Symposium Organizers
Masashi Kawasaki Tohoku University
Jochen Mannhart University of Augsburg
Ramamoorthy Ramesh University of California-Berkeley
Darrell G. Schlom The Pennsylvania State University
L1: Theory & Experiment I
Session Chairs
Masashi Kawasaki
Thilo Kopp
Tuesday PM, April 10, 2007
Room 3011 (Moscone West)
9:00 AM - *L1.1
Pathways to New Magnetic Materials without Traditional Magnetic Elements.
George Sawatzky 1
1 , UBC Vancouver, Vancouver, British Columbia, Canada
Show Abstract9:45 AM - **L1.2
Theory of Novel Phenomena at Interface of Strongly Correlated Electronic Systems.
Naoto Nagaosa 1
1 , The University of Tokyo, Tokyo Japan
Show AbstractThe interfaces of strongly correlated electronic systems are a new frontier for the fundamental sciences and applications. We can naturally expect the broken inversion symmetry, which leads to various interesting phenomena especially combined with the broken time-reversal symmetry, i.e., magnetism.In this talk, I will discuss about several theoretical proposals for the new functionalities at the interface using the electron motion perpendicular and parallel to it as listed below.1. Interfacial Mott transition A model for the interface between a usual metal and a Mott insulator is studied theoretically in terms of the density matrix renormalization group method [1]. The numerical results are reproduced quantitatively by a self-consistent Poisson equation with the density-chemical potential relationship for the Mott insulator. According to this mean field analysis, a scenario for the CER function is proposed assuming the first order Mott phase transition. [1] T. Oka and N. Nagaosa, Physical Review Letters 95, 266403 (2005)2. Quantum mechanism of FRAM and ferroelectricity enhanced by disorder As the thickness of the insulating layer becomes of the order of nano-scale, the wavefunctions are connected between the two sides, and the charge transfer associated with the change of the atomic position is sensitive to the quantum interference effect. We analyze this quantum ferroelectricity in nano-scale and propose an enhanced electric polarization by disorder.[2] Shigeki Onoda, Chyh-Hong Chern, Shuichi Murakami, Yasushi Ogimoto, Naoto Nagaosa, cond-mat/06052153. Multiferroic Phenomena at Interface As mentioned above, the inversion symmetry is broken strongly at the interface, and leads to many interesting phenomena including anomalous Hall effect, spin Hall effect, magneto-chiral effect etc., when combined with the magnetic properties. I will present some theoretical predictions in this direction.
10:15 AM - **L1.3
Correlation Effects at Surfaces.
Ansgar Liebsch 1
1 , Research Center, Juelich Germany
Show AbstractElectronic correlations at surfaces may differ from those in the bulk for a variety of reasons, depending on single-particle as well as many-body properties of the material. We use dynamical mean field theory in conjunction with multi-band Quantum Monte Carlo and exact diagonalization to evaluate quasi-particle spectra of several stronglycorrelated transition metal oxides. The understanding of how the presence of the surface modifies correlation induced spectral features is particularly important for the analysis of photoemission spectra because of the intrinsic surface sensitivity of this spectroscopy.
11:15 AM - **L1.4
New Electronic Structure In Short Period Complex Oxide Superlattices.
James Eckstein 1 , Xiaofang Zhai 1 , Chandra Mohapatra 1 , Maitri Warusawithana 2 , Anand Bhattacharya 3 , Jian-Min Zuo 4 , Amish Shah 4 , Bing Jiang 4 , Jian Guo Wen 5 , Hao Chen 4
1 Department of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana-Champaign, Urbana, Illinois, United States, 2 Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States, 3 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 4 Department of Materials Science and Engineering and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana-Champaign, Urbana, Illinois, United States, 5 Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana-Champaign, Urbana, Illinois, United States
Show AbstractAt heterojunctions between different oxide perovskite phases both lattice and electronic structure is modified by the junction. One interesting question that several groups have studied is just how far into the neighboring materials these perturbations extend. We have studied this for insulating phases as well as conducting phases. For insulating phases it appears that the lattice distortions are healed in a layer about one unit cell thick. By stacking different materials each of which is only a single unit cell thick we have obtained materials that exhibit new properties determined by the stacking architecture. For example, superlattices that lack inversion symmetry have a built-in polarization that is controlled by the direction of the strain asymmetry. For conducting phases, the electronic structure also seems to be modified mainly in a layer only a few unit cells thick. We have studied this in superlattices of SrTiO3 and LaMnO3 in which we vary the thickness of the layers. We use optical conductivity to probe the electronic structure in the near infrared to near ultraviolet spectral region. The conductivity is close to the average of the two constituents, but differs in certain spectral regions, especially for the films with the thinnest supercells.This work was supported by the Department of Energy Basic Energy Sciences program at the Fredrick Seitz Materials Research Laboratory at the University of Illinois, Urbana, IL.
11:45 AM - **L1.5
First-principles Theory of Interfacial Electronic Structures, Mechanical and Ferroelectric Stabilities of Electroceramic Thin-film Heterostructures.
Christian Elsaesser 1 4 , Jan-Michael Albina 1 4 , Yoshitaka Umeno 2 4 , Bernd Meyer 3 , Matous Mrovec 4 1 , Peter Gumbsch 4 1
1 , Fraunhofer-Institut für Werkstoffmechanik, Freiburg Germany, 4 Institut für Zuverlässigkeit von Bauteilen und Systemen, Universität Karlsruhe, Karlsruhe Germany, 2 Graduate School of Engineering, Kyoto University, Kyoto Japan, 3 Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, Bochum Germany
Show Abstract12:15 PM - **L1.6
Photoemission Spectroscopy of Oxide Interfaces.
Atsushi Fujimori 1
1 Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan
Show Abstract12:45 PM - L1.7
Correlation Driven Charge and Magnetic Order at Digital Perovskite Heterostructures: LaTiO3/SrTiO3 and LaAlO3/SrTiO3.
Rossitza Pentcheva 1 , Warren Pickett 2
1 Section Crystallography, Department of Earth and Environment, University of Munich, Munich Germany, 2 Department of Physics, University of California, Davis, California, United States
Show AbstractL2: Theory & Experiment II
Session Chairs
Mikk Lippmaa
Naoto Nagaosa
Tuesday PM, April 10, 2007
Room 3011 (Moscone West)
2:30 PM - *L2.1
Excitonic-Induced Superconductivity By The Presence Of Thallium Ions.
Theodore Geballe 1
1 Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California, United States
Show AbstractRecent experiments by Matsushita et al(1) lead to the conclusion that the superconductivity found in semiconducting PbTe doped with Tl ions of a few times 10/20 per cc (the solubility limit) is caused by an excitonic mechanism. They find 1) the superconducting properties are fit by weak-coupled BCS (mean-field) theory 2) the Tcs as a function of doping are roughly two orders of magnitude higher than comparably doped chalcogen semiconductors and an order of magnitude higher than electron-doped SrTiO3 3)No superconductivity is found upon doping in the same concentration range with cations other than Tl. The above facts virtually eliminate the possibility that the superconductivity might be due to local phonon modes to the many valley structure of the valence band. The further findings of Matsushita et al(2) show that the observed low temperature resistance minima are fit by a charge-Kondo mode assuming a near degeneracy of the +1 and +3 Tl ionic states(the +2 state of Tl is at much higher energy as evident from the chemistry of Tl ). The assumption is justified by measurements of the Hall number. The exitonic pairing mechanism is thus simply the exchange of paired electrons between two Tl valence states and the PbTe valence band. Empirical evidence strongly suggests that the TlO charge reservoir layers in Tl high Tc cuprates, and likewise HgO and BiO layers in their respective cuprates are responsible for large enhancements in Tc presumably by exchanging pairs of carriers with the CuO2 layers.1. Y. Matsushita, H. Bluhm, T.H. Geballe, and I.R. Fisher, Phys. Rev. Lett. 94, 157002 (2005).2. Submitted
3:15 PM - *L2.2
Multiferroics – From Frustrated Lattice to Tailored Interface.
Yoshi Tokura 1 2 3
1 , Department of Applied Physics, University of Tokyo, Tokyo Japan, 2 , Correlated Electron Research Center (CERC), AIST, Tsukuba Japan, 3 , ERATO Multiferroics Project, JST, Tokyo Japan
Show Abstract4:30 PM - **L2.3
Enhanced Thermal Transport in Multilayered Devices Arising from Electronic Charge Reconstruction.
Jim Freericks 1
1 Physics, Georgetown University, Washington, District of Columbia, United States
Show Abstract5:00 PM - **L2.4
Competition Between High Tc Superconductivity and Ferromagnetism in Oxide Multilayers.
Christian Bernhard 1 , Justin Hoppler 1 , Alan Drew 1 , Jochen Stahn 2 , Christof Niedermayer 2 , Elvezio Morenzoni 2 , Andreas Suter 2 , Thomas Prokscha 2 , Hans-Ulrich Habermeier 3 , Bernhard Keimer 3
1 physics, university of fribourg, Fribourg Switzerland, 2 , Paul Scherrer Institut PSI, PSI Villigen Switzerland, 3 , Max-Planck-Institut FKF, PSI Villigen Germany
Show Abstract5:30 PM - **L2.5
Electronic Configuration in Perovskite Interfaces: Epitaxial LaMnO3/SrTiO3 Structures.
Hans Christen 1 , Maria Varela 1 , Leon Petit 2 , Dae Ho Kim 1 , Ho Nyung Lee 1 , Thomas Schulthess 2
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 Computer Science and Mathematics Division, Oak Ridge National Laboartory, Oak Ridge, Tennessee, United States
Show Abstract
Symposium Organizers
Masashi Kawasaki Tohoku University
Jochen Mannhart University of Augsburg
Ramamoorthy Ramesh University of California-Berkeley
Darrell G. Schlom The Pennsylvania State University
L3: Theory & Experiment III
Session Chairs
Hans-Martin Christen
Rossitza Pentcheva
Wednesday AM, April 11, 2007
Room 3011 (Moscone West)
9:00 AM - **L3.1
Correlated Electron Heterostructures: Theory.
Andrew Millis 1
1 Physics, Columbia University, New York, New York, United States
Show AbstractIt has now become possible to fabricate high quality oxide "heterostructures": multilayer systems in which one or more unit cell thick films of one material with interesting electronic properties (such as a colossal magnetorestance manganite) are interleaved with one or more unit cell thick films of another, with essentially perfect epitaxy. This talk will summarize the present status of the field, including challenges and implications. Recent progress in theoretical analysis of (001) ($A_nA'_mBO_3$) heterostructures will be summarized, including studies of Mott insulator band insulator [1,2] and 'colossal' magnetoresistance manganite [3] systems will be presented, and placed in the context of a general picture [4] of behavior of surface and interface phenomena in correlated electron materials. Strengths and weaknesses of presently available theoretical techniques will be outlined. The crucial importance of characterizing the charge profile will be demonstrated. The work presented here has been done in collaboration with S. Okamoto, N. Spaldin and C. Lin and is supported by the U.S. DOE under contract ER-46169, the JSPS (SO) and the Columbia University Materials Research Center (C.L.). [1] S. Okamoto and A. J. Millis, Nature \textbf{428} 630-2 (2004)[2] Satoshi Okamoto, Andrew J. Millis, Nicola A. Spaldin, Phys. Rev. Lett. 97, 056802 (2006).[3] C. Lin, S. Okamoto, and A. J. Millis Phys. Rev. B 73, 041104/1-4 (2006).[4] A. J. Millis, in "Thin Films and Heterostructures for Oxide Electronics" Ogale, Satishchandra B. (Ed.) Springer Verlag,(2005).
L5: Electron Gases and FETs II
Session Chairs
Gertjan Koster
Celine Lichtensteiger
Wednesday PM, April 11, 2007
Room 3011 (Moscone West)
9:00 AM - **L10.1
Resistance Switching and Memory Effect at Perovskite-Oxide Interfaces.
Akihito Sawa 1 , Takeshi Fujii 1 2 , Masashi Kawasaki 1 2 , Yoshi Tokura 1 3
1 Correlated Electron Research Center (CERC), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Japan, 2 Institute for Materials Research, Tohoku University, Sendai Japan, 3 Department of Applied Physics, University of Tokyo, Tokyo Japan
Show AbstractReversible resistance switching effect observed in a wide variety of transition metal oxide junctions attracts considerable attention because of the potential for nonvolatile memory applications such as resistance random access memory. Although intensive studies of the resistance switching effect in both experiment and theory have been carried out, the thorough understanding of the driving mechanism has still not been attained. In the present study, the resistance switching effect has been investigated for perovskite-oxide heterojunctions consisting of various metal electrodes and p-type or n-type semiconducting oxides such as Pr0.7Ca0.3MnO3 or Nb-doped SrTiO3, respectively. The metal/perovskite-oxide heterojunction devices show either rectifying current-voltage (I-V) characteristics similar to those of a Schottky junction or ohmic behavior, depending on the work function of the metals. In addition, the rectifying I-V characteristics have large hysteresis. Corresponding to the hysteresis directions, the junction devices show reversible resistance switching upon the application of voltage pulses. When we insert several unit cells of various oxide lattices at the metal/perovskite-oxide interfaces, the resistance switching behaviors are substantially modified, indicating that the resistance switching takes place at the interfaces. On the basis of the experimental results, we propose a possible origin of the resistance switching effect, that is a charging effect at the Schottky-like metal/perovskite-oxide interfaces.This work was supported in part by Industrial Technology Research Grant Program in 2005 from New Energy and Industrial Technology Development Organization (NEDO) of Japan.
L3: Theory & Experiment III
Session Chairs
Hans-Martin Christen
Rossitza Pentcheva
Wednesday PM, April 11, 2007
Room 3011 (Moscone West)
9:30 AM - **L3.2
Interfaces and Defects in Perovskite Heterostructures.
David Muller 1 , Lena Fitting Kourkoutis 1 , Naoyuki Nakagawa 2 , Yasushi Hotta 2 , T. Susaki 2
1 School of Applied and Engineering Physics, Cornell University, Ithaca, New York, United States, 2 Department of Advanced Materials, University of Tokyo, Kashiwa, Chiba, Japan
Show AbstractElectron energy loss spectroscopy (EELS) provides direct information on the local electronic structure of a material at the atomic scale. In ionic systems, EELS measurements of oxygen vacancies and cation formal valences give insight and place remarkable constraints on the structure and stability of heterointerfaces and defects. This is of considerable importance to the field of oxide electronics and ferroelectrics, where been the growth of atomically-abrupt heterointerfaces has been a central goal. However, when the interfaces are between polar and nonpolar layers, electrical and atomic abruptness turn out to be mutually incompatible goals. This is the bulk analogy of the surface reconstructions found in polar systems where a material terminated along a bulk polar plane has a net charge and a divergent surface energy. The mechanisms by which compensating charges can be introduced are varied and sensitive to growth and substrate conditions, ranging from electronic reconstructions in mixed valence systems to changes in interface stoichiometry and the creations of defects such as oxygen vacancies. This is illustrated for interfaces between SrTiO3 and LaAlO3, LaTiO3 and other related systems such as Vanadates. This work was supported under the ONR EMMA MURI monitored by Colin Wood and by the Cornell NSF-MRSEC.
L5: Electron Gases and FETs II
Session Chairs
Gertjan Koster
Celine Lichtensteiger
Wednesday PM, April 11, 2007
Room 3011 (Moscone West)
9:30 AM - **L10.2
Resistance Switching and Filament Formation in Binary Transition-Metal Oxides.
Kohei Fujiwara 1 , Takumi Nemoto 1 , Hiroshi Tomita 1 2 , Yosuke Konno 1 , Marcelo Rozenberg 1 , Isao Inoue 2 , Hiroyuki Akinaga 2 , Hidenori Takagi 1 2
1 Department of Advanced Materials, University of Tokyo, Kashiwa Japan, 2 , AIST, Tsukuba Japan
Show AbstractNon-polar resistance switching between high (HR) and low resistance (LR) states in transition metal oxides, such as NiO, Fe2O3, CuO, has been attracting considerable interest because of their potential application as a memory device. The mechanism of switching in these binary transition metal oxide devices, however, has been remaining yet to be clarified. The formation of conducting “filament” within the transition metal oxide in the LR state was suggested as a key to understand the mechanism. In capacitor-type devices with transition metal oxide thin film sandwiched by two metal electrodes, the resistance in LR state was indeed found to be almost independent of the electrode area, supporting for the formation of a filament. In contrast, the resistance in HR state was essentially inversely scaled by the electrode area. To examine the presence of such filament, Ni/CuO/Ni “planar” devices with CuO channel length of 1-10 μm were fabricated. This enabled us to visualize CuO channel region between the two Ni electrodes directly by SEM at each stage of switching operation, including forming (initial switching to LR state), set (switching from HR to LR) and reset (switching from LR to HR). We found the formation of bridge like path (melted region) between the two Ni electrodes after the forming process. We will demonstrate that this bridge is responsible for the conduction in LR state and that the presence of “single” filament is a key ingredient for the repeatable resistive switching in binary transition metal oxides. The temperature dependence of resistance in LR state was found to be metallic down to 4K, suggesting the presence of filamentary path of Cu metal. We speculate that oxidation and reduction of Cu is underlying mechanism of resistance switching.
L3: Theory & Experiment III
Session Chairs
Hans-Martin Christen
Rossitza Pentcheva
Wednesday PM, April 11, 2007
Room 3011 (Moscone West)
10:00 AM - **L3.3
Ab initio Calculations of Complex Oxide Interfaces.
Nicola Spaldin 1
1 Materials Department, UC Santa Barbara, Santa Barbara, California, United States
Show AbstractL5: Electron Gases and FETs II
Session Chairs
Gertjan Koster
Celine Lichtensteiger
Wednesday PM, April 11, 2007
Room 3011 (Moscone West)
10:00 AM - **L10.3
Role of Oxygen Vacancies in Cr-doped SrTiO3 Resistance-change Memory.
Gerhard Ingmar Meijer 1 , S. Karg 1 , M. Janousch 2 , U. Staub 2 , D. Widmer 1 , B. Andreasson 2 , J. Bednorz 1
1 , IBM Zurich Research Laboratory, Rueschlikon Switzerland, 2 , Swiss Light Source, Paul Scherrer Institut, Villigen Switzerland
Show AbstractL3: Theory & Experiment III
Session Chairs
Hans-Martin Christen
Rossitza Pentcheva
Wednesday PM, April 11, 2007
Room 3011 (Moscone West)
10:30 AM - L3.4
Electronic Interface States in Cuprate-Titanate Heterostructures.
Natalia Pavlenko 2 1 , Ilya Elfimov 3 , George Sawatzky 3 , Thilo Kopp 1
2 , Institute of Condensed Matter Physics, Lviv Ukraine, 1 Center for Electronic Correlations and Magnetism, Universität Augsburg, Augsburg Germany, 3 Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada
Show AbstractHeterostructures consisting of YBa2Cu3O7-δ (YBCO) films grown on SrTiO3 (STO) layers are of essential importance due to their applications in superconducting field effect devices. However, despite they show great promise for technological applications, a number of interface-related effects recently observed in such heterostructures cannot be satisfactorily explained by the standard field-doping concept. Whereas Tc shifts of 5–15 K have been observed in underdoped cuprate films, the critical temperature is not significantly changed by the electrostatic gate field in overdoped films. In many cases, an insulating state was actually identified. To deal with these issues, we investigate the electronic phase at the YBCO-STO interface within two complementary approaches: we study electronic states at interfaces between YBa2Cu3O6 and STO using a local spin density approximation with intra-atomic Coulomb repulsion (LSDA+U) in order to determine the charge profile of the interface layers.1 Moreover, we apply slave boson techniques to qualify the charge correlations in the cuprate film.2 From the DFT-evaluation, we find a metallic state with the hole carriers concentrated substantially in the CuO2 layers and in the first interface TiO2 and SrO planes. This effective interface doping appears due to the polarity of interfaces, caused by the first incomplete copper oxide unit cell. Our analytical study is based on an extended Hubbard model for the cuprate film. The interface is implemented by a coupling to the electron and phonon degrees of freedom of the dielectric oxide layer. We predict that the doped charge in the film can be localized by the interface coupling and we find that an electronic ordering in the film is associated with a strongly inhomogeneous polaron effect. Eventually, we discuss the consequences of effective interface doping and coupling for the control of the superconducting properties in engineered field-effect devices.
1 N. Pavlenko, I. Elfimov, T. Kopp, and G.A. Sawatzky, cond-mat/0605589 (2006).
2 N. Pavlenko and T. Kopp, Phys. Rev. Lett. 97, 187001, (2006).
L5: Electron Gases and FETs II
Session Chairs
Gertjan Koster
Celine Lichtensteiger
Wednesday PM, April 11, 2007
Room 3011 (Moscone West)
10:30 AM - L10.4
Memory Switching Behaviors of NiOx Thin Films.
Seohyoung Chang 1 , Seung Chul Chae 1 , Chunli Liu 1 , Sin Bum Lee 1 , Dong-Wook Kim 2 , Chang Uk Jung 3 , Tae Kwon Song 4 , DongChul Kim 5 , Ranju Jung 5 , Meongjae Lee 5 , Sunae Seo 5 , Tae Won Noh 1
1 Dept. of Physics and Astronomy, Seoul National University, Seoul Korea (the Republic of), 2 Dept. of Applied Physics, Hanyang University, Ansan, Kyeonggi, Korea (the Republic of), 3 Dept. of Physics, Hankuk University, Yongin, Kyeonggi, Korea (the Republic of), 4 School of Nano & Advanced Materials, Changwon National University, Changwon, Gyeongnam, Korea (the Republic of), 5 Semiconductor Device & Material Laboratory, Samsung Advanced Institute of Technology, Suwon, Kyeonggi, Korea (the Republic of)
Show AbstractL3: Theory & Experiment III
Session Chairs
Hans-Martin Christen
Rossitza Pentcheva
Wednesday PM, April 11, 2007
Room 3011 (Moscone West)
10:45 AM - L3:TEIII
BREAK
L5: Electron Gases and FETs II
Session Chairs
Gertjan Koster
Celine Lichtensteiger
Wednesday PM, April 11, 2007
Room 3011 (Moscone West)
10:45 AM - L10.5
Mechanism of Electric-field-induced Resistance Switching in Metal Electrode / Epitaxial Pr0.7Ca0.3MnO3/LaNiO3 Electrode Stacked Structure.
Kenta Tsubouchi 1 , Isao Ohkubo 1 , Takayuki Harada 1 , Hiroshi Kumigashira 1 , Yuji Matsumoto 2 , Kenji Itaka 3 , Tsuyoshi Ohnishi 4 , Mikk Lippmaa 4 , Hideomi Koinuma 5 , Masaharu Oshima 1
1 Department of Applied Chemistry, The University of Tokyo, Tokyo Japan, 2 Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan, 3 CREST, Japan Science and Technology Agency, Kawaguchi, Saitama, Japan, 4 Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba, Japan, 5 Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba, Japan
Show Abstract11:00 AM - L5:EG II
BREAK
L3: Theory & Experiment III
Session Chairs
Hans-Martin Christen
Rossitza Pentcheva
Wednesday PM, April 11, 2007
Room 3011 (Moscone West)
11:15 AM - **L3.5
Oxide Heterostructures for Field-effect Devices.
Mikk Lippmaa 1 , Keisuke Shibuya 1 , Tsuyoshi Ohnishi 1 , Taisuke Sato 1 , Kei Takahashi 2
1 Institute for Solid State Physics, University of Tokyo, Kashiwa-shi, Chiba, Japan, 2 Department of Advanced Materials Science, University of Tokyo, Kashiwa-shi, Chiba, Japan
Show AbstractL5: Electron Gases and FETs II
Session Chairs
Gertjan Koster
Celine Lichtensteiger
Wednesday PM, April 11, 2007
Room 3011 (Moscone West)
11:30 AM - L10.6
Interface Formation Between Perovskite Manganese Oxide Epitaxial Thin Films and Various Metal Electrodes Applicable for Resistance Random Access Memory.
Isao Ohkubo 1 , Kenta Tsubouchi 1 , Hiroshi Kumigashira 1 2 , Kenji Itaka 2 , Yuji Matsumoto 3 , Tsuyoshi Ohnishi 4 , Mikk Lippmaa 4 , Hideomi Koinuma 2 5 , Masaharu Oshima 1 2
1 Dept. of Applied Chemistry, The University of Tokyo, Tokyo Japan, 2 , CREST, Japan Science & Technology Corporation (JST) , Kawaguchi-shi, Saitama Japan, 3 Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama Japan, 4 Institute for Solid State Physics, The University of Tokyo, Chiba Japan, 5 Graduate School for Frontier Sciences, The University of Tokyo, Chiba Japan
Show AbstractL3: Theory & Experiment III
Session Chairs
Hans-Martin Christen
Rossitza Pentcheva
Wednesday PM, April 11, 2007
Room 3011 (Moscone West)
11:45 AM - **L3.6
Magnetism at Surfaces and Interfaces via Complex Oxide Heteroepitaxy.
Yuri Suzuki 1 2 , Rajesh Chopdekar 1 3 , Brittany Nelson-Cheeseman 1 , Yayoi Takamura 1 , J. Alexander Liddle 2 , Bruce Harteneck 2 , Elke Arenholz 2 , Andreas Scholl 2 , Andrew Doran 2 , Darren Dale 3 , Aaron Fleet 3 , Joel Brock 3
1 , University of California-Berkeley, Berkeley, California, United States, 2 Materials Science Division, LBNL, Berkeley, California, United States, 3 , Cornell University, Ithaca, New York, United States
Show AbstractL5: Electron Gases and FETs II
Session Chairs
Gertjan Koster
Celine Lichtensteiger
Wednesday PM, April 11, 2007
Room 3011 (Moscone West)
11:45 AM - L10.7
A New Bipolar Resistive Switching Mechanism in a Pt/TiO2/Pt Thin Film Stack.
Doo Seok Jeong 1 , Herbert Schroeder 1 , Rainer Waser 1
1 Institute of solid state research, Research center Juelich, Juelich, NRW, Germany
Show AbstractL4: Electron Gases and FETs I
Session Chairs
Wednesday PM, April 11, 2007
Room 3011 (Moscone West)
12:15 PM - **L4.1
Transport Properties Observed at Hetero-interfaces of LaAlO3 on SrTiO3; Intrinsic or Extrinsic Interface Effect?
Gertjan Koster 1
1 GLAM, Stanford University, Stanford, California, United States
Show Abstract12:45 PM - L4.2
Interface Effects on Layer Doping in Cuprate / Manganite Interfaces.
Javier Garcia- Barriocanal 1 , Alberto Rivera 1 , Zouhiar Sefrioui 1 , Carlos Leon 1 , Maria Varela 2 , Steven J. Pennycook 2 , Jacobo Santamaria 1
1 , Universidad Complutense de Madrid, Madrid Spain, 2 Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractL6: Poster Session
Session Chairs
Jochen Mannhart
Darrell Schlom
Thursday AM, April 12, 2007
Salon Level (Marriott)
2:30 PM - **S3.1
Hierarchically Porous Oxides, Hybrids and Polymers via Sol-gel Accompanied by Phase Separation.
Kazuki Nakanishi 1
1 Chemistry, Kyoto University, Graduate School of Science, Kyoto, Kyoto, Japan
Show Abstract3:00 PM - S3.2
Recent Advances in Hybrid Particle Technology and use in Reveresed-Phase Chromatographic Applications.
Kevin Wyndham 1 , Nicole Lawrence 1 , Kenneth Glose 1 , Jim Cook 1 , Daniel Walsh 1 , Darryl Brousmiche 1 , Pamela Iraneta 1 , Bonnie Alden 1 , Cheryl Boissel 1 , Thomas Walter 1
1 CRD, Waters Coporation, Milford, Massachusetts, United States
Show AbstractThe development of highly spherical, porous, hybrid particles for use as chromatographic packing materials has advanced the field of reversed-phase HPLC. Hybrid particles afford similar selectivity and method development as silica-based reversed-phase columns, while greatly improving the alkaline chemical stability of these materials. Since our initial commercialization of hybrid particles, based on the mixed hydrolytic condensation of methytriethoxysilane with tetraethoxysilane in 1999, our research group has continued to explore the use of a wide variety of hybrid formulations for chromatographic applications.In this report, we will review the synthesis and characterization of hybrid particles based on different organofunctional silane monomers. In particular we will explore the synthesis of spherical porous particles based on mixed condensation reactions using 1,2-bis(triethoxysilyl)ethane, and other organofunctional silane monomers that contain synthetically relevant pendant groups (e.g., amino, hydroxyl, methacryloxy groups).
3:15 PM - **S3.3
New Applications of Proteins Immobilized in Mesostructured Silicas: Selective Metal Removal and Selective Degradation of Pollutants.
Anne Galarneau 1 , Aude Falcimaigne 1 , Lai Truong Phuoc 1 , Gilbert Renard 1 , Francois Fajula 1
1 , CNRS, Montpellier France
Show Abstract3:45 PM - S3.4
Structural Ordering of Self-Assembled Alkylenesilicates.
Veronica de Zea Bermudez 1 , Silvia C. Nunes 1 , Rute Sa Ferreira 2 , Luis Dias Carlos 2 , Denis Ostrovskii 3 , Joao Rocha 4
1 Chemistry, University of Trás-os-Montes e Alto Douro, Vila Real Portugal, 2 Physics, University of Aveiro, Aveiro Portugal, 3 Applied Physics, Chalmers University of Tecnology, Goteborg Sweden, 4 Chemistry, University of Aveiro, Aveiro Portugal
Show Abstract4:30 PM - **S3.5
Soft Epitaxy: Surfactant-mediated Generation of Iso-oriented Crystalline, Mesoporous Metal Oxide Layers
Bernd Smarsly 1 , Torsten Brezesinski 2
1 Colloid Chemistry, Max Planck Institute of Colloids and Interfaces, Potsdam Germany, 2 Department of Chemistry and Biochemistry, UCLA, Los Angeles, California, United States
Show AbstractMesoporous metal oxide thin films have attracted significant attention due to their potential use in photocatalysis, redox reactions, sensing etc. The most straightforward preparation method involves sol-gel chemistry in combination with a suitable structure-directing block copolymer (evaporation-induced self-assembly, EISA). Typically, a substrate is dip-coated by a solution containing a metal salt as precursor in the presence of a template and heat-treated afterwards to form the of the corresponding crystalline mesoporous oxide. However, by using this process the nanocrystals in the pore walls usually are randomly oriented to each other with respect to the substrate and the mesopores, while it would be desirable to achieve preferred 3D orientation of the crystallites. CVD and molecular beam epitaxy onto single-crystalline substrates are widely used, but suffer from elaborate preparation setups. Solution-processing such as EISA was proposed as a versatile alternative, because of the evident advantages of “beaker” chemistry, but so far required single-crystalline substrates to achieve oriented crystallization. Therefore, it is commonly not expected that films of mesoporous transition metal oxides with a high degree of crystallographic orientation can be formed from aqueous solutions on arbitrary substrates. Here we report a general, straightforward surfactant-mediated methodology for the preparation of well ordered mesoporous films of transition metal oxides with uniaxial crystallographical orientation of the crystals (MoO3, Nb2O5, Ta2O5, V2O5, perovskites) on non-crystalline substrates like glass. In essence, the approach involves dip-coating of polar, wettable substrates (silicon wafers, glass) by an ethanolic solution of a metal oxide precursor (e.g. MoCl5) and polar, organic surfactants such as ionic liquids and amphiphilic block copolymers of the KLE family (poly(ethylene-co-butylene)-b-poly(ethylene oxide)) [1]. Subsequently, the films are heated in air to initiate crystallization, and using the KLE block copolymers leads to ordered mesoporous, crystalline films with a uniaxial crystallographic orientation of the nanocrystals. For instance, in case of MoO3 the [010] planes are orientated parallel to the substrate. A systematic study on various oxides revealed that this effect occurs for oxides with highly anisotropic unit cells (MoO3, etc.), but not for isotropic unit cells (CeO2, SnO2 etc.). The structural anisotropy of these oxides leads to crystallization perpendicular to the lattice planes of maximum polarizability, and the role of the surfactant is to mediate the polarization induced by the surface (“soft epitaxy”) [1]. Furthermore, Lithium insertion experiments revealed that the crystallographic orientation also results in accordingly anisotropic electrochemical properties. We anticipate this approach to provide the basis for the generation of layers of more complex metal oxides. [1] Smarsly et al. Adv. Mater. 2006, 18, 1827.
5:00 PM - **S3.6
Rational Design of Size-Selective Mesoporous Catalysts
Reiner Anwander 1 , Clemens Zapilko 1 , Yucang Liang 1
1 Department of Chemistry, University of Bergen, Bergen Norway
Show AbstractZeolites and related materials like aluminophosphates and periodic mesoporous silicas PMS, mesoporous organosilicas PMO, and mesoporous metal oxides are ubiquitous inorganic porous high-surface-area materials which are widely used as catalyst supports both in industry and academic research. Zeolites and zeotypes are microporous materials (pore diameter < 2 nm) whereas PMSs and PMOs exhibit pore diameters in the range of 2 to 50 nm. Size- or shape-selective reactions are a unique and formidable phenomenon occurring in zeolitic materials. A similar behavior of mesoporous materials has not been observed until now. We herein present a method for the preparation of size-selective mesoporous organic-inorganic hybrid catalysts. Our approach allows the rational design of size-selective catalysts following a simple building blocks principle, which comprises a mesoporous silica with a cagelike pore structure, a silylating reagent and a catalytically active component, which can be a metal compound or an organic group, that is grafted onto the pore walls of the silica. Size selectivity is demonstrated for the Meerwein-Ponndorf-Verley MPV reduction of carbonyl compounds to alcohols.
5:30 PM - S3.7
Evaporation-Induced Self-Assembly of Mesoporous TiO2 Thin Films in Controlled Atmosphere
Catherine Henrist 1 , Natacha Krins 1 , Rudi Cloots 1
1 Chemistry Department, University of Liege, Liege Belgium
Show AbstractThe synthesis of mesoporous oxides in the presence of surfactant mesophases has become very common since the discovery of the silica-based MCM-type materials in the early nineties. However, the low-molecular-weight surfactants used turned out to interact too strongly with transition metal precursors for simply adapting this method to TiO2 synthesis.Recently, block copolymers have been increasingly used to organize mesostructured transition metal oxides, due to the possibility of controlling the interaction between the inorganic and the organic species.Using a PEO-based triblock copolymer surfactant as a template, mesostructured TiO2 was prepared under different experimental conditions. A home-made system was set allowing the dip-coating of a glass substrate into the precursor solution containing the solvent (ethanol), template, titanium alkoxide and acid. The withdrawing of the substrate was performed at a controlled, low speed and under controlled, high relative humidity to favor gentle evaporation of the ethanol-based film. The post-treatment of the film was tuned in an attempt to induce a sufficient condensation of the oxide lattice before the elimination of the template, while avoiding to destroy the ordered mesoporosity.Caracterization techniques used to describe the microstructural and molecular organization of the mesostructured films include thin film X-ray diffraction, infra-red spectroscopy, thermal analysis, scanning electron microscopy, transition electron microscopy, solid state MAS-NMR and BET porosity measurements.
5:45 PM - S3.8
High Temperature Ceramics with Hierarchically Ordered Pore Structure.
Marleen Kamperman 1 , Robert Weissgraeber 1 , Raluca Scarlat 1 , Ulrich Wiesner 1
1 Materials Science & Engineering, Cornell University, Ithaca, New York, United States
Show AbstractHierarchically ordered high-temperature ceramics offer great promise in structural applications, because of their excellent thermal stability and mechanical properties in combination with a high surface area and low flow resistance. We developed an easily controlled bottom-up approach towards hierarchically ordered high-temperature ceramics structured on multiple length scales: ~1000 nm, ~100 nm and ~10 nm. Structuring is obtained by combining latex sphere templating and cooperative assembly of a polysilazane and an amphiphilic block copolymer. Relatively large micron-sized latex spheres self-assemble into an ordered lattice and smaller latex nanospheres are forced to pack closely at the interstices between the micron-spheres. This template is infiltrated with a ceramic precursor/ block copolymer solution, which assembles into nanostructured morphologies that can be permanently set by crosslinking the polysilazane. Subsequent removal of the organic material by calcination leaves a three-dimensionally interconnected, hierarchically ordered, high-temperature ceramic material. Implications of these findings for various applications will be discussed.
Symposium Organizers
Masashi Kawasaki Tohoku University
Jochen Mannhart University of Augsburg
Ramamoorthy Ramesh University of California-Berkeley
Darrell G. Schlom The Pennsylvania State University
L9: Magnetism at Interfaces
Session Chairs
Paul Fuoss
Jacobo Santamaria
Thursday PM, April 12, 2007
Room 3011 (Moscone West)
9:00 AM - **S2.1
Nanocomposites for Application in Organic Electronics
Sundarraj Sudhakar 1 , Mee Yoon Lo 1 , Thomas Kietzke 1 , Changgua Zhen 1 , Ghassan Jabbour 3 , Henk Bolink 2 , Alan Sellinger 1
1 , Institute of Materials Research and Engineering, (IMRE), Singapore Singapore, 3 Chemical and Materials Engineering, Arizona State University, Tempe, Arizona, United States, 2 Instituto de Ciencia Molecular, Universidad de Valencia, Valencia Spain
Show AbstractThis work will describe our recent results in the area of solution processed nanocomposite materials for application in organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs). For example, fluorescent monodisperse derivatives of octavinylsilsesquioxane and hexachloro cyclicphosphazenes have been used as both hole transport and emissive layers in un-optimized OLED architectures to provide efficiencies and brightness levels exceeding 8 cd/A and 35,000 cd/m2 respectively. When strategically functionalized with phosphorescent based emitting moieties, efficiencies exceeding 48 cd/A can be achieved with similar brightness levels as described above. In the area of OPVs, our interest is in finding replacement accepting materials for fullerene derivatives. In this regard, we have synthesized novel materials based on 2-vinyl-4,5-dicyanoimidazoles in high yield from straightforward chemistry. Initial simple solution processed OPV devices prepared using these accepting materials with selected donor polymers provide devices with power efficiencies and open circuit voltages (Voc) exceeding 0.5% and 1.0V respectively.
9:30 AM - **S2.2
Periodic Mesoporous Organosilicas (PMOs): Past, Present, and Future
Michael Froeba 1 , Frank Hoffmann 1 , Maximilian Cornelius 1 , Juergen Morell 1 , Vivian Rebbin 1
1 Institute of Inorganic and Analytical Chemistry, Justus Liebig University Giessen, Giessen Germany
Show AbstractPeriodic mesoporous organosilicas (PMOs) represent a new class of organic-inorganic hybrid materials suitable for a broad range of applications such as chromatography, catalysis, sensing and microelectronics. Unlike in organic functionalized mesoporous silica phases obtained via grafting or co-condensation procedures the organic groups in PMOs are direct parts of the 3D framework structure, thus giving raise to enormous possibilities to tune their chemical and physical properties in designated ways by varying the structure of the precursors. In this presentation the distinctive features of PMOs are discussed, the latest developments concerning compositions, structures, morphologies and potential applications are figured out and finally a brief outlook of future aspects is given.
10:00 AM - **S2.3
Nanostructuring of Hybrid Silica through Self-Assembly and Molecular Recognition.
Michel Wong Chi Man 1 , Guilhem Arrachart 1 , Carole Carcel 1 , Joel Moreau 1 , Christian Bonhomme 2 , Bruno Alonso 4 , Florence Babonneau 2 , Gaelle Creff 3 , Jean-Louis Bantignies 3 , Philippe Dieudonne 3 , Christophe Blanc 3 , Jean-Louis Sauvajol 3
1 Chemistry, LCMCP, Paris France, 2 Chemistry, ENSCM (UMR 5076), Montpellier France, 4 , CRMHT (UMR 4212), Orléans France, 3 , LCVN, Montpellier France
Show Abstract10:30 AM - S2.4
Highly Ordered Hierarchical Silica Hybrid with Controlled Pore Connectivity Based on Adamantylphenol Pore Generators.
Whirang Cho 1 , Bong Jun Cha 2 , Hyung Ik Lee 3 , Ji Man Kim 3 , Kookheon Char 1
1 Chemical Engineering, Seoul National University, Seoul Korea (the Republic of), 2 , KITECH, Cheonan Korea (the Republic of), 3 Department of Chemistiry, Sungkyunkwan University, Suwon Korea (the Republic of)
Show AbstractThe synthesis of inorganic frameworks with specific and organized pore networks has attracted much interest owing to its potential practical promises. Especially introduction of porosity on more than two different length scales as an ordered state with interconnectivity between the pores and hierarchical structure would be advantageous for a variety of applications, such as catalytic supports, adsorbent, electrode material, drug delivery, optics, and electronics. In present study, a direct method to prepare hierarchically ordered mesoporous silica with two different-ranged porous structures from co-condensation of TEOS and porogen-grafted trimethoxysilane in the presence of triblock copolymer Pluronic P123 (EO20PO70EO20), as a structure-directing agent is reported. We designed and synthesized new carbon cage type porogen grafted to poly (methylsilsesquioxane) (PMSSQ), such as 1-(4-trimethoxysilylpropoxyphenyl) adamantane (Adam-grafted SQ) using as a surfactant and silica precursor simultaneously. Adamantylphenol moieties belonging to Adam-grafted SQ, are utilized to serve as template through collective templating of adamantylphenols besides a block copolymer template. Adamantylphenol groups generate additional corrugated intrawall mesopores in addition to larger mesopores confirmed by two-step N2 desorption branch because of pore blocking effect. Also we investigate the effect of preparation conditions, i.e., TEOS/adam-grafted SQ molar ratio in the starting mixture, reaction temperature and aging time for silica condensation, on the ordered hierarchical mesostructure and pore connectivity. Highly ordered hexagonal structure is maintained to the extent that less 15 % of adam-grafted SQ in inorganic sol mixture is used. It is demonstrated that hydrophobic adamantylphenol groups can be located dominantly around PPO core block so far as they fully occupy along the reaction site adjacent to PPO block. As reaction temperature increases, dehydration of PEO corona blocks is also increased and PEO blocks will withdraw themselves into the hydrophobic micellar regions. Subsequently, dehydrated PEO blocks tend to be less stretched in aqueous solvent, which makes it difficult for adamantlyphenol groups to proceed into PPO core block through PEO chains and thus to cluster around PPO block. Also, we found that optimum degree of silica condensation is required to obtain well-defined hierarchical mesostructure by preventing appreciable modification of silica framework during hydrothermal aging step. We have also demonstrated that the presence and location of secondary pores can be controlled by changing chemical linkers connecting between adamantylphenol groups and silane precursors. Current results also show a promise to realize nanoporous thin films with controlled porosity and location of secondary pores.
10:45 AM - S2.5
Self Organized 2D Mesostructured Silica/Semiconducting Polymer Nanocomposite from Non-Aqueous Solution.
Saar Kirmayer 1 , Ekaterina Dovgolevsky 1 , Evgeny Lakin 1 , Michael Kalina 1 , Gitti Frey 1
1 Materials Engineering, Technion - Israel Institute of Technology, Haifa Israel
Show AbstractOrganic-inorganic hybrid materials, offer the opportunity to combine the beneficial properties of both their components, as well as inducing desirable functions unattainable in each individual phase. Mesostructured inorganic hosts incorporated with organic molecular guests, posses the order, orientation, and mechanical and environmental stability of the host, combined with the activity of the guest. However, positioning the organic molecule in the pores of the host during the synthesis is, challenging because organic hydrophobic species are not compatible with the aqueous polar sol-gel process conventionally used in the preparation of ceramic mesostructured hosts. Here we report on the utilization of surfactant self-organization in non-aqueous sol-gel solutions synthesis of highly ordered mesotructured silica incorporated with organic molecules by implementing the Evaporation Induced Self Assembly (EISA) technique. The generality of the new approach is demonstrated by the incorporation of highly hydrophobic, high molecular-weight semiconducting polymers. The optical properties of semiconducting polymer are sensitive to its arrangement and environment, and hence photoluminescence measurements are used as in-situ probes to study the morphology of the confined polymer and its interactions with the host. Depending on the concentration of the surface-active agent, it was possible to prepare 2D hexagonal mesophase silica with conjugated polymer guest species incorporated within the hydrophobic cylinders organized in domains aligned parallel to the substrate surface plane; or a lamellar mesophase silica with the layers oriented parallel to the substrate surface and the conjugated polymer guest species incorporated in the hydrophobic layers, as evident from SAXS, TEM and photoluminescence measurements. A general mechanism for the self-organization of the mesostructured silica-incorporated conjugated polymer films will also be presented.
11:30 AM - **S2.6
Evaporation-Induced Self-Assembly of Porous and Composite Nanostructures.
C. Jeffrey Brinker 1 2 3
1 Regent's Professor, Chemical and Nuclear Engineering, The University of New Mexico, Albuquerque, New Mexico, United States, 2 Regent's Professor, Molecular Genetics and Micro-Biology, The University of New Mexico, Albuquerque, New Mexico, United States, 3 Fellow, Self-Assembled Materials, Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractNature combines hard and soft materials often in hierarchical architectures to get synergistic, optimized properties and combinations of properties with proven, complex functionalities. Emulating such natural material designs in robust engineering materials using efficient processing approaches amenable to manufacturing represents a fundamental challenge to materials scientists and engineers. Currently there is considerable interest in evaporation-driven self-assembly as a means to create porous and composite thin film nanostructures using simple commercial procedures like dip or spin-coating and ink-jet printing. This presentation will first review recent progress on evaporation-induced silica/surfactant self-assembly (EISA) to prepare porous thin film nanostructures of interest for membranes, sensors, and low k dielectrics. Starting with a homogenous solution of surfactant plus hydrophilic oligosilicic acid precursors, solvent evaporation concentrates the depositing film in precursors and surfactant inducing micelle self-assembly and further self-organization into thin film silica/surfactant mesophases. Exploiting the steady, continuous nature of dip-coating, it is possible to spatially resolve the complete evaporation-induced self-assembly pathway (in the coating direction) and interrogate it using spectroscopy and/or grazing incidence SAXS. I will then discuss surfactant self-assembly as a means to organize simultaneously multiple precursors into hybrid (organic/silica or metal/silica) nanocomposites that are optically or chemically polymerizable, patternable, or adjustable. For example, the co-self-assembly of amphiphilic photoacid generators with silica precursors results in photosensitive thin film mesophases in which the pore size, pore volume, surface area, and refractive index may be continuously varied over a range depending on the UV exposure time. Incorporation of switchable, hydrogel or azobenze moieties provides a means to create nanostructures exhibiting chemo-, thermo- or opto-mechanical actuation. Finally biocompatible self-assembly, using phospholipids as the structure-directing agents, allows cell immobilization in a robust self-contained, self-sustaining environment of interest for stand-alone cell-based sensors. When incorporating single-celled organisms, we observe that cells co-opt the EISA process, altering significantly the self-assembly pathway and creating a unique bio/nano interface that maintains cell viability and accessibility upon exposure to harsh desiccating conditions. 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.
L7: Ferroelectrics and Multiferroics
Session Chairs
Lane Martin
Gerhard Meijer
Thursday PM, April 12, 2007
Room 3011 (Moscone West)
12:00 PM - L11.1
Thin-Film Nanocalorimetry: A New Tool for the Study of Oxide Interfacial Reactions.
Lawrence Cook 1 , Richard Cavicchi 1 , Peter Schenck 1 , Mark Vaudin 1 , Winnie Wong-Ng 1 , Makato Otani 1 , Christopher Montgomery 1 , Nabil Bassim 1 , Martin Green 1
1 , NIST, Gaithersburg, Maryland, United States
Show AbstractL9: Magnetism at Interfaces
Session Chairs
Paul Fuoss
Jacobo Santamaria
Thursday PM, April 12, 2007
Room 3011 (Moscone West)
12:00 PM - **S2.7
From Inorganic Metal Oxide to Hybrid Thin Films Prepared via Evaporation Induced Self Assembly (EISA): Synthesis, Characterization and Applications.
Cedric Boissiere 1 3 , David Grosso 1 3 , Lionel Nicole 1 3 , Alida Quach 1 3 , Monika Kuemmel 1 3 , Dominique Rebiere 2 , Clement Sanchez 1 3
1 LCMCP, UPMC, Paris France, 3 , CNRS, Paris France, 2 , Universite Bordeaux I, Bordeaux France
Show AbstractL7: Ferroelectrics and Multiferroics
Session Chairs
Lane Martin
Gerhard Meijer
Thursday PM, April 12, 2007
Room 3011 (Moscone West)
12:15 PM - L11.2
Effects of Strain Relaxation on the Local Structure and Properties in BiFeO3 (001) Thin Films.
Rebecca Sichel 1 , Alexei Grigoriev 1 , Dal-Hyun Do 1 , Rasmi Das 1 , Dong Min Kim 1 , Seung-Hyub Baek 1 , Daniel Ortiz 1 , Zhonghou Cai 2 , Chang-Beom Eom 1 , Paul Evans 1
1 Materials Science Program, University of Wisconsin, Madison, Madison, Wisconsin, United States, 2 , Advanced Photon Source, Argonne National Labs, Argonne, Illinois, United States
Show AbstractStripe domains in ferroelectric thin films form in order to minimize the total energy of the film. It has been known for some time that a stable configuration is reached when the decrease in elastic energy from domain formation is balanced by the energetic costs of domain wall formation, local elastic strains in the substrate, and internal electric field formation from domain polarizations. The size and strain of each domain is determined by the lattice mismatch and the energetic costs of interface formation. Recent piezoelectric force microscopy measurements have shown that BiFeO3 (BFO) films on SrRuO3/SrTiO3 (001) substrates form striped polarization domains. Since the details of the local structure and polarization cannot be measured at the same time with conventional techniques, we have used synchrotron x-ray microdiffraction to study these effects.
Probing only a few domains at a time with the submicron x-ray spot resulted in a diffraction pattern near the substrate (103) reflection consisting of several BFO peaks. We have unambiguously assigned these peaks to individual structural variants. Based on these results, we propose a physical model that includes the striped domains. The structural variants within the stripes are similar to those predicted by striped patterns in rhombohedral films which minimize elastic energy. The local piezoelectric properties were measured using time-resolved microdiffraction in order to examine the role of the striped domains in the linear responses of the film. The out of plane piezoelectric coefficient d
33 was approximately 50 pm/V and the piezoelectric strain was proportional to electric field was up to 0.55%, the maximum strain we have measured. The projection of the in-plane piezoelectric coefficients onto the reciprocal space maps for different structural variants had vastly different values due to the differences in orientation of the domains.
12:30 PM - L11.3
The Growth and Properties of SrRuO3 Thin Films and Heterostructures.
Franklin Wong 1 , Rajesh Chopdekar 1 2 , Yuri Suzuki 1
1 Materials Science and Engineering, University of California, Berkeley, Berkeley, CA, California, United States, 2 Applied Physics and Engineering, Cornell University, Ithaca, New York, United States
Show AbstractSrRuO3 (SRO) is a ferromagnetic conductor that has been studied extensively in terms of its magnetism as well as an electrode material for oxide perovskites. Despite its low Tc of 150K and relatively low spin polarization [1], SRO is an excellent template upon which we can grow oxide heterostructures with interfacial control. We have grown SRO with unit-cell terraces on (001) SrTiO3 (STO) substrates, and observed that the surface quality, microstructure, and magnetization of SRO are strongly dependent on the oxygen pressure of annealing after deposition. High-resolution transmission electron microscopy (HRTEM) has shown that SRO films annealed in reducing environments appear to have oxygen vacancies clustered at grain boundaries of the film, rather than being homogenously distributed. It is possible that vacancy clustering serves as a lattice relaxation mechanism for highly oxygen-deficient SRO films on STO. Long range magnetic order is preserved, but with a suppressed Tc. Furthermore, reduced magnetization may be caused by frustration between the grains at grain boundaries. We have also observed that magnetism and a nearly defect-free structure can be recovered by appropriate annealing in an oxygen ambient. Fully oxygenated SRO films with bulk-like magnetic and transport properties have also been imaged with HRTEM, and they have shown high-quality epitaxy. We have used the atomically terraced SRO surface as a template for the controlled growth of various perovskite thin-film materials, including SrTiO3 (STO), LaAlO3 (LAO), and LaTiOx (LTO). We have synthesized multilayers of SRO/barrier/SRO and SRO/barrier/La0.67Sr0.33MnO3(LSMO) where the barrier is LAO/STO. While the LAO/STO interface have been shown to form confined metallic states through electronic reconstruction [2], others attribute the high interfacial conductivity to oxygen vacancies [3,4]. Sharp interfaces in these heterostructures with few defects have been imaged with HRTEM. LSMO is a colossal magnetoresistive (CMR) conductor that is magnetically softer than SRO, and SQUID magnetometry measurements have shown that the electrodes switch independently in the SRO/barrier/LSMO heterostructure, making it a viable magnetic tunnel junction. Although magnetization of the top and bottom electrodes of the SRO/barrier/SRO structure is not distinguishable, its high interfacial integrity makes it a model system in which to study tunneling through the composite barrier and investigate the effects of localized electronic states within the barrier. [1] D.C. Worledge and T.H. Geballe, Phys. Rev. Lett. 85, 5182 (2000). [2] A. Ohtomo and H.Y. Hwang, Nature 427, 423 (2004).[3] A.S. Kalabukhov, R. Gunnarsson, J. Borjesson, E. Olsson, T. Claeson, and D. Winkler, (2006).[4] W. Siemons, G. Koster, H. Yamamoto, W.A. Harrison, T.H. Geballe, D.H.A. Blank, and M.R. Beasley, (2006).
L9: Magnetism at Interfaces
Session Chairs
Paul Fuoss
Jacobo Santamaria
Thursday PM, April 12, 2007
Room 3011 (Moscone West)
12:30 PM - **S2.8
New Opportunities of Glycol-Modified Precursors in the Synthesis of Highly Porous Materials
Nicola Huesing 1
1 Inorganic Chemistry, Ulm University, Ulm Germany
Show AbstractFor many applications the synthetic chemists seek to copy the properties of natural materials. Porous materials e.g. with a hierarchical organization of the network (as found in almost all biominerals) are desired for a broad variety of applications, including chromatography and catalysis, due to the multiple benefits that arise from each of the pore size regimes. However, despite the drastic progress in the synthesis of porous inorganic materials with control of pore sizes from Ångstrom to micrometers, the preparation of materials with simultaneous tailoring of morphology (monoliths, fibres, etc.) and pore structures on different length scales still remains a challenging task.Hydrolysis and condensation reactions of alkoxysilanes such as tetramethoxy- or tetraethoxysilanes are the “masterkey” reactions in the synthesis of porous silica-based materials. However, the sol-gel process with these precursors is limited in its potential, especially when it comes to the synthesis of mesostructured monolithic materials due to the obligatory presence of the solvent as compatibilizing agent (typically an alcohol) and the catalyst to start the network forming reactions (acid or base). Diol- or polyol- modified silanes such as tetrakis(2-hydroxyethyl)silane or the corresponding titanium analogues as precursors have some distinct advantages since they can be condensed without a co-solvent, under neutral conditions (no catalyst is required to start the sol-gel reactions), and the diols/polyols released upon hydrolysis show a very good compatibility with lyotropic phases of surfactant molecules. In this presentation, the opportunities and the potential opened by the application of diol- or polyol-modified precursors in materials synthesis is discussed. Inorganic and inorganic-organic hybrid porous monoliths (silica and titania-based) prepared by self-assembly processes of the diol- or polyol-modified precursors in the presence of amphiphilic molecules as well as their characterization with respect to structure e.g., by nitrogen sorption, SAXS, XRD, SEM, TEM, etc. and mechanical behavior as well as certain applications is presented.
L7: Ferroelectrics and Multiferroics
Session Chairs
Lane Martin
Gerhard Meijer
Thursday PM, April 12, 2007
Room 3011 (Moscone West)
12:45 PM - L11.4
Low Energy Excitations in Cuprate Superconducting Superlattices and in BaCuO2+x and CaCuO2 Constituent Blocks: Disentangling the Role of Conduction Planes and Charge Reservoirs.
Carmela Aruta 1 , Francesca Fracassi 2 , Giacomo Ghiringhelli 2 , Claudia Dallera 2 , Pier Gianni Medaglia 3 , Antonello Tebano 3 , Nicholas Brookes 4 , Lucio Braicovich 2 , Giuseppe Balestrino 3
1 , CNR-INFM Coherentia, Napoli Italy, 2 CNR-INFM and Dip. di Fisica, Politecnico di Milano, Milano Italy, 3 CNR-INFM Coherentia and Dip. Ingegneria Meccanica, Università Tor Vergata, Roma Italy, 4 , European Synchrotron Radiation Facility, Grenoble France
Show AbstractL8: Microscopy
Session Chairs
Jeff Eastman
Hanns-Ulrich Habermeier
Thursday PM, April 12, 2007
Room 3011 (Moscone West)
9:00 PM - L6.1
Functionalizing γ-AlOOH Surface with Silanol- an Ab-initio Study.
Petri Lehtinen 1 , Alexander Blumenau 1 , Guido Grundmeier 1
1 Interface Chemistry and Surface Engineering, Max Planck Institute für Eisenforschung Gmbh, Düsseldorf, NRW, Germany
Show AbstractHot dip galvanised steel is coated with a ZnA-alloy coating for advanced corrosion protection. The Al-content leads to the formation of 2-3 nm thick Al-oxyhydroxide layers on the alloy surface. The structure of these passive films is very similar to amorphous boehmite. Since the oxide covered metal surface is in most cases either organically coated or adhesively bonded, the formed oxides play an important role in the adhesion of the polymer/oxide/metal composite. Adhesion promotion on the oxide is often performed by the adsorption of bi-functional organosilanes. The silanol groups form quite stable bonds to hydroxyl covered oxides. However, so far little is known on the detailed bonding mechanism.We present theoretical ab-initio results of adsorption of water and silanol molecules on the γ-AlOOH (0001)-surface. Since the experimental adsorption of the silanol on the boehmite surface is done in environments with finite water activities, the adsorption process is therefore a competing process. We will also present some result of adsorption of silanol in the presence of water molecules to achieve an understanding of this process.
9:00 PM - L6.10
Influence of Sublayer Thickness on Magnetic Properties of BaTiO3/CoFe2O4 Multi-layer Thin Films
Ruei-jer Lin 1 , Tai-Bor Wu 1
1 Material Science and Engineering, National Tsing-hua University, Hsinchu Taiwan
Show AbstractBaTiO3/CoFe2O4 multi-layer thin films with different stacking periods were fabricated on Si substrate by dual-cathode RF sputtering system, which is equipped with programmable shutters to precisely control the sublayer thickness. The crystalline structures of the films were studied by XRD. The M-H curves at room temperature were measured by SQUID, and the magnetic domain image was directly observed by magnetic force microscopy(MFM). At a fixed total thickness, with increasing of the period thickness of the CoFe2O4 sublayer, the larger magnetic domains were observed, resulting in the larger saturation magnetization and coercivity. The correlations between the magnetic properties and the ferroelectric/ferromagnetic oxide interfaces were investigated.
9:00 PM - L6.11
Polymer-assisted Deposition of Epitaxial SrRuO3 Thin Films.
Hongmei Luo 1 , Menka Jain 1 , Raymond Depaula 1 , Thomas McCleskey 2 , Anthony Burrell 2 , Quanxi Jia 1
1 Superconductivity Technology Center, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 Materials Chemistry, Materials Physics and Applications Division , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show Abstract9:00 PM - L6.12
Epitaxial Stabilization of YTiO3 Thin Ffilm and Its Physical Properties.
Chang Uk Jung 1 , Seung Chul Chae 2 , Young Jun Chang 2 , Sung Seok A. Seo 2 , Seung Yup Jang 2 , Tae Won Noh 2 , Dong Wook Kim 3
1 Department of Physics , Hankuk University of Foreign Studies, Yongin, Kyounggi-Do, Korea (the Republic of), 2 ReCOE & FPRD, School of Physics and Astronomy, Seoul National University, Seoul Korea (the Republic of), 3 Department of Applied Physics, Hanyang University, Ansan, Gyunggi-do, Korea (the Republic of)
Show Abstract9:00 PM - L6.13
Influence of Interfacial Dislocations on Coercive Fields in Ferroelectric Films.
Yulan Li 1 2 , Shenyang Hu 3 , Michael Baskes 3 , Samrat Choudhury 2 , Darrell Schlom 2 , Turab Lookman 4 , Quanxi Jia 1 , Long-Qing Chen 2
1 , MPA-STC, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 Department of Materials Science and Engineering, The Pennsylvania State University, State College, Pennsylvania, United States, 3 , MST-8, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 4 , T-11, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show Abstract9:00 PM - L6.14
Si:SrTiO3 Interface and its Influence on SrTiO3 as a Buffer Layer for Perovskite Oxide Heteroepitaxy.
Grace Yong 1 , Rajeswari Kolagani 1 , Yong Liang 2 , Rajeh Mundle 3 , Katie Walker 1 , Sanjay Adhikari 1 , Anthony Davidson 1 , David Schaefer 1 , Stephan Friedrich 4
1 Physics, Astronomy & Geosciences, Towson University, Towson, Maryland, United States, 2 Physical Science Research Labs, Motorola Labs, Tempe, Arizona, United States, 3 Center for Materials Research, Norfolk State University, Norfolk, Virginia, United States, 4 Advanced Detector Group, Lawrence Livermore National Lab, Livermore, California, United States
Show AbstractIn addition to potential application as a gate oxide, there is growing interest in SrTiO3 (STO) on Silicon, as a chemical buffer and structural template for the subsequent heteroepitaxy of other electronically active perovskite oxides. We are growing epitaxial thin films of Nd0.67Sr0.33MnO3 (NSMO), by Pulsed Laser Deposition (PLD), on STO buffered Si. The STO buffer layer, 6 to 10 nm thick, is grown by MBE. An additional template layer of Bi4Ti3O12 (BTO), underlying the NSMO layer, is used to improve the NSMO film quality by facilitating better lattice match. We will discuss the influence of the STO/Si interface on the structure of the MBE grown STO layer and subsequently on the structure and properties of the BTO and NSMO layers grown on it. Correlation of the structure and quality of the interface with the properties of the overlayers will be presented, using a combination of transmission electron microscopy, atomic force microscopy, high resolution x-ray diffraction, and electrical transport measurements.
9:00 PM - L6.15
Plasmon Enhancement of Photoinduced Resistivity Changes in Bi1-xCaxMnO3 Thin Films
Vera Smolyaninova 1 , Elena Talanova 1 , Rajeswari Kolagani 1 , G. Yong 1 , R. Kennedy 1 , M. Steger 1 , K. Wall 1
1 Dept. of Physics, Astronomy and Geosciences, Towson University, Towson, Maryland, United States
Show AbstractDoped rare-earth manganese oxides (manganites) exhibit a wide variety of physical phenomena due to complex interplay of electronic, magnetic, orbital, and structural degrees of freedom and their sensitivity to external fields. A photoinduced insulator to conductor transition in charge-ordered (CO) manganites is especially interesting from the point of view of creating photonic devices. Thin films of Bi0.4Ca0.6MnO3 exhibit large photoinduced resistivity changes associated with melting of the charge ordering by visible light [1]. Photoinduced effects are much larger in thinner films, which could be an indication of larger sensitivity of the surface to the external fields. We have found a considerable increase of the photoinduced resistivity changes in the Bi0.4Ca0.6MnO3 thin film after depositing metal nanoparticles on the surface. This increase can be explained by enhancement of local electromagnetic field at the interface between the film and the metal nanoparticle due to the plasmon resonance. The changes in lifetime of the photoinduced state will be reported, and the possible origin of these effects will be discussed. [1] V. N. Smolyaninova at al., Appl. Phys. Lett. 86, 071922 (2005).
9:00 PM - L6.16
ZnO (0001) Equilibrium Surface Structure in Controlled Environments.
Jeffrey Eastman 1 , Dillon Fong 1 , Paul Fuoss 1 , Peter Baldo 1 , Guangwen Zhou 1 , Loren Thompson 1
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States
Show Abstract9:00 PM - L6.17
Ir/Au Ohmic Contacts on Bulk, Single-Crystal n-type ZnO.
Jon Wright 1 , R. Khanna 1 , L. Stafford 1 , B. Gila 1 , D. Norton 1 , S. Pearton 1 , F. Ren 2 , I. Kravchenko 3
1 Materials Science and Eng., The University of Florida, Gainesville, Florida, United States, 2 Chemical Engineering, University of Florida, Gainesville, Florida, United States, 3 Physics, University of Florida, Gainesville, Florida, United States
Show AbstractThe contact characteristics on bulk single-crystal n-type ZnO of an Ir/Au metallization scheme deposited by sputtering are reported as a function of annealing temperature in the range 200-1000°C (N2 ambient). The contacts exhibited Ohmic behavior for all temperatures and show a minimum specific contact resistivity of 3.6x10-5 Ω.cm2 after a 1000°C anneal. The contacts transition to rectifying behavior after annealing above 1100°C, coincident with a degraded surface morphology including agglomeration of Ir to the surface and heavy intermixing of the Ir and Au. The Ir contacts exhibit higher thermal stability but poorer specific contact resistivity than conventional Ti/Au metal stacks on bulk n-type ZnO. The contacts showed very little change in resistance after extended aging (30 days) at 350°C. Annealing under O2 ambient led to an increase in contact resistivity by orders of magnitude.
9:00 PM - L6.18
Analytical Transmission Electron Microscopy Study on the Oxygen Defect Formation of Ti Oxide Thin Films Sandwiched between Al Electrodes.
Hu Young Jeong 1 2 , Min Ki Ryu 2 , Sung-Yool Choi 2 , Jeong Yong Lee 1
1 Materials Science and Engineering, KAIST, Daejeon Korea (the Republic of), 2 Nano-Bio-Electronic Devices Team, ETRI, Daejeon Korea (the Republic of)
Show AbstractResistive RAM (ReRAM) using bistable switching of binary oxides such as Nb2O5, ZrO2, TiO2 and NiO has been one of the promising candidates for the next-generation nonvolatile memories. We reported the electrical conductivity switching behaviors of Ti oxide thin film memory devices and suggested this conduction mechanism could be associated with the trap-controlled space-charge-limited-current of the trap sites in the oxide films. To confirm this mechanism, two elemental analyses, energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS), were applied to Al/TiOx/Al. The Ti oxide thin film layer with a thickness of ~10nm was deposited by a plasma-enhanced atomic layer deposition (PEALD) method between Al electrodes. For the observation of the chemical composition and elemental concentration profiles in the Ti oxide layer and interfaces with Al electrodes, an EDS line scan was performed across the specimen using field-emission scanning transmission electron microscope (JEM 2100F) with 0.5nm probe size. Oxygen line profiles show the oxygen concentration in Ti oxide layer around top Al electrode is more deficient. This asymmetric structure is well consistent with the electrical I-V characteristics. For the more evidence, an electron energy loss spectroscopy (EELS) analysis was carried out with a spatial resolution of ~1nm equipped in the JEM ARM 1300S (1.25MeV, point resolution 1.2Å). The oxygen EELS mapping data clearly show the oxygen distribution in Ti oxide layer is inhomogeneous and the top region is more deficient than bottom region. Based on the two elemental TEM analyses, it is demonstrated that the origin of trap sites in the Ti oxide thin films is the oxygen defects, caused by the oxygen diffusion process at the interface between the Ti oxide layer and the top Al electrode.
9:00 PM - L6.19
Fabrication of Multi-oxides Thin Film on Iron-base Metal by Laser Color Marking Technique.
Seisuke Kano 1 , Tadatake Sato 3 , Tomoyuki Togashi 2 , Kaoru Itagaki 2 , Hiroyuki Niino 3 , Hirofumi Shimura 1
1 Advanced Manufacturing RI, Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan, 3 Photonics RI, Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan, 2 , Itagaki Metal, Sanjo, Niigata, Japan
Show Abstract9:00 PM - L6.2
Improvement of Turn-off Characteristics in ZnO TFT's by Introducing Hydrogen During MOCVD Growth.
Jungyol Jo 1 , Ogweon Seo 2 , Hyoshik Choi 1 , Chan Bong Jun 2
1 Electrical and Computer Engineering, Ajou University, Suwon Korea (the Republic of), 2 NFC, Samsung Advanced Institute of Technology, Suwon Korea (the Republic of)
Show AbstractZnO generally shows n-type characteristics due to defects. The high electron concentration is an obstacle for thin-film transistor (TFT) application, and it is necessary to control carrier concentration by reducing defects. We used metalorganic chemical vapor deposition (MOCVD) to grow ZnO. The purpose of our study is to realize high quality ZnO TFT by MOCVD. Our initial measurements of x-ray photoelectron spectroscopy (XPS) showed that the ratio of Zn:O is ~ 55:45. It appears that the defects induced by the extra Zn will affect performance of ZnO TFT’s. In order to solve this problem, we introduced hydrogen (H2) during growth. We hoped that the additional H2 would passivate the defects. With this method, we could obtain high quality ZnO TFT’s with 107 on/off ratio and 12 cm2/Vsec mobility.Our MOCVD system has a horizontal reactor operating at atmospheric pressure. DEZ and O2 were used as sources for Zn and O. N2 was employed as a carrier gas with flow rate of 2000 cc/min, and H2 of 300 cc/min flow rate was added. O2 (160 cc/min) and DEZ were designed to meet at 2 cm before the substrate. ZnO films were grown on n-type Si substrates with a thermal oxide of 110 nm thickness. The ZnO film thickness is around 50 nm. Growth temperature was varied between 200oC to 500oC. Measurements of secondary ion mass spectroscopy (SIMS), x-ray diffraction (XRD), and photoluminescence (PL) showed reasonable film quality. They showed that crystal quality improves as growth temperature is increased from 200oC to 500oC. SIMS results show that our ZnO films have significant amount of C and H, even without the additional H2. More C and H were incorporated into the film at lower growth temperature.Our ZnO TFT’s were fabricated by evaporating Al through shadow masks. TFT channel has 15 μm length and 500 μm width. Current-voltage data of ZnO TFT grown at 250oC showed 12 cm2/Vsec mobility and 107 on/off ratio, with -5V threshold voltage. Without H2 flow, on/off ratio of our TFT was very poor. Our results give some answer for the role of hydrogen. In our case, we observed that higher hydrogen concentration (grown at lower temperature) improves mobility. This result is in contradiction with general case where higher growth temperature improves mobility. Our result suggests that in MOCVD grown ZnO, crystal quality is not a main factor in determining TFT characteristics. The higher mobility in 250oC grown sample is due to defect passivation by the higher hydrogen concentration.In summary, we demonstrated that high quality ZnO films can be grown by MOCVD at temperature as low as 250oC, with help of additional H2. SIMS measurement suggests that hydrogen incorporated during MOCVD growth is responsible for the improvements of mobility and turn-off characteristic, through passivation of defects. With this method, we could obtain ZnO TFT’s with 107 on/off ratio and 12 cm2/Vsec mobility.The work at Ajou University was supported by CDA Co., Ltd.
9:00 PM - L6.21
Electron Microscopy Studies of Manganites Thin Films Grown on Terraced Substrates.
Mauro Porcu 1 , Jan Aarts 2 , Christianne Beekman 2 , Henny Zandbergen 1
1 National Centre for High Resolution Electron Microscopy, Delft Technical University, Delft Netherlands, 2 Kamerlingh Onnes Laboratory, Leiden University, Leiden Netherlands
Show Abstract9:00 PM - L6.22
Distinguishing Strain and Interface Effects on the properties of Epitaxial Manganite Thin Films.
Anthony Davidson 1 , Rajeswari Kolagani 1 , Grace Yong 1 , Vera Smolyaninova 1 , Elena Talanova 1 , David Schaefer 1 , Elissaveta Bacharova 1
1 Physics, Astronomy& Geosciences, Towson University, Towson, Maryland, United States
Show AbstractProperties of ultra thin films (<10 nm) of CMR manganite materials have been known to be remarkably different from those of thicker films or bulk materials. Below a critical thickness, insulator-metal transition is suppressed for films on lattice-mismatched substrates. Application of strong magnetic fields have been known to induce insulator-metal transition in such strained films at low temperatures. These effects, which are strongly substrate dependent,have been largely attributed to the role of bi-axial lattice mismatch strain. Our recent results of epitaxial thin films of La0.67Ca0.33MnO3 thin films on two substrates with varying degrees of compressive lattice mismatch indicate that the properties of ultra thin films are influenced by the nature of the film-substrate interface, in addition to the effect of lattice mismatch strain. Interestingly, the suppression of the insulator-metal transition is less in films on the substrate with the larger lattice mismatch, contrary to what would be expected from strain effects alone. We will present results correlating the electrical and magneto transport properties with the structure and film morphology. These results clearly differentiate the effects of lattice mismatch strain and those of defects and interfaces. We will also discuss the effect of surface treatment of the substrates that alter the interface characteristics.
9:00 PM - L6.23
Effect of Processing Conditions on Electrical and Magnetic Properties of Pb(Zr,Ti)O3 -CoFe2O4 Multilayers Thin Films
Nora Ortega 1 , N. Baskaran 1 , P. Bhattacharya 1 , Ram Katiyar 1 , P. Dutta 2 , M. Seehra 2 , Ichiro Takeuchi 3 , S. Majumder 4
1 Physics, University of PUerto Rico, San Juan, Puerto Rico, United States, 2 Physics, West Virginia University, Morgantown, West Virginia, United States, 3 Department of Materials Science and Engineering, University of Maryland, College Park, Maryland, United States, 4 Materials Science Center, Indian Institute of Technology, Kharagpur India
Show AbstractMultiferroics, which display simultaneous magnetic, electric and ferroelasticity ordering, have drawn increasing interest due to their functionality for a variety of device applications. Since, only few materials exhibit this kind of properties, intensive research activity is being pursued towards the development of new materials with strong magneto-electric (ME) coupling. In this work we have fabricated ferroelectric (FE) Pb(Zr,Ti)O3 (PZT) and ferromagnetic (FM) CoFe2O4 (CFO) multilayers with 3, 5, and 9 layers of the configuration PZT/CFO (PC) and CFO/PZT (CP) by pulsed laser deposition technique. The films were deposited at 400 °C and post annealed to 650 °C using rapid thermal annealing. We have investigated the effect of reversing the order of FE and FM layer in the multilayers configuration and the post annealing time (75, 150 and 300 s) on the resulting electrical/magnetic properties. The x-ray diffraction and Raman spectra of these multilayers revealed that the perovskite PZT and the spinel (CFO) were grown as two separate phases. The TEM and XPS depth profile of the films showed that the layer structure was not clear, more inter-diffusion of the CFO and PZT was observed when both the number of layers and annealing time were increased. The dielectric constant (εr) of PC multilayers showed strong frequency dispersion. Similar behavior of εr of CP multilayers structure was observed. Reversing the multilayer configuration from CP to PC resulted in increasing the remanent polarization (Pr). Furthermore, the increase in the post-annealing time of the multilayers also increased both εr and Pr remarkably. The ac impedance data of the multilayers were modeled by considering the multilayer system consisting of the 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. The ME effect of the multilayer films will be discussed.
9:00 PM - L6.24
Thin Equilibrium Amorphous Films at Metal-Oxide Interfaces.
Wayne Kaplan 1 , Mor Baram 1
1 Department of Materials Engineering, Technion - Israel Institute of Technology, Haifa Israel
Show AbstractThe existence of nanometer-thick amorphous equilibrium films at metal-ceramic interfaces has been experimentally verified for the Au-Al2O3 system. The films were formed using a novel experimental approach, in which thin sputtered films of Au were dewetted on a sapphire substrate which was previously partially wetted with drops of anorthite glass (CaO-2SiO2-Al2O3). The process resulted in equilibrated metal particles residing on glass drops and on the sapphire substrate adjacent to the glass drops. The metal particles which formed on the glass drops ‘sank’ through the glass and reached the interface with the substrates. Aberration corrected transmission electron microscopy and analytical transmission electron microscopy were used to confirm the existence of the ~1nm thick amorphous films at the metal particle substrate interfaces. In addition, positive and relatively large Hamaker constants were calculated for the Au-film-Al2O3 interface, which indicates the existence of a stabilizing attractive van der Waals force, similar to equilibrium films at grain boundaries in ceramics. Adjacent to the glass drops, a ~1nm thick surficial film was also detected on the (0001) surface of sapphire substrates partially wetted by anorthite glass. The refractive index required to stabilize the surface films, via a positive Hamaker constant, is explored through changes in the film composition.
9:00 PM - L6.25
AFM Study of m-plane Al2O3 Surface Reconstruction.
Jessica Riesterer 1 , Shelley Gilliss 1 , N. Ravishankar 1 2 , C. Carter 1
1 Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota, United States, 2 Materials Science Centre, Indian Institute of Science, Bangalore India
Show AbstractSapphire wafers that are used as substrate materials are typically cut and polished by a commercial material supplier. This treatment results in a damaged surface layer and encourages the surface plane to reconstruct into a more energetically favorable crystallography via a faceting process. However, how this faceting actually occurs is not well understood. For all crystalline materials, high-energy crystallographic planes are able to reconstruct into faceted surface structures with a lower total surface energy even if the actual surface area increases. Beginning with a single facet, nucleation, growth, coalescence and migration of facets may occur when the material surface is exposed to elevated temperatures. The study reported here emphasizes the mechanism of this reconstruction process by following individual alumina (α-Al2O3) facets from the initial nucleation until significant surface coarsening has occurred. The as-received m-plane (10-10) alumina surface is marked with a grid of indentations using a gravity-loaded hardness tester. Using these indentations as a reference area, the same region of the bulk specimen may then be repeatedly examined after each step in a sequence of heat treatments. Sapphire samples are annealed at 1400°C in air for varying lengths of time followed by a thermal quench in air. Contact-mode atomic-force microscopy (AFM) is used to monitor the reconstruction after each treatment. The m-plane of alumina is found to reconstruct into a hill-and-valley morphology comprising of “simple” and “complex” surface facets; facet nucleation occurs on the complex surface if facet growth does not occur. The indentations that are used as fiducial markers may accelerate facet growth and may contribute to crystal growth if too close to the region of interest. Healing of surface indentations is also being monitored.
9:00 PM - L6.26
Role of the SiO2-Si interface on the thermally activated metallic-to-insulator transition observed in FeSi and CoSi films on Si substrates.
Sarath Witanachchi 1 , Houssam Abou-Mourad 1 , Hasitha Weerasingha 1 , Pritish Mukherjee 1
1 Department of Physics, University of South Florida, Tampa, Florida, United States
Show AbstractThin films of FeSi, CoSi, and TiSi deposited on insulating substrates show a gradual increase of resistance with decreasing temperature. When the films were deposited on doped silicon substrates with the intact native SiO2 layer, both FeSi and CoSi films showed a metallic behavior near room temperature, that resembled the conductivity of the doped Si substrate, followed by a metal-like to insulator-like transition of more than three orders of magnitude change in resistance around 260 K. The transition was absent in TiSi films. The current-voltage characteristics before the transitions were linear while after the transition they became highly nonlinear. This result suggests that the FeSi and CoSi films make ohmic contacts with Si across the SiO2 layer at high temperature. These observations are consistent with a transport mechanism where the current percolation path is switched from substrate to the film near the transition temperature due to a rapid increase in the interfacial resistance. Our experiments with discontinuous films rule out the conduction through an inversion layer at the Si-SiO2 interface as a possible mechanism. The experimental results agree well with a three-layer model that incorporates an exponentially increasing interfacial resistance. Cross-sectional TEM analysis indicated diffusion of Fe through the oxide barrier and accumulation of Fe and Co at the SiO2/Si interface. We attribute this effect to the formation of interface states by multi-valet transition metal ions that diffuse to the Si-SiO2 interface. These states alter the band bending at the Si-SiO2 interface giving rise to an ohmic contact. With decreasing temperature the magnetic interaction between the transition metal ions cause the electrons at the interface states to be localized, leading to a rapid increase in resistance. The absence of a transition in TiSi films, where Ti+4 is a nonmagnetic ion, supports this conclusion. Application of a magnetic field altered the transition characteristics giving rise to a more than 40% magnetoresistance near the transition temperature. The dependence of the magnetic field direction on magnetoresistance will be presented.
9:00 PM - L6.27
Effect of Ferroelectricity on Electron Transport in Pt/BaTiO3/Pt Tunnel Junctions.
Julian Velev 1 , Chun-Gang Duan 1 , Kirill Belashchenko 1 , Sitaram Jaswal 1 , Evgeny Tsymbal 1
1 Department of Physics, University of Nebraska, Lincoln, Nebraska, United States
Show AbstractIn the past decade the phenomena of electron tunneling and ferroelectricity have attracted significant interest due their to potential applications in thin-film electronic devices such as magnetic tunnel junctions (electron tunneling) and non-volatile ferroelectric memories (ferroelectricity). Recently, driven by demonstrations of ferroelectricity in ultrathin films, the idea to comibine these two phenomena in a unique electronic device utilizing a ferroelectric barrier in a tunnel junction was proposed [1]. In this work we use first-principles electronic structure and transport calculations to demonstrate the impact of the electric polarization on electron transport in ferroelectric tunnel junction (FTJ). Using a Pt/BaTiO3/Pt FTJ as a model system, we show that the polarization of the BaTiO3 barrier leads to the substantial drop in the tunneling conductance, as compared to non-polarized barrier, due to the change in the electronic structure driven by ferroelectric displacements. We find a sizable change in the transmission probability across the Pt/BaTiO3 interface with polarization reversal. These results reveal exciting prospects that FTJs offer as resistive switches in nanoscale electronic devices. Supported by NSF-MRSEC.[1] E. Y. Tsymbal and H. Kohlstedt, Tunneling across a ferroelectric, Science 313, 181-183 (2006).
9:00 PM - L6.28
Characterizing Grain Boundary Migration and Grain Growth.
Jessica Riesterer 1 , Jeffrey Farrer 2 , N. Ravishankar 1 3 , C. Carter 1
1 Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota, United States, 2 Dept. of Physics and Astronomy, Brigham Young University, Provo, Utah, United States, 3 Materials Science Centre, Indian Institute of Science, Bangalore India
Show AbstractIn spite of the critical role that it plays in the development of texture, grain boundary migration, and the resulting grain growth, is still not well understood. The two most important factors governing grain boundary migration are the chemistry along the interface and mis-orientation between the grains. The driving force for grain growth may be influenced by the surface orientation of grains and by the mis-orientation across the grain boundary. Special mis-orientations may be able to accommodate different impurities. Grain boundaries in ceramics tend to have considerable excess volume relative to the bulk structure that can accommodate large concentrations of impurity atoms. The effect of individual impurity atoms is often not understood and the effects of co-doping are only beginning to be explored systematically. The present study examines the relative importance of surface orientation and grain boundary mis-orientation and how the driving force for migration may be influenced by the presence of a liquid phase during processing. Polycrystalline ceramics have been hot-pressed to form pure polycrystalline bicrystal-type assemblages. A film of glass has been deposited using pulsed-laser deposition (PLD) prior to hot-pressing. A sequence of heat treatments allow the microstructural evolution to be monitored using both imaging and electron backscatter diffraction (EBSD) in the SEM, and then for individual grain boundaries to be examined at higher resolution by other techniques. The effects of changing the chemistry of the grain boundary on its migration, and in particular abnormal grain growth (AGG), will be discussed.
9:00 PM - L6.29
Effects of Interface Pinning on Poling Behaviors of Epitaxial Pb(Mg1/3Nb2/3)O3-PbTiO3/SrRuO3 Heterostructures.
Jihye Lee 1 , Miri Choi 1 , Yoojin Oh 1 , William Jo 1
1 Physics, Ewha Womans University, Seoul Korea (the Republic of)
Show Abstract9:00 PM - L6.3
Interface Properties of PrxAl2-xO3 (x = 0, 1, 2) High-k Dielectrics on TiN Studied by Synchrotron Radiation X-ray Photoelectron Spectroscopy
Grzegorz Lupina 1 , Thomas Schroeder 1 , Christian Wenger 1 , Jarek Dabrowski 1 , Hans-Joachim Muessig 1
1 , IHP-Microelectronics, Frankfurt/Oder Germany
Show Abstract9:00 PM - L6.30
Lack of Intrinsic Size Effects in the Ferroelectric Properties of Single Crystal Nanocapacitors Made using a Focused Ion Beam
Mohamed Saad 1 , Paul Baxter 1 , Alina Schilling 1 , Tim Adams 1 , Robert Bowman 1 , Marty Gregg 1 , Finlay Morrison 3 , James Scott 2
1 Physics & Astronamy, Queen's University Belfast, Belfast United Kingdom, 3 Chemistry, University of St. Andrews, Fife , Scotland United Kingdom, 2 Symetric Centre for Ferroelectric, University of Cambridge, Cambridge United Kingdom
Show Abstract9:00 PM - L6.31
Effects of Ceramic-Metal Interface Structure and Energetics on Phase Patterning by Constrained Spinodal Decomposition.
Joseph McKeown 1 2 , Joshua Sugar 1 , Velimir Radmilovic 2 , Andreas Glaeser 1 , Ronald Gronsky 1
1 Materials Science & Engineering, UC Berkeley, Berkeley, California, United States, 2 National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show Abstract9:00 PM - L6.32
The Effect of Strain in BZT Thin Films Grown on NB:STO and MgO Substrates
Jennifer Weaver 1 , Zheng Yuan 1 , Jian Liu 1 , Chonglin Chen 1
1 Physics and Astronomy, University of Texas at San Antonio, San Antonio, Texas, United States
Show AbstractBarium strontium titanate (Ba, Sr) TiO3 thin films have currently become very attractive materials for applications in decoupling capacitors, storage capacitors and dielectric field tunable elements for high frequency devices. Ferroelectric Barium Zirconate Titanate (BZT) is a possible alternative to BST in the fabrication of ceramic capacitors because Zr4+ is chemically more stable than Ti4+. The ferroelectric phase transition at the Curie temperature (Tc) in BZT bulk materials is known to change strongly with Zr content. BZT ceramics exhibit a diffuse phase transition and have high tunability in compositions with Zr content of 20% or more. Also unlike the BST, which has three phase transifions, the BZT only has one phase transition from rhombohedral to cubic structure. Based on BZT’s attractive dielectric properties, recently we have deposited BZT thin films on both Nb:STO and MgO substrates by pulsed laser deposition. By means of Rutherford Backscattering (RBS), X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Rammen Spectroscopy, the composition, thickness and crystallinity of the thin films were analyzed, respectively. Using interdigital capacitors(IDC) with Au electrodes on thin films, the dielectric constant and loss tangent were measured as a function of bias electric field and temperature at a broad frequeny range. Our goal is to investigate the effect of the lattice mismatch induced strains on the BZT’s dielectric properties, dielectric loss and its phase transition.
9:00 PM - L6.33
Synthesis of Functionally Porous Silica Nanoparticles for Mercury Removal in Water
Tingying Zeng 1
1 Chemistry, Western Kentucky University, Bowling Green, Kentucky, United States
Show Abstract9:00 PM - L6.34
Growth and Relaxation Mechanisms for (111)-Oriented Ba0.6Sr0.4TiO3 Thin Films Grown on SrTiO3(111) Substrates
Hui Du 1 , Patrick Fisher 1 , Paul Salvador 1 , Marek Skowronski 1 , Oleg Maksimov 2
1 Material science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States, 2 Electro-Optics Center, Pennsylvania State University, Freeport, Pennsylvania, United States
Show Abstract9:00 PM - L6.5
Fabrication of p-n Junction Devices Based on Lanthanum Manganites.
Vasilis Papamakarios 1 , Mark Blamire 1
1 Department of Materials Science, University of Cambridge, Cambridge United Kingdom
Show AbstractMixed-valent manganites have attracted considerable attention since the observation of the colossal magnetoresistance (CMR) effect. More recently, research interest has been focused on the fabrication of artificially layered complex oxide structures, such as p-n junctions for the development of novel functional devices. Compared to p-n junctions based on conventional semiconductors, the ones comprising manganese oxides have not been thoroughly investigated, although the latter may exhibit some very interesting characteristics, considering the strong magnetic and electronic correlation of these oxides.In some of the reported structures, in order to obtain rectifying (or rectifying-like) characteristics, an insulating layer had to be inserted between p- and n-type layers, to reduce tunneling current1 and avoid reaction and diffusion2. However, it is now established that p-n junctions with good rectifying characteristics can still be fabricated, without the need of such an intermediate layer, by just optimising the fabrication conditions and obtaining good crystal quality and clean interfaces3. Electric field modulation of ferromagnetism and the CMR effect have also been reported4,5, making these junctions promising for various applications.Here we present our results from the investigation of p-n junction devices composed of La0.67Sr0.33MnO3 (p-doped) and La0.7Pr0.3MnO6 (n-doped)3 thin films. The films were deposited on SrTiO3 (001) single crystal substrates using the pulsed laser deposition technique. Magnetic and structural characterisation of the samples was carried out using a vibrating sample magnetometer and a high resolution x-ray diffractometer, respectively. The samples were then patterned by using optical lithography, followed by broad Ar ion milling to micron scale wires and associated tracks and contact pads, so that four-point measurements could be performed. These tracks were then processed with a Ga+ focused ion beam system to achieve vertical transport. The I-V characteristics of these junctions in various magnetic fields and temperatures are presented.[1] M. Sugiura, K. Uragou, M. Noda, M. Tachiki, and T. Kobayashi, Jpn. J. Appl. Phys., Part 1 38, 2675 (1999).[2] C. Mitra, P. Raychaudhuri, G. Kobernik, K. Dorr, K.-H. Muller, L. Schultz, and R. Pinto, Appl. Phys. Lett. 79, 2408 (2001).[3] J. Zhang, H. Tanaka, and T. Kawai, Appl. Phys. Lett. 80, 4378 (2002).[4] H. Tanaka, J. Zhang, and T. Kawai, Phys. Rev. Lett. 88, 027204 (2002).[5] H. B. Lu, S. Y. Dai, Z. H. Chen, L. F. Liu, H. Z. Guo, W. F. Xiang, Y. Y. Fei, M. He, Y. L. Zhou, and G. Z. Yang, Chin. Phys. Lett. 20, 137 (2003).[6] P. Duan, Z. Chen, S. Dai, Y. Zhou, H. Lu, K. Jin and B. Cheng, Appl. Phys. Lett. 84, 4741 (2004).
9:00 PM - L6.6
Interface Magnetoelectric Effect.
Chun-Gang Duan 1 , Sitaram Jaswal 1 , Evgeny Tsymbal 1
1 Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska, United States
Show AbstractThe prospect to change magnetic properties of materials by applied electric fields is very promising due to new possible functionalities of electronic devices based on these materials. This phenomenon known as magnetoelectric effect can be significantly enhanced in composite multiferroics such as ferromagnet/ferroelectric multilayers in which the coupling between two different order parameters occurs across the interface. Here using first-principles calculations based on density-functional theory we explore a new magnetoelectric effect in ferroelectric/ferromagnetic multilayers driven by interface bonding [1]. We consider a Fe/BaTiO3(100) multilayer as a representative composite multiferroic to investigate this phenomenon. We find that displacements of atoms caused by ferroelectric instability alter the overlap between atomic orbitals at the interface which affects the interface magnetization. This produces a magnetoelectric effect caused by the change in the interface magnetization induced by the polarization reversal in the ferroelectric under the influence of applied electric field. The predicted magnetoelectric effect is much larger than that observed in bulk materials and opens a new direction to control magnetic properties of thin-film layered structures by electric fields. 1. C.-G. Duan, S. S. Jaswal, and E. Y. Tsymbal, “Predicted magnetoelectric effect in Fe/BaTiO3 multilayers: ferroelectric control of magnetism”, Phys. Rev. Lett. 97, 047201 (2006).
9:00 PM - L6.7
The Microstructures of LaVO3 and YVO3 Thin Films Grown on LaAlO3 and SrTiO3 Substrates.
Miaofang Chi 1 , Lane Martin 2 , Ramamoorthy Ramesh 2 3 4 , Nigel Browning 1 5
1 Department of Chemical Engineering and Materials Science, University of California, Davis, Davis, California, United States, 2 Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, California, United States, 3 Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 4 Department of Physics, University of California, Berkeley, Berkeley, California, United States, 5 Materials Science and Technology Division, Lawrence Livermore National Laboratory, Livermore, California, United States
Show Abstract9:00 PM - L6.8
Fabricated All Transparent(Indium zinc oxide) Inorganic thin film transistor
Jin-Woo Han 1 , Young-Hwan Kim 1 , Byoung-Yong Kim 1 , Jong-Yeon Kim 1 , Dong-Hun Kang 1 , Dae-Shik Seo 1
1 electrical and electronic engineering, Yonsei university, Seoul Korea (the Republic of)
Show Abstract9:00 PM - L6.9
Functional Properties of Copper Oxide for Organic Thin-Film Transistors
JeongWoo Park 1 , Jieun Ghim 1 , Seokju Kang 1 , Kangjun Baeg 1 , Dong-Yu Kim 1
1 Dept. of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju Korea (the Republic of)
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Symposium Organizers
Masashi Kawasaki Tohoku University
Jochen Mannhart University of Augsburg
Ramamoorthy Ramesh University of California-Berkeley
Darrell G. Schlom The Pennsylvania State University
L10: RRAMs
Session Chairs
Andreas Schmehl
Yuri Suzuki
Friday AM, April 13, 2007
Room 3011 (Moscone West)
2:30 PM - **L8.1
Imaging the Surface and Interface Domain Structure of Magnetic and Multiferroic Materials Using X-PEEM
Andreas Scholl 1
1 ALS, LBNL, Berkeley, California, United States
Show AbstractThe interface magnetic structure of ferromagnetic, antiferromagnetic, and multiferroic oxid films controls the functionality of these materials in device applications. Exchange bias is one technologically important application of ferromagnetically and antiferromagnetically ordered materials. Novel multiferroic materials incorporate multiple types of order in the same material, combining for example antiferromagnetic and ferroelectric properties, and promise control of magnetism by charge.X-ray Photoemission Electron Microscopy (X-PEEM) has the unique ability to image surface ferromagnetic and ferroelectric structures at high spatial resolution, both in a ferroic or antiferroic configuration. The surface sensitivity is given by the short mean free path of the emitted secondary electrons of 2-5 nanometers. Current instruments at synchrotron sources such as the Advanced Light Source reach a spatial resolution down to 50-100 nanometers. Next generation microscopes employing aberration correction, which are about to become available, promise to reach single nanometer resolution. Sensitivity to the magnetic, ferroelectric, and electronic structure is achieved using the near edge x-ray absorption fine structure (NEXAFS), x-ray circular, and linear dichroism, XCD and XLD. Utilizing the ~70 picosecond pulses of synchrotron sources, it is possible to go beyond static imaging and directly measure the magnetic and possibly ferroelectric dynamics at nanometer spatial and picosecond temporal resolution [1]. Two examples will be shown that demonstrate the power of the X-PEEM technique: Imaging of antiferromagnetic domain structures has been the key to understanding exchange bias. X-ray magnetic linear dichroism imaging has shown that exchange bias in Co/NiO and Co/LaFeO3 is the result of interface exchange coupling, domain-by-domain, between antiferromagnetic and ferromagnetic domains [2]. It was found that the bias strength scales with the concentration of uncompensated interface spins and is inversely proportional to the domain size [3]. An antiferromagnetic domain wall anchors the surface spins in the bulk of the antiferromagnet. BiFeO3 is a room-temperature ferroelectric antiferromagnet. High-resolution x-ray magnetic linear dichroism images of both antiferromagnetic and ferroelectric domain structures of (001)-oriented multiferroic BiFeO3 films revealed a clear domain correlation, indicating a strong coupling between the ferroelectric and antiferromagnetic order [4]. Temperature dependent measurements demonstrated that X-PEEM is able to distinguish between the different types of order. [1] S.-B. Choe et al., Science 304, 420 (2004).[2] F. Nolting et al., Nature 405, 76 (2000).[3] A. Scholl et al., Appl. Phys. Lett. 85, 4085 (2004).[4] T. Zhao et al., Nature Mat. 5, 823 (2006).The Advanced Light Source is supported by the Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
3:00 PM - **L8.2
Observing Atomic Scale Phenomena at Oxide Interfaces
Nigel Browning 1 2 , Miaofang Chi 1 , Lianfeng Fu 1 , Miriam Herrera 1 , Christoph Mitterbauer 1 , Quentin Ramasse 3
1 Chemical Engineering and Materials Science, University of California, Davis, California, United States, 2 Materials Science and Techbology Division, Lawrence Livermore National Laboratory, Livermore, California, United States, 3 National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractAs the complexity of oxide heterostructures increases, to permit more control to be exerted on the functionality of device structures, the properties of the interfaces between the components assume critical importance. This importance can either be the result of an unintended negative effect of the interface leading to a degradation in performance, or a beneficial effect leading to new and improved properties. In all cases, characterization of the atomic scale properties of interfaces, such as the structure (e.g. the formation of interface phases which can be as thin as a few atoms across), composition (e.g. segregation and diffusion of vacancies and impurities), and local bonding (electronic properties) is the key to a fundamental understanding of the interface. The ability to perform this characterization is afforded by the combination of atomic resolution Z-contrast imaging and electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM). The recent technical innovations of aberration correction (higher spatial resolution) and monochromation (higher energy resolution) have extended modern STEMs to the point where direct correlation of the experimental results with density functional theory is now possible. Through a combined experiment and theory approach to characterizing interfaces, the basic foundations of crystal chemistry (doping) and its effect on the properties of interfaces can be examined. In addition, information on the evolution of the interface structure and properties can be obtained through the use of in-situ stages in the STEM. By controlling the environment both before and during the experiment, key information on the processing conditions required to attain a particular structure (properties) can be determined. Here, the use of aberration corrected, monochromated and in-situ STEM methods will be described for a range of oxide interfaces, highlighting the current capabilities and discussing the future directions for interface characterization in the electron microscope.
3:30 PM - L8.3
Atomic Scale Characterization of Manganite Interfaces in the Aberration Corrected STEM.
Maria Varela 1 , Hans Christen 1 , Ho-Nyung Lee 1 , Jing Tao 1 , Andrew Lupini 1 , Stephen Pennycook 1 2 , Weidong Luo 2 , Sokrates Pantelides 2 , Javier Garcia Barriocanal 3 , Carlos Leon 3 , Jacobo Santamaria 3
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 Dept. of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee, United States, 3 Dept. Fisica Aplicada III, Universidad Complutense, Madrid Spain
Show AbstractComplex oxide films with perovskite structure are extremely interesting systems which exhibit an array of exciting physical behaviors including ferroelectricity, colossal magnetoresistance and high Tc superconductivity. But epitaxial complex oxide ultrathin films and heterostructures can be significantly affected by the presence of interfaces and may exhibit intriguing new physical properties quite different from the bulk. Understanding and harnessing these properties relies on a detailed atomic scale characterization of structure, chemistry and electronic properties. This is particularly true for heterostructures based on doped manganites, where the role of reduced dimensionality and chemical disorder in the phase separation scenario or on colossal magnetoresistance remains unclear. In this respect, the combination of aberration corrected scanning transmission electron microscopy and electron energy loss spectroscopy is a powerful tool that allows simultaneous atomic scale characterization of the chemistry, structure and also the electronic properties down to the single atom level. This work will present several examples of atomic resolution studies of the relationship between structure and electronic properties of manganite based thin films and interfaces, with complementary density-functional calculations. Examples will include charge transfer or localization in manganite/high Tc superconducting interfaces and manganite/insulating heterostructures.Acknowledgements: This research was sponsored by the Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, U.S. Department of Energy, under contract DE-AC05-00OR22725 with Oak Ridge National Laboratory, managed and operated by UT-Battelle, LLC.
3:45 PM - L8.4
Microstructure of Strained La2CuO4+delta Thin Films on Varied Substrates.
Jiaqing He 1 , Vladimir Y Butko 1 , Robert F Klie 1 , Ivan Bozovic 1 , Yimei Zhu 1
1 , brookhaven national lab, Upton, New York, United States
Show Abstract4:00 PM - L10:RRAMs
BREAK
L11: Interfacial Interactions
Session Chairs
Alexey Kalabukhov
Tsuyoshi Ohnishi
Friday PM, April 13, 2007
Room 3011 (Moscone West)
4:30 PM - L9.1
Cuprate-Manganite Interfaces-What Controls Their Properties?
Hanns-Ulrich Habermeier 1 , Christian Bernhard 2 , Jacques Chakhalian 1 , Bernhard Keimer 1
1 , Max-Planck-Institute-FKF, Stuttgart Germany, 2 , University Fribourg, Fribourg Switzerland
Show AbstractThe physical properties of complex oxides are characterized by the interplay of charge-,spin-,orbital and lattice degrees of freedom. Combining oxides with different spin-,charge- or orbital order opens generate an additional degree of freedom that can give rise to novel physical phenomena. We have studied the interface of the system La0.67.Ca.33MnO3 and YBa2Cu3O7 prepared by conventional PLD as an example representing the combination of ferromagnetic and superconducting oxides by a variety of techniques including neutron diffraction and XMCD analysis. It turns out that at the interface interaction effects are taking place at two different length scales. One is based on the self – injection of spin-polarized quasiparticles with a length scale of ~ 10nm, the other is a short range exchange interaction with a length scale of ~ 3 nm. The short range interaction gives rise to an antiferromagnetic coupling of the Mn and Cu spins across the interface. The results are discussed in the frame of orbital interactions across the interface. Furthermore, it could be shown that in FM/SC/FM trilayer systems a so far unknown coupling of adjacent magnetic layers occurs when the superlattices are cooled through the superconducting transition temperature. It is well established that two ferromagnetic layers are coupled through an intervening metallic layer by the Rudermann-Kittel-Kasuya-Yoshida (RKKY) mechanism. The sign of the coupling oscillates from positive to negative with the thickness of the metallic layer. On the other hand, the interaction between ferromagnetic (FM) and superconducting (SC) layers in a FM/SC/FM heterostructure is not well understood. Tentatively, we propose a coupling mechanism mediated by London screening currents to explain our observations.
4:45 PM - L9.2
Optical Magnetoelectric Effect Induced by Ferromagnetic Interfaces in Patterned Tricolor Oxide Superlattices.
Noriaki Kida 1 , Hiroyuki Yamada 2 , Hiroshi Sato 2 , Takahisa Arima 3 4 , Masashi Kawasaki 2 5 , Hiroshi Akoh 2 , Yoshinori Tokura 1 2 6
1 Multiferroics Project (MF), ERATO, Japan Science and Technology Agency (JST), Tsukuba, Ibaraki, Japan, 2 Correlated Electron Research Center (CERC), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan, 3 Spin Superstructure Project (SSS), ERATO, Japan Science and Technology Agency (JST), Tsukuba, Ibaraki, Japan, 4 Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, Japan, 5 Institute for Materials Research, Tohoku University, Sendai, Miyagi, Japan, 6 Department of Applied Physics, The University of Tokyo, Tokyo, Tokyo, Japan
Show Abstract5:00 PM - L9.3
Magnetic Interactions at Spinel-spinel and Spinel-perovskite Epitaxial Oxide Interfaces.
Rajesh Chopdekar 1 2 , Marco Liberati 3 , Yayoi Takamura 4 2 , Joanna Bettinger 2 , Brittany Nelson-Cheeseman 2 , Elke Arenholz 3 , Andrew Doran 3 , Andreas Scholl 3 , Lena Fitting 1 , David Muller 1 , Yuri Suzuki 2
1 Applied Physics, Cornell University, Berkeley, California, United States, 2 Materials Science and Engineering, University of California, Berkeley, Berkeley, California, United States, 3 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 4 Chemical Engineering and Materials Science, University of California, Davis, Davis, California, United States
Show Abstract5:15 PM - L9.4
Fabrication of Antiferromagnetic Cr2O3/Co Bilayer Thin Films for Exchange Bias Studies.
Sung Hwan Lim 1 2 , Makoto Murakami 1 , Shigehiro Fujino 1 , Jason Hattrick-Simpers 1 , Joshua Higgins 3 , Sam Lofland 4 , Manfred Wuttig 1 , Richard Greene 2 3 , Lourdes Salamanca-Riba 1 , Ichiro Takeuchi 1 2 3
1 Department of 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, University of Maryland, College Park, Maryland, United States, 4 Department of Physics and Astronomy, Rowan University, Glassboro, New Jersey, United States
Show Abstract