficient for commercial RAM production, this is nevertheless the highest density hard-wired FRAM capacitor array reported to date and compares favorably with atomic force microscopy (AFM) read-write densities. Secondly, we have investigated the effect that a thin layer (<10nm) of WO3 adjacent to the electrode-ferroelectric interface can have on the fatigue properties of lead-zirconium titanate (PZT) thin films. WO3 should readily absorb oxygen vacancy defects, and hence, according to the conventional view on fatigue, its presence should lead to fatigue-free PZT. We find that this is not the case, and will discuss both the data and its implications for current fatigue theories.
12:15 PM - T13.4
Mechanism of the Temperature-Dependent Polarity Reversal in Au-SrTiO3 Schottky Junctions
Harold Hwang 1 2 , Tomofumi Susaki 1 , Yusuke Kozuka 1
1 Dept. of Advanced Materials Science, University of Tokyo, Kashiwa-shi, Chiba, Japan, 2 , Japan Science and Technology Agency, Kawaguchi Japan
Show AbstractThe nature of electronic screening and lattice polarization at interfaces is the focus of recent research efforts in a wide range of contexts. This is, for example, a central issue in considering the ultimate thickness limits for ferroelectric stability in ultra-thin ferroelectric capacitors. For interfaces with SrTiO3, an “almost ferroelectric” perovskite with a large lattice dielectric response, induced polarization of the SrTiO3 near the interface can be the dominant screening mechanism. The proximity to a ferroelectric instability results in a highly nonlinear permittivity in electric field, which gives rise to unusual nonlinear band bending phenomena. We have studied the effects of this nonlinear permittivity in Au/Nb:SrTiO3 Schottky junctions. The Schottky barrier arising from the depletion of electrons in the SrTiO3 near the interface reflects the self-consistent permittivity in the internal electric field arising from band bending. Following the temperature dependence of the nonlinear permittivity, the Schottky barrier evolves as well. This results in striking phenomena, such as the temperature dependent reversal of junction polarity in current-voltage characteristics – that is, a reversal from a forward to a backward diode. We have modeled the junction band diagram using a model of the nonlinear permittivity in thermo-ionic field emission (thermally assisted tunneling), which captures the essential features of the electrical characteristics. We further discuss the limitations of using ε(q = 0) to describe the band diagram, and the contribution of the lattice as a general screening mechanism in complex oxide interfaces.
12:30 PM - T13.5
Electrostatic Mapping of the Doping Phase Diagram of the Colossal Magnetoresistive Oxide $La_xSr_{1-x}MnO_3$ Using the Ferroelectric Field Effect
Xia Hong 1 , Jason Hoffman 1 , Charles Ahn 1
1 Applied Physics, Yale University, New Haven, Connecticut, United States
Show AbstractWe have examined the doping phase diagram of the colossal magnetoresistive oxide $La_xSr_{1-x}MnO_3$ (LSMO) by electrostatically controlling the carrier concentration using the ferroelectric field effect. Epitaxial ferroelectric $Pb(Zr_0.2Ti_0.8)O_3$/LSMO heterostructures were fabricated using off-axis magnetron sputtering, with high quality crystalline structure and atomic level surface roughness being obtained. Using the polarization field of the ferroelectric, we have reversibly tuned the ferromagnetic Curie temperature and modulated the magnetotransport properties of the LSMO films. We find that electric field effect doping and chemical doping give nominally the same modulation in the normal state resistance and the magnetoresistance, but lead to different changes in anisotropic magnetoresistance. Working with LSMO films with $x$ close to 0.5, we observe a transition from a metallic to an insulating state by increasing the doping level, the opposite of what is observed at lower doping levels. This approach presents a way to systematically map out the effect of charge carriers on the electronic and magnetic states of correlated systems in a fashion that does not introduce disorder into the system.
12:45 PM - T13.6
Ferroelectric Gate FET Memory based on Conduction of SBT-SiON Interface.
Masanori Okuyama 1 , Takaaki Minami 1 , Bong-Yeon Lee 1 , Tkeshi Kanashima 1
1 Graduate school of engineering science, Osaka University, Toyonaka, Osaka, Japan
Show AbstractT14: Ferroic Heterostructures and Composites
Session Chairs
Thursday PM, November 30, 2006
Room 302 (Hynes)
2:30 PM - **T14.1
Microwave Magneto-electric Interactions in Multiferroics.
Gopalan Srinivasan 1 , Alexander Tatarenko 1 , Vincy Gheevarughese 1 , Mirza Bichurin 2
1 Physics, Oakland University, Rochester, Michigan, United States, 2 Institute of Electronic and Information System, Novgorod State University, Velikey Novgorod Russian Federation
Show AbstractThursday 11/30Transfer T14.11 4:45 to *T14.1 1:30 pmMicrowave Magneto-electric Interactions in Multiferroics. Gopalan Srivivasan
3:00 PM - T14.2
Electric Field Induced Switching of the Magneto-Optical Kerr Effect in Multiferroic Nanostructures.
Matthew Corbo 1 , Florian Straub 1 , Ying-Hao Chu 1 , Yuri Suzuki 1 , R. Ramesh 1
1 Materials Science & Engineering, University of California, Berkeley, Berkeley, California, United States
Show AbstractWe have demonstrated electric field induced switching of the magneto-optical Kerr effect (MOKE) signal in BiFeO3-CoFe2O4 (BFO-CFO) columnar nanostructures on SrRuO3-buffered, SrTiO3 (001) oriented substrates. The films spontaneously self-assemble into single crystalline ferrimagnetic (CFO) nanopillars embedded in a ferroelectric (BFO) matrix. These CFO nanopillars exhibit an aspect ratio (diameter : height) of approximately 1:3. A large magnetic anisotropy with an easy axis along the CoFe2O4 nanopillar’s long axis, perpendicular to the plane of the film, was observed in vibrating sample magnetometry (VSM) measurements. By using MOKE, where the plane of polarization of incident light is rotated upon reflection off of the surface of a magnetized material, we have the ability to probe and understand the magnetic behavior of these films in a non-invasive manner. We have chosen to perform the MOKE measurements in the polar geometry to probe the out-of-plane magnetization component. A Kerr rotation of approximately 0.5 degrees has been measured in these nanostructured thin films.We demonstrate the coupling between the ferrimagnetic CFO and ferroelectric BFO order parameters by observing the change in the MOKE signal induced by an applied electric field. A similar coupling has been observed in the reversal of the magnetization through electrical poling with a conducting cantilever during magnetic force microscopy measurements.[1] We have observed that the remnant Kerr rotation changes by as much as 15% after the application of a DC electric field is applied to the BFO matrix. This signal corresponds to an electric field induced change in the magneto-optical Kerr rotation of 0.075 degrees. The electric field is applied between transparent, conductive top electrodes (Indium Tin Oxide – ITO) and the SrRuO3 bottom electrode using a ferroelectric probe station. By further tuning the electrical properties of the capacitors and the electrical probe, we predict an electric field induced reversal of the Kerr rotation of up to 50%.References:[1] F. Zavaliche, et al., Nano Letters 5, 1793 (2005).
3:15 PM - T14.3
Multiferroic Behavior in Pb(Zr0.52Ti0.48)O3-Co0.9Zn0.1Fe2O4 Nanocomposite Thin Films via a Solution Processing.
Hong-cai He 1 , Jing Wang 1 , Jian-ping Zhou 1 , Ce-Wen Nan 1
1 Department of Materials Science and Engineering, Tsinghua University, Beijing, Beijing, China
Show Abstract3:30 PM - T14.4
Magnetoelectric Coupling in Multiferroic Trilayers Based on Terfenol-PZT- Terfenol.
Junyi Zhai 1 , Shuxiang Dong 1 , Jiefang Li 1 , Dwight Viehland 1 , Mirza Bichurin 2 , Vladimir Petrov 2 , Dmitry Filippov 2 , Cewen Nan 3
1 MSE, Virginia Tech, Blacksburg, Virginia, United States, 2 Institute of Electronic and Informative Systems, Novgorod State University, Novgorod Russian Federation, 3 MSE, Tsinghua University, Beijing China
Show Abstract3:45 PM - T14.5
Natural Multiferroic Superlattices.
Mark Zurbuchen 1 , Mike Biegalski 2 , Rafael Freitas 3 , Mark Wilson 3 , Peter Schiffer 3 , M. Roeckrath 5 , Jürgen Schubert 5 , Steven Fulk 4 , David Comstock 4 , Darrell Schlom 4
1 Ceramics Division, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 2 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 3 Physics Department and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania, United States, 5 Institute of Bio and Nanosystems, Forschungszentrum Jülich, Jülich Germany, 4 Dept of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractFew natural phases exhibiting simultaneous ferroelectric and ferromagnetic behavior exist due to the physical mechanisms of the two phenomena being for the most part mutually exclusive.[N. A. Hill, J. Phys. Chem. B 104, 6694 (2000).] Natural superlattice materials are one potential route for circumventing these limitations, since they are effectively nanocomposites of crystal structural units. A new class of potential magnetoelectric superlattices is prepared by charge-mediated synthesis to yield single-phase films of new ferroic materials, incorporating ferrromagnetic BiMnO3 into the perovskite substructure of ferroelectric Bi4Ti3O12. Synthesis and characterization of these materials, such as Bi7Mn3.75Ti2.25O21, will be presented. Results of magnetic measurements confirm ferromagnetism, and results of electrical measurements will be presented, along with structural and microstructural characterization of this pure n = 6 Aurivillius phase. This is also the first report of any epitaxial Aurivillius phase incorporating manganese.
4:30 PM - T14.6
Giant Magnetoelectric Gyration Effect in Tb1-xDyFe2-y/Pb(Zr,Ti)O3 Laminated Composite
Shuxiang Dong 1 , Junyi Zhai 1 , Jie-Fang Li 1 , Dwight Viehland 1 , Mirza Bichurin 2
1 Materials Science & Engineering, Virginia Tech, Blacksburg, Virginia, United States, 2 Institute of Electronic and Informative Systems, Novgorod State University, Veliky Novgorod Russian Federation
Show AbstractA giant current-to-voltage (I-V) gyration effect was found in magnetostrictive Tb1-xDyFe2-y and piezoelectric Pb(Zr,Ti)O3 layers laminated composite. This I-V gyration is attributed to magneto-elastic and electromechanical couplings, i.e., magnetoelectric (ME) coupling. A ME gyration model was built, which predicted that the I-V conversion is modulated by a frequency transfer function ZR(f) and the maximum is at the electromechanical resonance. Experimentally, a giant conversion coefficient up to 2500V/A associating a high voltage gain was observed.
4:45 PM - T14.7
Controlled Switching of Magnetization with an Electric Field in Self-Assembled Multiferroic Nanostructures.
Florin Zavaliche 1 2 , H. Zheng 1 2 , F. Straub 1 2 , M. Cruz 1 2 3 , P. Yang 1 , R. Ramesh 1 2
1 Materials Science and Engineering, University of California, Berkeley, California, United States, 2 Physics, University of California, Berkeley, California, United States, 3 , CCMC-UNAM, Ensenada, B.C., Mexico
Show AbstractSelf-assembled ferroelectric-ferrimagnetic epitaxial films with composition BiFeO3-CoFe2O4 show strong magnetoelectric coupling due to their matrix-pillar morphology. Under an applied electric field, half of the ferrimagnetic nanopillars reverse their magnetization, regardless of the relative orientation between the ferroelectric and magnetic polarizations. This picture is in agreement with the simple mechanism of a transient alteration of pillar magnetic anisotropy and/or coercivity due to interfacial stresses following the ferroelectric switching. Our efforts aimed at controlling the electrical switching of magnetization in all nanopillars at ambient conditions. To do so, a weak, uniform magnetic field was superimposed to the switching electric field. Consequently, we were able to selectively switch pillars with only one magnetic configuration. In this way, the reversal of magnetization with an electric field was successfully controlled and the magnetoelectric coupling effect became deterministic and unidirectional.This work has been supported in part by ONR under a MURI program.
5:00 PM - T14.8
Thermodynamics of Formation and Electro-Magnetic Coupling of Self-Assembling Multiferroic Thin Film Nanostructures.
Julia Slutsker 1 , Alexander Roytburd 2
1 , NIST, Gaithersburg, Maryland, United States, 2 Materials Science and Engineering, University of Maryland, College Park, Maryland, United States
Show Abstract5:15 PM - T14.9
Exchange Anisotropy in Multiferroic Complex Oxide Heterostructures.
Lane Martin 1 3 , Ying-Hao Chu 1 3 , Qian Zhan 1 3 , Micky Barry 2 3 , Kilho Lee 1 3 , Matt Langner 2 3 , Colleen Kantner 2 3 , Joseph Orenstein 2 3 , Yuri Suzuki 1 3 , R. Ramesh 1 2 3
1 Materials Science and Engineering, University of California, Berkeley, Berkeley, California, United States, 3 , Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 Physics, University of California, Berkeley, Berkeley, California, United States
Show Abstract5:30 PM - T14.10
Functional Properties of Multiferroic Superlattices.
Arjen Molag 1 2 , Guus Rijnders 1 2 , Dave H.A. Blank 1 2
1 Faculty of Science and Technology, University of Twente, Enschede Netherlands, 2 , Mesa+ Institute for Nanotechnology, Enschede Netherlands
Show Abstract5:45 PM - T14.11
Dielectric and Magnetic Properties of Multiferroic BiCrO3 and BiFeO3 Epitaxial Films and Superlattices.
Dae Ho Kim 1 , Ho Nyung Lee 1 , Maria Varela 1 , Hans Christen 1
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractThursday 11/30Transfer T3.23 (poster) toT14.11 4:45 pmDielectric and Magnetic Properties of Multiferroic BiCrO3 and BiFeO3 Epitaxial Films and Superlattices. Dae Ho Lim