Symposium Organizers
Ramki Kalyanaraman Washington University
Ugo Valbusa University of Genova
Zhenyu Zhang Oak Ridge National Laboratory
N1: Ion Beam Induced Nanostructures in Thin Films
Session Chairs
Monday PM, November 27, 2006
Room 209 (Hynes)
9:30 AM - **N1.1
Self-forming Oriented Thin Film Nanostructures
James Harper 1 , R. Mark Bradley 2
1 Physics, University of New Hampshire, Durham, New Hampshire, United States, 2 Physics, Colorado State University, Fort Collins, Colorado, United States
Show AbstractIon-material interactions are discussed that can create nanoscale thin film structures with oriented crystallographic texture. Models of ion-induced sputter rippling and biaxial texture formation during ion assisted deposition share similar features, in that the directional effects of ion bombardment are balanced by the leveling effects of surface diffusivity. The resulting self-forming features, including well-defined surface ripples and biaxially textured microstructures, have been well documented. Here, we discuss combining these effects in multicomponent materials, and show the feasibility of obtaining self-forming oriented thin film nanostructures. Recent measurements of tilted fiber textures in metals (Ag, Al, Nb) and aluminum nitride (AlN) thin films are also presented, showing that the energetic arrival flux of sputtered atoms can induce in-plane orientation similar to the effects of ion bombardment. Additional mechanisms to control the morphology of nanoscale features are introduced by using mutually insoluble materials with large differences in surface diffusivity.
10:00 AM - **N1.2
Nanostructuring Surfaces by Ion Etching and Multilayer Epitaxy
Francesco Buatier de Mongeot 1
1 Dipartimento di Fisica, Università di Genova, Genova Italy
Show AbstractI will review recent results relative to the self-organised formation of laterally ordered arrays of periodic nanostructures induced by ion beam patterning and multilayer physical deposition. The influence of nanoscale morphological modifications on important properties in fields ranging from catalysis, to photonics to spintronics will also be explored. Concerning ion beam irradiation, anisotropic patterns oriented independently from the crystallographic texture can be formed exploiting the erosive and hyperthermal action of the ion beam. For example, using ion sculpting, it was possible to induce the formation of a regular Co nanowire array on an initially flat Co film supported on a Cu(001) substrate. The fourfold magnetic anisotropy of the flat film is correspondingly found to be forced to two-fold, with the easy magnetization axis lying parallel to the Co nanowires [1]. The generality of the approach is confirmed by similar observations for the Fe/Ag(001) system [2]. The action of the ion beam however cannot be simply described as the removal of few sputtered atoms, i.e. as the deposition of vacancies, because following ion impact much more adatoms are displaced, subsequently determining the surface morphology by diffusive relaxation which is especially relevant for crystalline metal substrates. This is demonstrated by experiments in which low energy ion irradiation of fcc(110) substrates induces the formation of Rhomboidal nanopyramid arrays bound by metastable facets composed by very open step configurations [3]. The peculiar step geometry corresponds to a high chemical reactivity with respect to CO dissociation [4]. Similarities are found in the case of physical deposition on crystalline metal substrates, where the formation of regular nanoscale patterns is generally found to be constrained by the symmetry of the substrate unit cell and pattern formation is now induced by kinetic instabilities which depend on the hierarchy of the surface diffusion barriers and on symmetry of the unit cell [5,6]. In connection to this last context, we have recently extended the possibility of growing regular arrays of metal nanoparticles, supported on technologically relevant polycrystalline dielectric substrates, pre-patterned by ion scultpting, observing interesting anisotropic optical properties. References [1] R. Moroni, et a. Phys. Rev. Lett. 91, 167207 (2003); D.Sekiba et al. Appl. Phys. Lett. 84, 762 (2004)[2] F.Bisio, et al. Phys. Rev. Lett. 96, 057204 (2006)[3] A.Molle et al. Phys. Rev. Lett. 93, 256103 (2004) [4] F.Buatier de Mongeot et al. Phys. Rev. Lett. in press[5] F.Buatier de Mongeot et al. Phys. Rev. Lett. 84, 2445 (2000)[6] F.Buatier de Mongeot, et al. Phys. Rev. Lett. 91, 016102 (2003); W.Zhu, Phys. Rev. Lett. 92 106102 (2004)
10:30 AM - N1.3
Enhanced Control of Porous Thin Film Morphology via Ion Bombardment.
Michael Fleischauer 1 , R. Joseph 1 , M. Brett 1
1 Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada
Show AbstractIon bombardment is commonly used to modify the structure and morphology of thin films fabricated using physical vapour deposition methods. Control over thin film morphology can also be realized by combining complex substrate motion with limited adatom mobility and self-shadowing in the highly oblique deposition regime. This process, known as GLancing Angle Deposition (GLAD) [1], has been used to fabricate films with a variety of morphologies including slanted posts, chevrons, square spirals, helices, vertical posts, and combinations thereof, on the tens to hundreds of nanometre scale. The search for new and improved GLAD morphologies has lead researchers to investigate complex substrate motion routines [2], post-deposition annealing [3], and even ion-assisted deposition [4]. It is therefore somewhat surprising that very few accounts of the effect of post-deposition ion bombardment have been described [5]. Colgan et al. noted ion bombardment normal to the (stationary) substrate has the effect of 'sharpening' vertical posts. Stationary substrates were also used in the account of ion-assisted GLAD [4]. Stationary substrates do not reflect the reality of modern GLAD. In this presentation we will describe the effect of ion bombardment during and after film deposition for a variety of morphologies fabricated using GLAD. Specific details will include the effect of post-deposition ion bombardment as a function of substrate motion (angle of incidence alpha, substrate position phi, velocity of alpha and phi) and milling conditions (current density, ion energy, mill time, etc.). We will also present methods to improve film morphology uniformity using multiple deposition / ion bombardment steps.[1] K. Robbie and M.J. Brett, J. Vac. Sci. & Tech. A, 15, 1460 (1997).[2] M.O. Jensen and M.J. Brett, Appl. Phys. A, 80, 763 (2005).[3] W.H. Wang and S. Chao, Opt. Lett., 23, 1417 (1998).[4] I. Hodgkinson and Q.H. Wu, Mod. Phys. Lett. B, 15, 1328 (2001).[5] M.J. Colgan, D. Vick and M.J. Brett,. Mat. Res. Soc. Symp. Proc. 636, D9.24 (2001).
11:00 AM - N1:IonFilms
BREAK
N2: Photon Induced Nanostructures in Thin Films
Session Chairs
Monday PM, November 27, 2006
Room 209 (Hynes)
11:30 AM - **N2.1
Dewetting and Pattern Formation in Nanoscopic Metal Films: A Theoretical Perspective.
Christopher Favazza 1 2 , Ramki Kalyanaraman 1 2 , R. Sureshkumar 3
1 Physics, Washington University in St Louis, St. Louis, Missouri, United States, 2 Center for Materials Innovation, Washington University in St. Louis, St. Louis, Missouri, United States, 3 Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri, United States
Show Abstract12:00 PM - N2.2
Instability-driven Nanoscale Pattern Formation in Co Films on SiO2 Under Pulsed Laser Interference Irradiation.
Christopher Favazza 1 2 , J. Trice 1 2 , R. Sureshkumar 3 , Ramki Kalyanaraman 1 2
1 Physics, Washington University in St Louis, St. Louis, Missouri, United States, 2 Center for Materials Innovation, Washington University in St. Louis, St. Louis, Missouri, United States, 3 Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri, United States
Show AbstractWe have recently shown that dewetting of nanoscopic metallic films under pulsed laser irradiation leads to robust pattern formation with spatial order [App. Phys. Lett. 88, 153118, 2006]. In this work we present the mechanisms of pattern evolution and formation under laser-interference irradiation of Co films on SiO2. Two-beam interference results in pattern evolution that consists of the film deforming during the early stages of irradiation with a spatially periodic length scale consistent with the interference spacing. For films above a critical thickness hc, continued irradiation leads to the formation of ordered nanowires, which eventually break-up into spatially ordered nanoparticles. The characteristic size and length scales of the nanoparticles were robustly determined by the film thickness and interference conditions. The selection of various hydrodynamic instabilities, including spinodal dewetting, Marangoni flow and Rayleigh-Plateau-like break-up of the nanowires, dictates the patterning process. We clearly identified regimes of experimental conditions in which each instability dominates. This identification was achieved through correlation of the observed nanomorphology with predictions based on instability time scales and their dependence upon film thickness. These results have considerable implications for large scale nanoprocessing of metal films as the final size and spacing of these nanoparticles are robust and highly predictable.
12:15 PM - **N2.3
Electronic Excitation-Assisted Self-Assembly of Nanostructures on Cu Surfaces by Pulsed Laser Light.
Hans-Joachim Ernst 1
1 DSM / Drecam / Spcsi, CEA Saclay, Gif Sur Yvette France
Show AbstractPhoton absorption on metals occurs through interaction with electrons. The excited electrons relax for the most part not radiatively, but by electron-electron and electron-phonon collisions, heating up the electron system and finally the crystal lattice. Therefore, interaction of high-power laser light often causes irreversible large-scale damage of the near-surface region, as the result of light-induced temperature rise that melts the material or temperature rise-induced thermomechanical strain. This damage is characterized by thresholds in absorbed photon fluence that translate into thresholds in transient temperature rise, which are material dependent but independent of laser wavelength. In our experiments, the peak transient temperature rise induced by pulsed laser light is limited to about 115 K, for the largest fluence of 114 mJ / cm2 (in 10 ns) applied. Therefore, laser illumination of Cu surfaces under these conditions should leave the structure unaltered. Instead, we do observe that Cu single crystal surfaces can be reversibly patterned by nanosecond pulsed laser light. The coupling of the laser to atomic-scale structural probes, Helium Atom Beam Scattering and Scanning Tunneling Microscopy, allowed us to discover /1/ that irradiation with green light of Cu surfaces held at a temperature of 300 K produces nanoscale pyramid-like structures, similar to those found in the growth of Cu on Cu (without laser irradiation). This atomic-scale restructuring is reversible and can be removed by annealing. Laser illumination at a static sample temperature of about 100 K, at which thermally activated mobility is inhibited, reveals the origin of the nanoscale pyramids. Their presence can be traced back to the appearance of a regular network of crossing dislocation lines, which extends in a coherent manner over the macroscopic area illuminated by the laser beam. Its orientation corresponds to the fcc easy glide system. The production of mobile adatoms out of these slip planes at elevated sample temperatures, in combination with the presence of the Ehrlich-Schwöbel barrier leads then to self-organization into nanoscale pyramid-like structural patterns. The activation of slip planes through laser action might indicate that the reversible atomic-scale restructuring of Cu has a similar origin as the previously observed irreversible plastic deformation caused by transient temperature-rise induced thermomechanical strain.However, in contrast to green light, infrared laser irradiation at equivalent absorbed optical energy density does not produce any structural change. This unforeseen difference in laser action of green and infrared light in a metallic system reveals that primary electronic excitation must play a key role in the atomic-scale restructuring of Cu surfaces. /1/ H.-J. Ernst, F. Charra, L. Douillard, Science 279, 679 (1998)
12:45 PM - N2.4
Growth of Tungsten Nanoripples Induced by Linearly Polarized Femtosecond laser.
Haitao Zhang 1 , Mingzhen Tang 2 , Jerry McCoy 2 , Tsing-Hua Her 1 2
1 Center for Optoelectronics and Optical Communications, The University of North Carolina at Charlotte, Charlotte, North Carolina, United States, 2 Department of Physics and Optics, The University of North Carolina at Charlotte, Charlotte, North Carolina, United States
Show AbstractLaser-induced chemical vapor deposition (LCVD) has been an important direct writing technique in microelectronics for decades, because of its ability to localize chemical reactions, hence the depositions on solid surfaces. Most techniques can only produce single line at one time, and laser beam needs to raster over substrate surfaces to get multiple lines. The requirement of tightly focused laser beam also impedes to further improve the feature size. Here, we present the growth of tungsten nanoripples induced by a single laser beam using LCVD process. The ripples are willow-leaf shaped, with a long strip and two pointed ends. The ripple width is less than 100 nm, and the ripple periodicity is about 130 nm, which is on the order of one third of the wavelength of the laser beam. The ripple orientation was found always parallel to the laser polarization, and hence can be controlled by changing the laser polarization direction. Different grating patterns were formed by scanning the laser beam along the substrate surface. Transverse pattern was formed when the scanning direction is perpendicular to the laser polarization, and longitudinal pattern was obtained when the scanning direction was parallel to the laser polarization. Effects of the laser power, exposure time, and scanning speed on the ripple formation were investigated. Different from the conventional laser-induced periodic surface structures (LIPSS) which can only occur by irradiating substrates near melting threshold, the tungsten nanoripples and gratings we report here can be heterogeneously deposited on a variety of substrates including insulators (glass, quartz, and sapphire etc.), wide band gap semiconductor (gallium nitride), and metals (gold, copper, and palladium etc.). Considering the simplicity of this process and material flexibility of CVD, our finding may provide a novel cost-effective patterning method to produce periodic subwavelength nanostructures of a wide range of materials.
N3: Surface Patterning by Photons
Session Chairs
Monday PM, November 27, 2006
Room 209 (Hynes)
2:30 PM - N3.1
Formation of Periodic Structures in Polymer-Metal-Nanocomposites by Irradiation with Femtosecond Laser Pulses.
Katrin Loeschner 1 , Andreas Kiesow 1 , Andreas Heilmann 1
1 , Fraunhofer Institute for Mechanics of Materials, Halle (Saale) Germany
Show AbstractThe spontaneous formation of periodic surface gratings or so called “LIPS” (laser induced periodic structures) due to laser irradiation has been investigated on surfaces of different materials, including semiconductors, metals, and dielectrics. It is generally accepted that the effect originates from interference of the incident laser light with the scattered light near the surface resulting in an intensity modulation on the irradiated material. To the best of our knowledge, up to now, this effect was not used to modify and to arrange metal nanoparticles to ordered structures within a polymer matrix. The nanocomposite thin film which was taken for the irradiation were produced by plasma polymerization or polymer sputtering and thermal evaporation of noble metals (gold, silver, copper). Due to the serial conduction of the deposition steps, the films possess a multilayer structure, i.e., the metal particle layer is embedded in the polymer matrix. The films were irradiated with linearly polarized fs-laser pulses in multishot as well as single shot regime. A mode-locked Ti-sapphire laser with regenerative amplification was used for irradiation. Pulse energies of about 1 to 150 µJ per pulse were applied. Within certain ranges of laser parameters, line-like periodic structure changes are created. The orientation of the lines is parallel to the laser polarization. The period length is determined by the irradiation wavelength. The laser-treated areas are characterized by longish regions with changes of particle size and shape distribution which alternate periodically with regions without apparent particle changes. The structure formation process contains two major steps: the periodical input of energy (interference) and the mechanism that converts the absorbed energy into a structural modification. We assume that after the ultrafast energy input, thermally driven diffusion processes, like reshapening and coalescence, are induced leading to the modification of the particle sizes and shapes.Beside a detailed description of the structural changes and the anisotropic optical and electronic film properties; we focus in our contribution on the discussion of the physical mechanism of the periodic structure formation. A series of irradiation experiments were performed to proof the applicableness of the classical LIPS-model to the effect reported here. A verification of different parameter dependences - laser polarization, wavelength, and angle of incidence as well as laser intensity - on the structure formation was made. Further we investigated the temporal development of the periodic structures by irradiating the material with different numbers of laser pulses.Technological applications, e.g. in the field of optics, are conceivable. This method to generate anisotropic metallic nanostructures inside a protecting polymer matrix, with period lengths simply selectable by the irradiation wavelength can be simply adapted forlarge-scale fabrication.
2:45 PM - N3.2
Dewetting Pattern Nanomorphology in Single-layer and Multi-layer Metal Films under Pulsed Laser Irradiation.
Hare Krishna 1 2 , Christopher Favazza 1 2 , R. Sureshkumar 3 , Ramki Kalyanaraman 1 2
1 Physics, Washington University in St. Louis, St. Louis, Missouri, United States, 2 Center for Materials Innovation, Washington University in St. Louis, St. Louis, Missouri, United States, 3 Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri, United States
Show Abstract3:00 PM - N3.3
Control of Growth and Morphology of a Crystal Surface by Induced Spatio-Temporal Oscillations of Surface Temperature.
Mikhail Khenner 1
1 Mathematics, State University of New York at Buffalo, Buffalo, New York, United States
Show AbstractI present a model for morphological evolution in the course of crystal growth from vapor phase, which is influenced by rapid spatio-temporal variations of temperature on a surface of a crystal. It is assumed that such temperature regime results from the interference heating by weak pulsed laser beams. When growth is thermodynamically stable, the surface relaxational dynamics is influenced by surface diffusion mass transport from hot to cold regions; this leads to accumulation of mass in cold regions and depletion in hot regions.In the thermodynamically unstable case the underlying spinodal instability coupled to diffusion mass fluxes from hot to cold regions leads to formation of equilibrium pyramids on a surface. The spacing between pyramids is controlled by a wave length of temperature field deviation from it's mean value. The value of a wave length is related to the angle between interfering beams and, therefore, tothe distance between adjacent interference fringes.The degree of control is strongly influenced by growth rate. Also, the new mechanism delays the onset of spatiotemporal chaos as the growth rate increases.The model is built upon the framework of classical continuum theory of morphological evolution of crystal surfaces. To attack the problem, I developed a mass-conserving finite volume numerical method that is capable of accurate computation of the large-slope solutions of unstable, strongly nonlinear, sixth order evolution PDE for surface height.
3:15 PM - N3.4
Nanoscale Self-Assembled Surface Structures of Silicon at Femtosecond Excitation.
Mohamed Elbandrawy 1 , Aleksey Bugayev 1
1 , Applied Research Center/Old Dominion University, Newport News, Virginia, United States
Show Abstract3:30 PM - N3:PhotSurf
BREAK
N4: Thin Film Nanostructures
Session Chairs
Francesco Buatier de Mongeot
Monday PM, November 27, 2006
Room 209 (Hynes)
4:30 PM - N4.1
Pulsed Laser Deposition of Nanolayer Structures Based on Bi and CdTe.
Arsham Yeremyan 1 , Karapet Avjyan 1 , Hovsep Avetisyan 1 , Ashot Khachatryan 1
1 Semiconductor Electronics Division, Institute of Radiophysics & Electronics of Armenia, Ashtarak Armenia
Show Abstract4:45 PM - N4.2
Pulsed Laser Deposition of Diamondlike Carbon-Metal Nanocomposite Films for Medical Applications
Roger Narayan 1 , Chunming Jin 1
1 Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina, United States
Show AbstractDiamondlike carbon thin films possess chemical inertness, wear resistance, and hardness properties close to those of diamond. Unfortunately, these films exhibit poor adhesion to metallic and polymeric materials used in medical prostheses. An innovative multicomponent target configuration was developed to incorporate metals into diamondlike carbon films during pulsed laser deposition. This approach to improve adhesion is based upon a theory that a more compliant entity within a diamondlike carbon film may accommodate large compressive stress, lower stored strain energy, and improve film adhesion. In addition, functionally gradient diamondlike carbon-metal composite films were prepared, which were characterized by a reduction in the concentration of metal atoms from the substrate/film interface to the film surface. The relatively high metal atom concentration at the film-substrate interface provides improved adhesion and wear resistance, and the relatively low metal atom concentration at the film surface provides maximal hardness and Young’s modulus at the load bearing interface. Diamondlike carbon-silver composite films demonstrated self-organization of silver into 2-5 nm self-assembled nanoparticle arrays. On the other hand, diamondlike carbon-titanium composite films demonstrate alternating ~ 2 nanometer-thick titanium carbide layers and diamondlike carbon layers. Hardness values for the diamondlike carobn-metal nanocomposite films and the functionally gradient diamondlike carbon-metal nanocomposite films were similar to those observed in layered tungsten carbide/diamondlike carbon and titanium carbide/ diamondlike carbon composite films prepared using electron cyclotron resonance chemical vapor deposition and magnetron sputtering techniques. The functionally gradient diamondlike carbon-metal composite films demonstrated exceptional wear resistance during linear tribometer testing. Specific metals may provide biological functionality to the diamondlike carbon-metal nanocomposite films. For example, diamondlike carbon-silver and diamondlike carbon-silver-platinum nanocomposite films were shown to possess antimicrobial efficacy against Staphylococcus aureus bacteria. Diamondlike carbon-metal composite films and functionally gradient diamondlike carbon-metal nanocomposite films have several potential applications, including use in machine tools and medical prostheses.
5:00 PM - N4.3
Structural and Magnetic Studies on Nanostructured Epitaxial NiPt Thin Films.
Nori Sudhakar 1 , G. Trichy 1 , J. Narayan 1 , H. Zhou 2
1 Department of Materials Science & Engineering, North Carolina State University, Raleigh, North Carolina, United States, 2 Los Alamos National Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show Abstract5:30 PM - N4.5
Self-organized Growth of Gold Nanoparticles in Amorphous Alumina Matrix.
Wei Wei 3 1 , Chunming Jin 1 , Honghui Zhou 2 , Andy Doraiswamy 1 , Roger Narayan 1 , Jagdish Narayan 3
3 Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States, 1 Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Chapel Hill, North Carolina, United States, 2 Superconducting Technology Center Materials Physics Application Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show Abstract
Symposium Organizers
Ramki Kalyanaraman Washington University
Ugo Valbusa University of Genova
Zhenyu Zhang Oak Ridge National Laboratory
N5: Photon-Assisted Surface Self-assembly
Session Chairs
Tuesday AM, November 28, 2006
Room 209 (Hynes)
9:30 AM - **N5.1
Desorption Mechanism of H From the Si(111) Surface Under Resonant Radiation.
Biao Wu 1
1 Institute of Physics, Chinese Academy of Sciences, Beijing China
Show AbstractA recent experiment [Science 312 (2006) 1024] shows that Hcan desorb in the form of H2 from the Si(111) surface after the Si-H vibrational mode is resonantly excited by an infrared laser. We present our latest theoretical results on the possible mechanism of this resonant desorption. We also discuss its potential applications.
10:00 AM - **N5.2
Resonant, Site-selective Desorption of Hydrogen from Si(111) using Infrared Photons.
Philip Cohen 1 , Zhiheng Liu 1 2 , Leonard Feldman 2 3 , Zhenyu Zhang 3 , Norman Tolk 2
1 Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota, United States, 2 Department of Physics and Astronomy, Vanderbilt Univeristy, Nashville, Tennessee, United States, 3 Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractExcitation and then scission of specific bonds has long been a goal of photon-induced chemistry but typicallythe energy deposited diffuses throughout the recipient structure, losing its specificity. We have usedinfrared photons at the Vanderbilt free electron laser (FEL) to excite the H-Si stretch vibration, causingresonant, non-thermal H2 desorption from Si(111)-H surfaces near room temperature. This is a very surprisingresult since the activation energy of thermal desorption is established as 2.4 eV [1] and the photon energy is0.26 eV. For the measurements a Si(111)-7x7 surface was prepared by flashing a sample to high temperatures underultrahigh vacuum conditions. The H coverage was achieved by exposing the clean Si surface to atomic Hprepared by dissociating H2 on a hot W filament. The FEL provides macropulses at 30 Hz comprised of 1 psmicropulses, each separated by 350 ps. Infrared was focused on the Si sample into an 0.8 mm in diameter spotat a fluence as much as 10 J/cm2 per macropulse. Desorption from each macropulse could be resolved. Thelinewidth of the radiation was set at 20 nm by a monochrometer. Using a mass spectrometer the desorption fromthe sample was measured, repeating the measurement at different locations. The incident wavelength was variedand we measured a peak in the desorption at 4.8 microns with a FWHM of 90 nm. Since this linewidth is lessthan what is required to excite higher order vibrational states because of the anharmonicity, a multiphotonladder climbing process, like that seen in scanning tunneling microscopy results, cannot produce thedesorption. Temperature programmed desorption (TPD) was compared to IR assisted desorption of a layer ofcoadsorbed H and D. The TPD of H on Si indicated that a monohydride was formed. In the coadsorptionexperiment, TPD showed mainly D2 while IR assisted desorption showed mainly H2. This result shows that themeasured desorption could not be caused by local heating. Finally, the desorption yield was quadratic in theincident fluence.A variety of atomic level mechanisms which may explain the phenomenon will be discussed. For example wespeculate that desorption results from a second order excitation in which two neighboring H atoms pair. Thisroom temperature process may have important applications in epitaxial growth, hydrogen generation, and othertechnologies that benefit from room temperature chemistry.
10:30 AM - N5.3
Photo-Induced Structural Changes in Titanium Alkoxides for Directing Molecular Assembly.
J. David Musgraves 1 , Jeanette Blaine 1 , Barrett Potter 1 , Robin Sewell 2 , Timothy Boyle 2
1 Materials Science and Engineering, University of Arizona, Tucson, Arizona, United States, 2 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractA new, optically directed molecular assembly methodology is under investigation that integrates photoinduced structural modification with the rational design of complex metal alkoxide precursors to control the solution-based synthesis of metal oxides. The strategy is intended to enable the selective photo-activation of reaction points about the metal center, influencing the development of intermolecular topology and the ensuing higher order structure. Research has focused on the photophysical responses of mono- and polynuclear heteroleptic Ti precursors: (OPy)2Ti(4MP)2, (OPy)2Ti(4AP)2 and [Ti2(μ-THME)(OMP)2(OPri)3]2 with OPy=C6H6NO, 4MP=OC6H4SH, 4AP=OC6H4NH2, THME=C5H12O3, OMP=CH3C6H4OH, and OPri=C3H7O under UV-irradiation. Excitation wavelength and fluence-dependent photostructural modifications in these compounds are investigated in solution and in the solid state using vibrational and UV-Vis spectroscopies. Selective photomodification of vibrational modes associated with specific ligands is observed. Interpretation of these results is supported by DFT-based computational modeling of the precursor molecular structure. The ramifications of these results in terms of their impact on the evolution of nanostructure in a sol-gel processing context will be discussed.
10:45 AM - N5.4
UV-aided Macroscopic Scale Fabrication of Ordered Ag Nanoparticles Array Using Diblock Copolymer Film as Nanotemplate
Jingze Li 1 , Kaori Kamata 1 2 , Tomokazu Iyoda 1 2
1 Division of Integrated Molecular Engineering, Chemical Resources Laboratory, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan, 2 CREST, Japanese Science and Technology Agency, Kawaguchi, Saitama, Japan
Show AbstractTo efficiently fabricate regular pattern of metallic nanostructure onto various substrates is of growing interest because of its potential application in electronics, photonics, plasmonics, and panel display. During the past two decades, a great number of attempts have been done, in which template assisted nanofabrication technique is one of the promising ways due to its capability in mass production. With respect to conventional templates, diblock copolymer provides a rich diversity of structures at nanometer length scale. In this report, a novel hybrid means, diblock copolymer templated photochemical fabrication, has been demonstrated to one-step generate and attach ordered array of Ag nanoparticles onto solid substrates. A series of amphiphilic diblock copolymers, specially designed and synthesized in our group,1 forms periodically hexagonal nanostructure by self-organization,2 where hydrophilic nanocylinders are uniformly dispersed in hydrophobic matrix.3 Then, metal salt is selectively hosted by hydrophilic blocks of copolymer template. After UV treatment is finished, hexagonally arranged nanoparticles appear on both conducting and insulating solid substrates confirmed by AFM and SEM. It should be mentioned that the ordered array of nanoparticles can spread over several ten μm2, which is the maximum scan range of the used AFM. Finally, UV-vis absorption spectrum shows the characteristic plasmon resonant peak of Ag nanoparticles. Additional characterization such as XPS and EDAX has further identified that major component of nanoparticles is metallic Ag. By adjusting the molecular weight of the two blocks, either the period of the diblock copolymer template or the diameter of hydrophilic nanodomain can be intentionally tuned. Correspondingly, the templated Ag arrays with various interparticle distances are obtained. This simple and effective method can be further applied to generate periodic array of organic, inorganic, and other metal nano-objects.(1) Tian, Y. Q.; Watanabe, K.; Kong, X. X.; Abe, J.; Iyoda, T., Macromolecules 2002, 35, 3739-3747.(2) Yu, H. F.; Okano, K.; Shishido, A.; Ikeda, T.; Kamata, K.; Komura, M.; Iyoda, T., Adv. Mater. 2005, 17, 2184-2188.(3) Morikawa, Y.; Nagano, S.; Watanabe, K.; Kamata, K.; Iyoda, T.; Seki, T., Adv. Mater. 2006, 18, 883-886.
11:00 AM - N5:PhotSurf
BREAK
N6: Ion Beam Induced Surface Pattern Formation
Session Chairs
Tuesday PM, November 28, 2006
Room 209 (Hynes)
11:30 AM - **N6.1
Kinetic Mechanisms Controlling Ion-Induced Pattern Formation.
Eric Chason 1 , Wai Lun Chan 1
1 Engineering, Brown University, Providence, Rhode Island, United States
Show AbstractSputtering by low energy ion beams can induce a wide variety of patterns (a.k.a sputter ripples) to form on many different surfaces. The patterns are self-organizing, i.e., they form spontaneously with no template or modulation of the ion beam. Studying their formation, therefore, sheds light on how different fundamental kinetic processes (ion sputtering, defect generation and surface diffusion) interact to control the overall surface evolution. In this presentation, we will discuss different kinetic regimes of pattern formation in terms of the mechanisms controlling their growth. An instability theory initially proposed by Bradley and Harper will be used as a framework for explaining the transitions between different regimes. Results of kinetic Monte Carlo simulations and experiments will be used to explore the predictions of the model and relate the behavior to fundamental surface kinetic processes. This work was supported by the U.S. Department of Energy under contract DE-FG02-01ER45913.
12:00 PM - N6.2
Linear Stability of Ion Sputtered Ssurfaces: Sigmund-Bradley-Harper Theory Revisited.
Benny Davidovitch 1 , Michael Brenner 1 , Michael Aziz 1
1 DEAS, Harvard University, Cambridge, Massachusetts, United States
Show Abstract12:15 PM - N6.3
Nano Patterning by Dual Ion Beam Sputtering.
Min-Woong Joe 1 , Byungnam Kahng 1 , Jae-Sung Kim 2
1 Physics, Seoul National University, Seoul Korea (the Republic of), 2 Physics, Sook Myung Women's University, Seoul Korea (the Republic of)
Show AbstractIon beam sputtering has shown possibilities to form ordered nano-structures such as nano dots and ripples. Most of the previous works are, however, carried out by a single ion gun, and the fabricated nano structures are then limited. In the present work, we report a novel approach for the nano-fabrication that employs two ion guns; We oriented the two ion guns by 90 degree rotated to each other, and 73 degree from surface normal. In this condition, each ion gun produces well ordered nano-ripples on both Au(001) and Pd(001). When the two guns are simultaneously operated, there form crosshatched square patterns of holes bounded by nano scale ridges for Au(001), while it does not produce such interference pattern for Pd(001). The interfered nano-pattern on Au(001) shows various defects that impede the formation of extended ordered structures. We will discuss the conditions for the interference of ripples and their mechanisms, and the possibilities to optimize the order of the interfered nanopatterns.
12:30 PM - N6.4
Effect of Nanoscale Mass Rearrangement on Surface Morphology Evolution Due to Ion Bombardment.
Harley Johnson 1 , Nagarajan Kalyanasundaram 1 , Jonathan Freund 1 2
1 Mechanical and Industrial Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 Aerospace Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractWe study the effect of nanoscale mass rearrangement caused by individual ion impacts leading to the sputter erosion surface instability. We perform molecular dynamics simulations of 500eV argon ion bombardment of silicon at the nanoscale to obtain a response function that represents the continuum change in height at any surface coordinate due to an average impact at a random point on the surface. The impact response function is a function of incidence angle and includes the effects of both sputtering and mass rearrangement. Mass rearrangement is shown to be more significant than sputtering in changing the surface height due to single ion impacts. Statistically averaged impact response functions are then combined with continuum surface diffusion equations to perform a multiscale simulation on micrometer sized systems. The multiscale simulations predict ripple and/or dot formation, with the amplitude of patterns saturating at long times. The saturating amplitude calculated in the simulations matches well with similar experimental observations. The mass rearrangement mechanism explains these observations and suggests significant deviations from the Bradley-Harper and Makeev-Barabasi theories of pattern formations. These differences are explained and quantified for pattern formation at both normal and off-normal beam incidence angles.
12:45 PM - N6.5
Ion-irradiation Induced Surface Ripples on Sapphire
Hua Zhou 1 , Lan Zhou 1 , Yiping Wang 1 , Randall Headrick 1 , Ahmet Ozcan 2 , YiYi Wang 2 , Gozde Ozaydin 2 , Karl Ludwig Jr. 2
1 Physics, University of Vermont, Burlington, Vermont, United States, 2 Physics, Boston University, Boston, Massachusetts, United States
Show AbstractEnergetic particle bombardment on surfaces is known to produce 2-D (ripples or wires) and 1-D (dot) structures at the submicron or nano-scale by a self-organization process. Recently, significant experimental and theoretical effort has been expended in order to develop ion bombardment patterning methods for the production of well-ordered periodic nanostructures on various substrates, from semiconductors to metals. These studies have demonstrated the potential to tailor surface morphology, so as to related physical properties, for novel optoelectronic and spintronic applications, and provided new insights into the mechanisms of the instability-driven self-organization process. In this talk, a study of ripple formation on sapphire surfaces by ion beam irradiation and its application as templates for the production of laterally modulated magnetic nanostructures will be presented. Surface characterization by in-situ synchrotron grazing incidence small angle x-ray scattering and ex-situ atomic force microscopy for the wavelength, shape and amplitude of sapphire ripples is performed. The wavelength can be varied over two orders of magnitude by changing the ion incidence angle. The kinetics of ripple formation is discussed within the linear Bradley-Harper theory for different surface smoothing mechanisms. However, strong smoothing is inferred from the observed ripple wavelength near normal incidence, which is not consistent with either surface diffusion or viscous flow relaxation. Furthermore, off-specular x-ray diffuse scattering is employed to investigate the morphology (surface/interface) conformity of magnetic thin films grown on nanorippled sapphire surface. SQUID study of the effects of lateral nanostructuring on magnetic properties, such as anisotropy and switching behaviors, will also be presented.
N7: Ion-Induced Patterning of Semiconductor Surfaces
Session Chairs
Tuesday PM, November 28, 2006
Room 209 (Hynes)
2:30 PM - **N7.1
Ion-assisted Pattern Formation at Semiconductor Surfaces and Their Application to Fabricate Nanomagnet Arrays.
Christian Teichert 1
1 Institute of Physics, University of Leoben, Leoben Austria
Show AbstractBesides the well established spontaneous pattern formation in strain-induced heteroepitaxial growth [1], also ion irradiation of semiconductor surfaces [2] opens an elegant and efficient route towards fabrication of large-scale arrays of uniform semiconductor nanostructures. After a brief review on both types of pattern formation, it will be shown for the model system SiGe/on Si(001) how the combination of both procedures can result in additional self-organized patterns, e.g., in checkerboard patterns of {105} faceted pyramids and pits [3]. Further, the pattern transformation of the SiGe films will be studied under subsequent Ar ion erosion [4].Since the resulting nanostructure arrays cover the entire wafer surface, they can be used as large-area nanopatterned templates for subsequent deposition of magnetic thin films [5]. This will be illustrated for the shadow deposition of cobalt onto self-organized, mesa structured SiGe templates on the one hand [6] and on ion bombardment induced GaSb dot patterns on the other hand. X-ray magnetic circular dichroism (XMCD) measurements using a photoemission electron microscope as well as magnetic force microscopy reveal that the resulting nanomagnets with lateral dimensions down to 30 nm are single domain.[1] C. Teichert, Phys. Rep. 365 (2002) 335.[2] S. Facsko, et. al., Science 285 (1999) 1551; T. Bobek, et al., Phys. Rev. B 68 (2003) 085324.[3] C. Teichert, et al., Thin Solid Films 380 (2000) 25.[4] C. Hofer, et al., Nucl. Instrum. Meth. B 216 (2004) 178.[5] C. Teichert, Appl. Phys. A 76 (2003) 653.[6] A. M. Mulders, et al., Phys. Rev. B 71 (2005) 214422.This research is supported in the framework of the European Project NAMASOS (Nanomagnets by Self-Organisation, Grant No. STRP 505854-1) and has been performed in collaboration with C. Hofer (Leoben), K. Lyutovich and E. Kasper (Stuttgart), T. Bobek, and H. Kurz (Aachen), L. Gridneva and D. Arvanitis (Uppsala), A. Locatelli and S. Heun (Trieste), M.A. Niño, J.J. de Miguel, and R. Miranda (Madrid).
3:00 PM - N7.2
The Role of Secondary Ion Beam Parameters on the Formation and Ordering of Ripple and Dot Structures on Si and Ge Surfaces.
Bashkim Ziberi 1 , Frank Frost 1 , Lutz Theresa 1 , Michael Tartz 1 , Horst Neumann 1 , Bernd Rauschenbach 1
1 , Leibniz-Institut für Oberflächenmodifizierung e. V., Leipzig Germany
Show AbstractIn the recent years ion beam sputtering becomes a promising technique for large area nanostructuring of surfaces. Due to self-organization processes caused by low-energy ion beam erosion, well ordered ripple and dot patterns can evolve on different semiconductor materials [1-6]. This pattern formation is related to the complex interplay between curvature dependent sputtering and different surface relaxation mechanisms. However the main disadvantage of these self-organized processes is the lack of long-range ordering.In this contribution results for the evolution of ripple and dot nanostructures on Si and Ge surfaces with sizes below 100 nm, using Xe+ ions (ion energy ≤ 2000 eV) for oblique ion incidence without sample rotation at room temperature, are presented. It is well known that the evolution of ripple and dot patterns depends on sputtering conditions like ion energy, ion incidence angle and ion fluence. For example by varying the ion incidence angle a dot-ripple-dot transition is observed [7]. Additionally, the settings of the multiaperture two-grid ion optical system of the Kaufman-type broad beam ion source used in the experiments also influence the evolution of patterns. These settings, neglected up to now in many studies, influence the angular distribution of ions within the ion beam and the beam divergence. One of the ion optical parameters is the voltage Uacc applied on the second grid called acceleration grid. This parameter is crucial not only for the evolution of patterns on the surface but also for their lateral ordering. For the given experimental setup of the ion source an increase of Uacc leads to an increase of angular distribution and beam divergence and the opposite for decreasing values. Additionally by varying the beam divergence a topographical transition, for example, from ripples to dots is observed on Si and Ge surfaces. Further, by choosing appropriate values of Uacc and the ion incidence angle an almost perfect array of dot patterns covering the whole sample area is observed.[1]S. Facsko, T. Dekorsy, C. Koerdt, C. Trappe, H. Kurz, A. Vogt, and H. L. Hartnagel, Science 285, 1551 (1999).[2]F. Frost, A. Schindler, and F. Bigl, Phys. Rev. Lett. 85, 4116 (2000).[3]F. Frost, B. Ziberi, T. Höche, and B. Rauschenbach, Nucl. Instrum. Meth. B 216, 9 (2004).[4]B. Ziberi, F. Frost, T. Höche, and B. Rauschenbach, Appl. Phys. Lett. 87 (2005).[5]B. Ziberi, F. Frost, Th. Höche, and B. Rauschenbach, Phys. Rev. B 72, 235310 (2005).[6]R. Gago, L. Vazquez, R. Cuerno, M. Varela, C. Ballesteros, and J. M. Albella, Appl. Phys. Lett. 78, 3316 (2001).[7]B. Ziberi, F. Frost, and B. Rauschenbach, Appl. Phys. Lett. 88 (2006).
3:15 PM - N7.3
Studies of Si Surface Morphology Evolution During High Temperature Ar+ Ion Bombardment.
Gozde Ozaydin 1 2 , Ahmet Ozcan 2 , Chris Sanborn 2 , Karl Ludwig 2 , Hua Zhou 3 , Lan Zhou 3 , Randall Headrick 3
1 Aerospace and Mechanical Engineering, Boston University, Boston , Massachusetts, United States, 2 Physics, Boston University, Boston , Massachusetts, United States, 3 Physics, University of Vermont, Burlington, Vermont, United States
Show AbstractA systematic study of Si surface evolution during high temperature Ar+ ion is reported. Real-time grazing incidence small-angle x-ray scattering (GISAXS) measurements are performed at the National Synchrotron Light Source of Brookhaven National Laboratory. Ex-situ atomic force microscopy is also used to provide real-space information.Si (100) samples are bombarded by Ar+ ions from a PHI sputter gun at normal incidence at ion energies of 500 and 1000 eV and at temperatures ranging from room temperature to 750°C. For temperatures lower than 400°C little roughening is observed on the surface. Above this temperature, formation of correlated roughening is observed during normal incidence bombardment at both 500 eV and 1000 eV. A separate study on the smoothening of ripples by ion bombardment is also performed. The ripples are formed on the Si(100) surfaces by off-axis Ar+ ion bombardment. Then the real time smoothening of these ripples is monitored using GISAXS during normal incidence ion bombardment of the surface at room temperature or at higher temperatures. It is observed that, while the ion bombardment at room temperature is sufficient to smoothen the ripples, ion bombardment at elevated temperatures up to 400°C accelerates the smoothening process. This work is partially supported by NSF DMR-0507351.
3:30 PM - N7.4
Nanoporosity, Stress Formation and Surface Roughening During Ion Bombardment of Ge Thin Films: the Role of Point Defects and Plastic Flow.
Stefan Mayr 1
1 I. Physikalisches Institut, Universitaet Goettingen , Goettingen Germany
Show Abstract3:45 PM - N7.5
Anisotropic Nanopillars Obtained by Ion-sputtering: Symmetry of the Wetting Properties.
Elin Sondergard 1 , Anne Lelarge 1 , Pascal Naël 1 , Fabrice Oehler 1 , Damien Vandembroucq 1 , Nathalie Brun 2
1 Laboratoire Surface du Verre et Interfaces, UMR 125 CNRS/Saint-Gobain, Aubervilliers France, 2 Laboratoire de Physique des solides, CNRS UMR 8502, Universiti Paris Sud, Orsay France
Show Abstract4:00 PM - N7:IonSemi
BREAK
N8: Ion and photon Induced Nanostructures: Characterization and Applications
Session Chairs
Tuesday PM, November 28, 2006
Room 209 (Hynes)
4:30 PM - N8.1
Vertically Aligned Carbon Nanotubes Growth Using Self-assembled Ni Nanoparticles Produced by Ion Implantation.
Daniel Baptista 1 2 , Joao Marcelo Lopes 1 , Marcio Morschbacher 1 , Sharvari Dalal 2 , Shu-Pei Oei 2 , Ken Teo 2 , Willian Milne 2 , Fernando Zawislak 1
1 Instituto de Física, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil, 2 Engineering Department, University of Cambridge, Cambridge United Kingdom
Show AbstractThe catalytic growth of vertically aligned carbon nanotubes (CNTs) by plasma enhanced chemical vapor deposition (PECVD) and semiconductor nanowires by physical vapor deposition (PVD) opens up the possibility of exploiting these 1-D nanostructures in reliable bottom-up devices. Carbon nanotubes arrays grown by PECVD have been shown to be promising for applications in sensing and field emission, while vertically aligned carbon nanotubes arrays would be especially useful in micro/nanoelectromechanical systems (M/NEMS).Using e-beam lithography, one can define catalyst positions on substrates and therefore generate localized and selective CNT growth. However, limitations are encountered when patterning large areas or placing catalyst particles for high aspect ration nanostructures. As an alternative method, the use of catalyst metal particles produced by ion implantation and post-annealing treatment has attracted interest [1]. The main idea is to produce embedded catalyst metal nanoparticles into etchable layers such as SiO2. By performing selective etching, it is possible to directly expose the catalyst where desired. We report the formation of self-assembled Ni nanoparticles by ion implantation and their application as catalytic seeds for the growth of vertically aligned carbon nanotube arrays. By implanting Ni ions at 100-130keV at doses of 5x10^15 and 1x10^16 Ni.cm^-2 respectively, Ni nanoparticles were formed inside a 450 nm SiO2 film on Si substrates. Post-annealing treatments at 700, 900 and 1100°C in a N2 atmosphere were performed, resulting in the formation of self-assembled Ni nanoparticles with mean diameter of approximately 3, 5 and 15 nm respectively. Diluted HF solution was used to etch the SiO2 layer until the nanoparticles were exposed to the surface. Finally, vertically aligned carbon nanotubes arrays were grown by PECVD using C2H2 and NH3 gases using controlled conditions [2]. The samples were characterized using scanning electron microscopy (SEM), high-resolution transmission electron (HRTEM) and atomic force microscopy (AFM). The spatial distribution as well as the diameter and crystallinity of the Ni nanoparticles are analyzed for each annealing temperature. The well-aligned CNTs arrays are analyzed in terms of their density as well as the diameter of the tubes. The correlation between the grown tubes and the dimensions of the nanoparticles is discussed.[1] A.R. Adhikari, M.B. Huang, D. Wu, K. Dovidenko, B.Q. Wei, R. Vajtai, and P.M. Ajayan, Applied Physics Letters, 86, 053104, 2005.[2] K.B.K. Teo, S-B Lee, M. Chhowalla1, V. Semet, Vu Thien Binh, O. Groening, M. Castignolles, A. Loiseau, G. Pirio, P. Legagneux, D. Pribat, D. G. Hasko, H. Ahmed, G. A. J. Amaratunga and W.I. Milne, Nanotechnology 14, 204–211, 2003.
4:45 PM - N8.2
Highly Charged Ion Modified Magnetic Tunnel Junctions
Holger Grube 1 , Joshua Pomeroy 1 , Andrew Perrella 1 , John Gillaspy 1
1 Atomic Physics Division, NIST, Gaithersburg, Maryland, United States
Show AbstractHighly charged ions (HCIs) carry high potential energies, which are deposited very locally on impact surfaces to modify or ablate areas of only a few square nanometers per HCI impact. This allows the fabrication and study of a wide range of nanostructures and materials. Our HCI source allows us to select element, charge state, kinetic energy, and dose. We have used highly charged ions such as Xe44+ to modify ultrathin oxide barriers in magnetic tunnel junctions in order to tune their electrical properties. We report on the systematic dependence of the resistance area (RA) product and of the magnetoresistance of HCI modified multilayer magnetic tunnel junctions (MTJ) on HCI dose, charge state, kinetic energy and oxide thickness. We have analyzed the properties of individual HCI created conduction channels through ensemble measurements. One of our goals is to use highly charged ions to controllably lower the RA value of MTJs while preserving useful magnetoresistance for applications requiring low RA such as hard drive read heads.
5:00 PM - N8.3
Defects Study in Gold Surfaces produced by Ion Bombardment.
Esther Carrasco 1 , Oscar Rodríguez de la Fuente 1 , Miguel Garcia 1 2 , Cesar de Julian 3 , Juan Rojo 1
1 Física de Materiales, Universidad Complutense, Madrid Spain, 2 , Instituto de Magnetismo Aplicado UCM-CSIC-Renfe, Las Rozas, Madrid, Spain, 3 Dipartimento di Fisica, Università di Padova, Padova Italy
Show Abstract5:15 PM - N8.4
Selective Formation of Sub-10 nm Dot Array Aided by Electron Beam.
Jung-Sub Wi 1 , Tae-Yon Lee 2 , Hyo-Sung Lee 1 , Sung-Wook Nam 1 , Hyun-Mi Kim 1 , Kyung Ho Shin 3 , Ki-Bum Kim 1
1 School of Materials Science and Engineering, Seoul national university, Seoul, Seoul, Korea (the Republic of), 2 Nano Systems Institute - National Core Research Center, Seoul National University, Seoul, Seoul, Korea (the Republic of), 3 Future Technology Research Division, Korea Institute of Science and Technology, Seoul, Seoul, Korea (the Republic of)
Show AbstractN9: Poster Session: Self-Assembly and Pattern Formation by Ion and Photon Beams
Session Chairs
Wednesday AM, November 29, 2006
Exhibition Hall D (Hynes)
9:00 PM - N9.1
Self-organization Processes in the Nanostructures Formation of Crystal Lattices by Low-energy Ion Irradiation.
Volha Abidzina 1 , I. Tereshko 1 , A. Tereshko 1 , V. Glushchenko 1 , I. Elkin 2 , D. Ila 3
1 , Belarusian-Russian University, Mogilev Belarus, 2 , 'KAMA VT' Research and Production Enterprise, Mogilev Belarus, 3 , Center for Irradiation of Materials, Alabama A&M University, Normal, Alabama, United States
Show AbstractThe aim of this work is to show the results of the experimental studies of the formation of nanoclusters in metals by the low-energy ion irradiation and computer simulation of nonlinear effects on an atomic scale.The subjects of the investigation were polycrystalline armco-iron and instrumental steels. All samples were irradiated by low-energy ions of residual gases in discharge plasma. The fine dislocation structure of the samples was being studied using the transmission electron microscopic method. We showed that the process of low-energy influence led to the formation of a complex multilayer structure in the near-surface area. There were the layers with the amorphous structure, a microcrystalline and nanocrystalline structure. The low-energy ion irradiation led to a change of physical and mechanical properties of the irradiated materials. It is necessary to emphasize that samples behavior depends on the time elapsed after stopping the irradiation.These modifications in materials could be understood within the conception of active self-organizing processes in crystal lattices. We showed by a computer simulation that nonlinear oscillations were excited in the system of coupled atomic oscillators in crystal lattices, which resulted in the formation of nanoclusters.
9:00 PM - N9.2
Ion Induced Self-organization on Pre-patterned Si Surfaces.
Theresa Lutz 1 , Bashkim Ziberi 1 , Renate Fechner 1 , Dietmar Hirsch 1 , Klaus Zimmer 1 , Frank Frost 1 , Bernd Rauschenbach 1
1 , Leibniz-Institut für Oberflächenmodifizierung e. V., Leipzig Germany
Show Abstract9:00 PM - N9.3
Simultaneous Surface Nanostructuring and Optical Activation of Lithium Fluoride crystals by Ion Beam Irradiation
Valentina Mussi 1 , Francesco Buatier de Mongeot 1 , Andrea Toma 1 , Corrado Boragno 1 , Ugo Valbusa 1 , T. Marolo 2 , Rosa Maria Montereali 2
1 Dipartimento di Fisica, Università di Genova, Genova Italy, 2 Advanced Physical Technologies, ENEA, C.R. Frascati, Frascati Italy
Show Abstract First results on simultaneous surface nanostructuring and optical activation of lithium fluoride crystals by ion beam irradiation will be presented [1]. An 800 eV off-normal Ar+ ions beam at different ion doses was used to produce periodic nanostructures at the surface of the crystal while generating optically active electronic defects. The samples were studied by atomic force microscopy and optical spectroscopy. After ion sputtering, smoothening of the initial quite large random roughness is achieved and well defined self-organized ripple structures appear, with a mean periodicity of 30 nm and a mean height of 3 nm. The simultaneous optical activation of the samples is due to the stable formation of F2 and F3+ centers with intense photoluminescence in the visible spectral range.[1]V. Mussi, et al. APPLIED PHYSICS LETTERS 88, 103116 (2006)
9:00 PM - N9.4
Large Area Ripple Formation by Ion-beam Irradiation of Silicon and Silica Surfaces.
Emanuela Piscopiello 1 , Marcello Massaro 1 , Luciana Mirenghi 1 , Tarcisio Nocco 1 , Laura Capodieci 1 , Leander Tapfer 1
1 UTS MAT, ENEA, Brindisi Italy
Show AbstractThe periodic ripple formation on silicon and fused silica surfaces by ion beam irradiation was investigated as a function of ion energy, flux (dose), angle of incidence and substrate temperature. The silicon and silica surfaces were bombarded by Ar+ (and Xe+) ions of energy between 30 and 120keV and different angles of incidence were considered: 30°, 45°, 60° and 75°. The ion dose was kept at 1.0x1018 at/cm2 and the beam current was in the range 30-50 μA/cm2. Ion beam irradiation experiments were carried out at room temperature and TS = 400°C. All the experiments were made on a 200keV high current Danfysik 1090 ion implanter in a high vacuum chamber and in scanning (beam sweeping) as well as stationary beam mode.The surface ripple structures were investigated by atomic force microscopy, X-ray reflection and diffuse scattering, and transmission electron microscopy. The chemical modification of the surfaces (stoichiometry, contaminations, etc.) was analyzed by X-ray photoelectron spectroscopy. The crystalline structure of the ion irradiated (100) Si surface was also investigated by high-angle high-resolution X-ray diffraction and reciprocal space mapping and cross section high-resolution transmission electron microscopy. Besides the surface morphology also the crystalline – amorphous transition of the ion bombarded (100) Si surface was investigated. Generally, the most pronounced ripple structure was obtained by using a lower ion beam energy of about 40keV (Ar+) and incidence angle 60° at RT. In the case of scanning mode ion irradiation the surface morphology is uniform and homogeneous over a large surface area of about 10cm2. At higher ion beam energies the ripple structure is still well observed, however, the amorphization phenomenon is enhanced and the crystalline part of the surface modulation is strongly reduced. Under substrate heating conditions a much “rougher” surface is obtained, where the surface corrugation is even more evidenced. This finding is explained in terms of different surface energy conditions and considering a “softening” of the chemical bonds near the surfaces.
9:00 PM - N9.5
Dynamical Evolution of Silicon Nanowires in Intense Laser Fields Studied Quantum Mechanical.
Anna Mazzone 1
1 IMM, CNR , Bologna Italy
Show Abstract9:00 PM - N9.6
Electron-beam Assisted Nano-manufacturing of Novel Nanocarbons: Topological and Curvature Perspectives.
Sanju Gupta 1 , Avadh Saxena 2
1 Physics and Materials Science, Missouri State University, Springfield, Missouri, United States, 2 Theoretical , Los Alamos National Lab, Los Alamos, New Mexico, United States
Show AbstractSevere environmental tolerability is the prime factor in the development of novel space materials exhibiting excellent physical properties accompanied by lightweight, reusability, and multifunctional capabilities. Carbon nanotubes (both the single- and multi-walled), in the family of nanostructured carbons, are of great interest because of several unsurpassable physical properties and it needs to be shown that they are physically stable and structurally unaltered when subjected to radiation. In addition to testing them for space applications, when exposed to high energy electron beam from transmission electron microscopy, the results seem quite promising in terms of nano-engineering/ nano-manufacturing for producing novel nanocarbons [1-3]. Experimental studies of effects of electron beam irradiation on carbon nanotubes show that multi-walled ones tend to be relatively more robust than their single-walled kins. The increased exposure on an individual bundle of single-wall nanotubes promoted graphitization, pinching, and cross-linking analogous to polymers forming an intra-molecular junction (IMJ) within the area of electron beam focus, possibly through aggregates of amorphous carbon [2,3]. Formation of novel nanostructures (nano-ring and helix-like) due to irradiation are observed. These studies shed light on the dynamics of nanomanufacturing and a regime of possible relevance of these materials for: (i) short-term space missions; (ii) radiation hard programmable logic circuits; and (iii) radiation pressure sensors. It is suggestive that a local reorganization occurs. Through resonance Raman spectroscopy and related techniques we also elucidate an important notion of global topology and curvature at nanoscale which points to an emergent paradigm of Curvature/Topology --> Property --> Functionality in these technologically important geometries of carbons: nanotubes, fullerenes, nanorings, nanocones, nanohorns and nanodisks. To this end, we have determined the variation in first order high frequency Raman band which indicates a strong electron-phonon coupling. These concepts also apply to nanostructures of other "topological materials" such as BN nanotubes and nanotori, helical gold nanotubes as well as Möbius conjugated polymers. *This work is supported in part by ONR (SG) and DOE (AS). [1] S. Gupta et. al. Mater. Res. Soc. Symp. Proc. 863, Q6.3-Q6.9 (2005). [2] S. Gupta, R. J. Patel, N. Smith, Y. Y. Wang, R. E. Giedd, J. Mater. Res. (2006) (submitted). [3] S. Gupta and A. Saxena, Nano Letters (submitted, 2006).
9:00 PM - N9.8
Effects of P Content on Morphology of Nanocrystals Induced by FIB Irradiation in Ni-P Amorphous Alloy.
Koji Sato 1 , Chiemi Ishiyama 1 , Masato Sone 1 , Yakichi Higo 1
1 , Precision and Intelligence Laboratory, Tokyo Institute of Technology, Yokohama Japan
Show Abstract9:00 PM - N9.9
Characterization of Medium-range Order in Self-Assembled Organic-inorganic Hybrid by Fluctuation X-ray Microscopy.
Lixin Fan 1 , D. Paterson 1 4 , I. Mcnulty 1 , M. Treacy 2 , D. Kumar 2 , P. Du3 3 , U. Wiesner 3 , J. Gibson 1
1 Advanced Photon Source, Argonne National Lab, ARgonne, Illinois, United States, 4 , Australian Synchrotron, Clayton, Victoria, Australia, 2 Department of Physics and Astronomy, Arizona State University, Tempe, Arizona, United States, 3 Materials Science & Engineering, Cornell University, Ithaca, New York, United States
Show Abstract
Symposium Organizers
Ramki Kalyanaraman Washington University
Ugo Valbusa University of Genova
Zhenyu Zhang Oak Ridge National Laboratory
N10/LL6: Joint Session: Nanoscale Self Assembly by FIB: Theory and Applications
Session Chairs
Harley Johnson
Richard Langford
Wednesday AM, November 29, 2006
Room 209 (Hynes)
9:30 AM - **N10.1/LL6.1
Nanoscale Morphology Control Using Ion Beams.
Michael Aziz 1
1 Div. Engrg. & Appl. Sci., Harvard University, Cambridge, Massachusetts, United States
Show AbstractLow energy ion irradiation of a solid surface can be used to control surface morphology on length scales from 1 micron to 1 nanometer. Focused or unfocused ion irradiation induces a spontaneous self-organization of the surface into nanometer-sized ripples,dots, or holes; it also induces diameter increases and decreases in a pre-existing nanopore by a tradeoff between sputter removal of material and stimulated surface mass transport. Experiments will be reviewed that illuminate the kinetics of evolution of the surface morphological instability; the influence of initial and boundary conditions on guiding the self-organization; the development of shock fronts that sharpen features at sufficiently steep angles; and the kinetics governing the fabrication of nanopores for single-biomolecule detectors.
10:00 AM - N10.2/LL6.2
Surface Modification Energized by FIB: The Influence of Etch Rates & Aspect Ratio on Ripple Wavelengths.
Warren MoberlyChan 1
1 Chemistry and Materials Science, Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractIon beams have been used to modify surface topography, producing nanometer-scale ripples that have potential uses ranging from designing self-assembly structures, to controlling stiction of micromachined surfaces, to providing imprint templates for patterned media. Modern computer-controlled Focused Ion Beam tools enable alternating submicron patterned zones of such ion-roughened surfaces, as well as dramatically increasing the rate of ion beam processing. The DualBeam FIB/SEM also expedites process development while minimizing the use of materials that may be precious (Diamond) and/or produce hazardous byproducts (Beryllium). A FIB engineer can prototype a 3-by-3-by-3 matrix of variables in tens of minutes and consume only nanoliters of material; whereas traditional ion beam processing would require tens of days and tens of precious wafers. Saturation wavelengths have been reported for ripples on materials such as single crystal diamond or silicon; however this work exhibits wavelengths in excess of 400nm on diamond. Conversely, Be can provide a stable and ordered 2-dimensional array of <40nm periodicity. Rippling is not only a function of material, ion beam, and angle, but also is shown to be controlled by chemical environment, etch rate, and aspect ratio. Ideally a material exhibits a constant yield (atoms sputtered off per incident ion); however, pragmatic FIB processes, coupled with the direct metrological feedback in a DualBeam tool, reveal etch rates do not remain constant. Control of rippling requires controlled metrology, and robust software tools are developed to enhance metrology. In situ monitoring of the influence of aspect ratio and redeposition at the micron scale provide correlations to the rippling fundamentals that are controlled at the nanometer scale and by the boundary conditions of FIB processing.This work was performed under the auspices of the United States Department of Energy by the University of California, Lawrence Livermore National Laboratories under contract of No. W-7405-Eng-48.
10:15 AM - **N10.3/LL6.3
FIB Precise Prototyping and Simulation.
Philipp Nellen 1 , Victor Callegari 1 , Jurgen Hofmann 1 , Elmar Platzgummer 2 , Samuel Kvasnica 2
1 Electronics/Metrology, EMPA, Duebendorf Switzerland, 2 , IMS Nanofabrication GmbH, Vienna Austria
Show Abstract10:45 AM - N10.4/LL6.4
Formation and Ordering of Ga Droplet Arrays using Focused Ion Beam Irradiation.
Benjamin Cardozo 1 , Weifeng Ye 1 , John Mansfield 2 , Rachel Goldman 1
1 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Electron Microbeam Analysis Laboratory, University of Michigan, Ann Arbor, Michigan, United States
Show Abstract11:00 AM - N10/LL6:FIB
BREAK
11:30 AM - **N10.5/LL6.5
Focused Ion Beam Templating Of Epitaxial Growth.
Robert Hull 1 , Jennifer Gray 1 , Alain Portavoce 2 , Martin Kammler 3 , Frances Ross 4 , Jerry Floro 5
1 Materials Science, University of Virginia, Charlottesville, Virginia, United States, 2 , L2MP-CNRS, Marseille France, 3 , Infineon Technologies, Dresden Germany, 4 , IBM Research, Yorktown Heights, New York, United States, 5 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractWe show that focused ion beam (FIB) patterning of Si(100)surfaces can be used to control the subsequent nucleation of epitaxial Ge(Si) nanostructures. The interaction of FIB Ga ions with the Si surface modifies local topography, chemistry, crystallinity, strain and reactivity. We show how control of these phenomena allows arrays of nanostructures to be grown in patterns of arbitrary complexity with nanoscale precision in the location of each nanostructure.We describe two main approaches to these “nano-templating” methods. The first comprises growth of Ge quantum dots on FIB-modified Si(100) surfaces in a unique instrument that combines chemical vapor deposition, transmission electron microscopy and FIB sputtering in a UHV environment. In this configuration, we show that one Ge quantum dot (QD) can be localized to each FIB implant spot, under conditions where the ion dose within each feature is relatively low (~ 10e14 / cm2). At these low doses, less than a monolayer of Si is expected to be sputtered from each feature. However, we show that while surface chemistry and reactivity do affect the geometry and growth rate of the Ge quantum dots, it is a subtle surface topography that localizes the QD nucleation to the implant features. We observe that during post implant annealing (designed to recover surface crystallinity prior to epitaxial Ge deposition), a transient and subtle surface morphology appears within each feature, comprising a nanoscale annular depression ~ 0.5 nm deep that subsequently sharpens to a single pit and then disappears with further annealing. If the annealing is interrupted prior to disappearance of this topography, then QDs localize to the implanted features. If the topography disappears, then localization does not occur.In the second approach we localize “quantum dot molecules” (QDMs) into patterns of any desired symmetry. The QDM is a four-fold quantum dot structure bound by a central pit that occurs intrinsically during growth of GeSi/Si(100) heterostructures under conditions of limited adatom mobility, as we have previously reported. By patterning of Si(100) surfaces prior to surface cleaning and GeSi alloy deposition, the pits that nucleate each QDM can be individually positioned. The growth of the subsequent QDM array depends upon the pit dimensions, Si buffer layer thickness and GeSi alloy layer thickness and composition, but we demonstrate that we can effectively locate one QDM to each initial FIB pit.These approaches allow nanostructure arrays of any desired symmetry to be fabricated, with control over multiple length scales. This is key to exploring QD nanoelectronic architectures. This work also shows how the low throughput generally associated with FIB fabrication may be overcome by using the FIB for templating of subsequent growth, reaction or processing: in this example we can seed nanostructure growth sites at a rate of at least 10e4/sec.
12:00 PM - N10.6/LL6.6
Growth Mechanism of Indium Nanowire Induced by Focused Ion Beam Irradiation.
Do Hyun Kim 1 , Seung Soo Oh 1 , Hee-Suk Chung 1 , Euijoon Yoon 1 , Kyu Hwan Oh 1
1 School of Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of)
Show Abstract12:15 PM - N10.7/LL6.7
Self-Assembled Wrinkling on Polymer Substrates Induced by Focused Ion Beam Irradiation.
Myoung-Woon Moon 1 , SangHoon Lee 2 , Jeong-Yun Sun 2 , Kyu Hwan Oh 2 , Ashkan Vaziri 1 , John Hutchinson 1
1 Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 2 School of Material Sci & Eng, Seoul Natl Univ, Seoul Korea (the Republic of)
Show AbstractIn this presentation, we demonstrate a method to create self-assembled wrinkles on polymer substrates by focused ion beam (FIB) irradiation. The wrinkles were generated on confined surface areas of a flat polydimethylsiloxane (PDMS) upon FIB irradiation. The FIB of 30-keV gallium ion was rastered over rectangular regions with various areas, while the fluence of the beam was varied between 1013 and 1015 ions/cm2. Upon exposure of the PDMS to FIB, a stiff skin formed on the surface of the PDMS due to alteration in polymeric bonding. The tendency of this stiff skin to expand in the direction perpendicular to the direction of ion beam irradiation induces a compressive strain in the skin. The induced biaxial stress in the stiff skin leads to formation of wrinkles on the exposed area. We examined the chemical composition of the area exposed to FIB along depth using a TEM/EELS system to determine the composition and thickness of the generated stiff skin on PDMS. The induced stress, according to various ion fluences, is estimated by measurement of the wrinkling amplitude using Atomic Force Microscope. We studied the critical condition associated with the onset of surface wrinkling formation by changing the current and area of exposure. Various wrinkling patterns induced by FIB irradiation were explored including straight shape, herringbone and highly nonlinear hierarchical patterns.
12:30 PM - N10.8/LL6.8
Ion Beam Projection Techniques For Locally Modifying Phase Transformation Properties In Shape Memory Alloys.
Yves Bellouard 1 , Yogesh Karade 1 , Andreas Dietzel 1 , Wilhelm Bruenger 2 , Xi Wang 3 , Joost Vlassak 3
1 Mechanical Engineering, Eindhoven University of Technology, Eindhoven Netherlands, 2 ISIT, Fraunhofer Institute , Itzehoe Germany, 3 Division of Engineering and Applied Science, Harvard University, Boston, Massachusetts, United States
Show Abstract12:45 PM - N10.9/LL6.9
Fabrication of Sub-micron thick Solid Oxide Fuel Cells using a Focused Ion Beam.
Jeremy Cheng 1 , Hong Huang 2 , Fritz Prinz 2 1
1 Materials Science and Engineering, Stanford University, Stanford, California, United States, 2 Mechanical Engineering, Stanford University, Stanford, California, United States
Show AbstractSolid oxide fuel cells (SOFC’s) are high temperature electrochemical devices based on a ceramic, oxygen conducting electrolyte such as Yttria-stabilized Zirconia (YSZ). The conductivity of the electrolyte membrane as well as the performance of the electrode catalyst can be strongly affected by ion irradiation. Irradiation of the electrolyte with a high dose of ions such as Ar+ will produce a dense dislocation network with as many as 10^12 dislocations/cm^2. The irradiated region is limited to a depth of about 150nm from the surface of the electrolyte. In order to measure the effect of these dislocations on the oxygen conductivity, the electrolyte thickness must be on the same order of magnitude as the irradiation depth.
Furthermore, the conductivity changes from these dislocations may be difficult to distinguish from grain boundary effects in a polycrystalline material; ideally the electrolyte should be single crystal or an epitaxial thin film. YSZ can be deposited epitaxially onto a silicon substrate, but silicon diffuses readily into the YSZ forming a zirconate that precludes conductivity and fuel cell measurements.
A novel technique has been developed using a Dual-beam system to produce sub-micron, freestanding membranes from single-crystal material. In-situ Energy Dispersive Spectroscopy (EDS) was used to measure the membrane thickness and uniformity. The membranes were larger than 50x50 μm, pinhole free and gas-tight. Cells were tested both with and without a heavy dose of Ar ion irradiation. After membrane fabrication, a porous platinum catalyst was sputtered on both sides and the cells were run with pure H2 and air. Fuel cell I-V curves were measured as low as 300°C
N11: Self-assembly via Ion Implantation-Mechanisms
Session Chairs
Wednesday PM, November 29, 2006
Room 209 (Hynes)
2:30 PM - **N11.1
Shaping of Nanometals by High Energy Ion Beams.
Arjen Vredenberg 1 , Elmuez Dawi 1 , Martijn Mink 1 , Karl-Heinz Heinig 2 , Marcel Toulemonde 3 , Kai Nordlund 4 , Antti Kuronen 4
1 Debye Institute, Surfaces, Interfaces and Devices, Utrecht University, Utrecht Netherlands, 2 Inst. of ion beam physics and materials research , Research Center Rossendorf , Dresden Germany, 3 , Laboratoire CIRIL-GANIL, Caen France, 4 Accelerator Laboratory, University of Helsinki, Helsinki Finland
Show AbstractMetal nanorods and nanowires have great potential in a wide range of fields, because of their tunable (by shape and size) optical and magnetic properties. We present a new and unique way of producing nanorods and –wires, embedded in a solid, that are aligned in the same direction. Starting from spherical Au nanocolloids in a silica film we will show that the colloids are shaped controllably into rods and –at later stages- wires by irradiation with an MeV heavy ion beam. The ion-beam induced anisotropy (from a spherical colloid to a rod) is caused by the highly anisotropic ion track: a long, few nm diameter cylinder of highly excited material. The colloids elongate and form rods with their long axis in the direction of the ion beam. The mechanism of this deformation is still under investigation, but we will discuss possible origins, involving anisotropy in mechanical or mass balance gradients.We will also discuss the potential of these individually shaped nanoparticles in applications such as nano(bio-)sensors, upconverters for solar cells, magnetic nanodevices, smart optical materials with negative index of refraction (left-handed materials.
3:00 PM - N11.2
Ion-beam Processing and Size Control of Au Nanoparticles in Si-SiO2 Photonic Structures.
James Williams 1 , S. Charnvanichborikarn 1 , M. Conway 1 , C. Jagadish 1
1 RSPSE, Australian National University, CANBERRA, Australian Capital Territory, Australia
Show Abstract3:15 PM - N11.3
Nanostructuring SiO2/Si interfaces with a dense array of Sn or Pb metallic nano-islands
Felipe Kremer 1 , Joao Lopes 1 , Paulo Fichtner 2 1 , Fernando Zawislak 1
1 Instituto de Fisica, UFRGS, Porto Alegre, RS, Brazil, 2 DEMET, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
Show AbstractWe report on the formation of dense arrays of epitaxial Sn or Pb nano-islands at SiO2/Si(001) interfaces. The ionic species are room temperature implanted (fluences from 1 to 8E16 cm-2) within the oxide films and the islands are formed during thermal treatments at distinct temperatures T and times t (1173K≤T≤1373K, 1.8ks≤t≤21.6ks). We demonstrate that the Sn or Pb diffusion and accumulation at the SiO2/Si interface depends not only on the annealing temperature and time but also on the annealing atmosphere (N2 or high vacuum) and implanted fluence. For low annealing times and fluences we observe the formation of a high density of trapezoidal-like islands (d>7E11 cm-2) epitaxially oriented to the Si(001) substrate presenting a rectangular-like basis (2-6 nm in sides and 3-5 nm in high), flat tops and step edges. With increasing fluence the island density increases and, for 1373K and 21.6 ks, there is the formation of a bi-modal system presenting the small trapezoidal-like islands together with large lenticular-like structures (diameters about 30 nm and highs about 25 nm) half incorporated in the Si substrate. For intermediate times and fluences the island system presents a significant degree of order. These structures are of metallic phase and show a mean distance between particles smaller than their diameter. The formation of the islands is discussed in terms of the solubility and diffusivity properties of the atomic species and their size and shapes in terms of interfacial energy relations.
3:30 PM - N11.4
Self Assembled Patterns of Gold Nanoclusters in Silicon(100)Produced by Ion Implantation
Dinesh Kumar Venkatachalam 1 , Dinesh Sood 2 1 , Suresh Bhargava 1
1 School of Applied Sciences, RMIT University, Melbourne, Victoria, Australia, 2 School of Electrical and Computer Engineering, RMIT University, Melbourne, Victoria, Australia
Show AbstractSelf assembled gold nanoclusters are attractive building blocks for future nanoscale sensors and optical devices due to their exciting catalytic properties. Recently several methods have been employed to produce nanoclusters on solid substrates, which result in a random spatial distribution of the clusters. In this work, we have achieved ordered circular patterns of gold nanoclusters in Silicon (100) substrates by Au ion implantation followed by thermal annealing. Gold ions were implanted using a MEVVA (metal vapour vacuum arc) ion implanter. The lowest possible extraction voltage (10 kV) in the implanter to produce stable ion beam was chosen to maximise the surface concentration of implanted gold species. A metal (Al) mask with 16 equi-spaced circular holes each of 4 mm diameter was used in contact with the substrate held at room temperature to produce identical and well separated zones of gold ion implanted regions. Dose was varied from 1x1014 to 3x1016 Au ions/cm2. An open tube furnace was used for heating to form gold nanoclusters, using Argon (Ar) as carrier gas at atmospheric pressure. The temperatures of 600oC, 750oC, 1100oC were chosen on the basis of Au-Si phase diagram. After annealing, the samples were analysed using Scanning Electron Microscopy (SEM, Philips XL 30), Energy Dispersive X-ray Spectrometry (EDS, FEI QUANTA 200), and X-ray Diffraction (Bruker AXS, D8 GADDS). Upon annealing, the implanted gold diffuses, agglomerates and forms nanoclusters whereas the un-implanted region was devoid of such phenomenon. After annealing at 750oC for 60 min, ordered concentric circular patterns of Au nanoclusters (of size ranging from 16 to 500 nm) were observed. No such regular patterns were observed below Au ion fluences of 2x1016 cm-2. In order to understand the mechanism of formation of this unusual self assembled pattern, a systematic study of the growth and morphology of the nanoclusters was performed under carefully chosen conditions of ion dose and annealing (temperature, time and gas flow). The effect of presence of native oxide on Si substrates was also examined by dissolving it in 10% HF just prior to annealing in some control samples. No such pattern was observed when we implanted other ion species of Pd. Based on these experimental observations, a tentative model has been developed and is being tested: Au implantation produces an amorphous layer of silicon rich in Au; on annealing a thin layer of Au-Si eutectic liquid is formed; on solidification eutectic reaction may lead to formation of ordered circular pattern of Au rich nanoclusters in a matrix of Si which may be polycrystalline. When no eutectic liquid forms (e.g. below a critical threshold dose or temperature, or different species like Pd), the ordered pattern is not observed. This new process for self assembled ordered pattern of Au nanoclusters in Si may be very useful as a “seed” template for growth of “ordered” nanowires by vapour liquid solid growth techniques.
3:45 PM - N11:ImpFunda
BREAK
N12: Self-assembly via Ion Implantation - Applications
Session Chairs
Wednesday PM, November 29, 2006
Room 209 (Hynes)
4:15 PM - N12.1
Ion-Cut Synthesis: Nanostructures, Blisters, and Wafer Bonding.
Rachel Collino 1 2 , Da Mao 1 , Michael Thouless 1 2 , Rachel Goldman 1
1 Materials Science & Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show Abstract Ion implantation plus thermal annealing often leads to the formation and coalescence of gas bubbles which may be used as the basis for heterogeneous materials integration by means of transferring thin layers of one material onto another. For example, when an ion-implanted substrate is bonded to another substrate and subsequently thermally annealed, bubble formation and coalescence often lead to fracture of the original substrate just below the interface. To date, the sole role of implanted ions has been to induce the formation and coalescence of gas bubbles. We recently reported the formation and blistering of a layer of luminescent GaN-rich nanostructures, using N ion implantation into GaAs, followed by high temperature (>850°C) rapid thermal annealing [1]. These nanostructures apparently form at the position of maximum ion damage, while nitrogen gas bubbles form and coalesce near the interface between surface GaAs and GaAsN layers, pushing off a layer of nanostructured material. We are adapting this concept to achieve simultaneous nanostructure synthesis and layer transfer via wafer bonding, a process termed “ion-cut synthesis”. This process is expected to enable the development of low-cost manufacturing methods for heterogeneous nanostructure integration. To identify the optimal conditions for simultaneous nanocomposite synthesis and layer transfer in bonded heterostructures, we are investigating the formation of nanostructures and blisters, as well as methods for bonding GaAs to various substrates. To date, we have investigated blister formation in both doped and undoped GaAs implanted with a N ion dose of 5×1017 cm-2 and annealed at temperatures up to 850°C. Scanning electron microscopy reveals 2-4 μm diameter blisters with densities ranging from 2-4×106 cm-2. We will discuss quantitative atomic force microscopy studies of size and density distributions of nanostructures and blisters in N-implanted GaAs annealed at a variety of temperatures, in Ar or N2 gas ambients. In terms of GaAs wafer bonding, we have used a methyl silsesquioxane spin-on glass (SOG)-based GaAs-GaAs and GaAs-Si bonding method to achieve GaAs-alumina bonding. Our blade test measurements suggest that this SOG bonding method has increased the toughness of the GaAs-alumina interface. We expect that this will enable the relatively high temperature annealing required for ion-cut synthesis. We will also discuss ion-cut synthesis using both hydrogen and methyl silsesquioxane SOG bonding agents, and alumina and glass carrier substrates. This work was supported in part by NSF and UM Rackham Graduate School.[1] X. Weng, W. Ye, R.S. Goldman, and J.C. Mabon, J. Vac. Sci. Tech. B. 22, 989 (2004).
4:30 PM - N12.2
Fabrication of Nanostructures on Silicon Carbide using Ion-amorphization and Thermal Oxidation.
Sarit Dhar 1 2 , Ryan Davis 3 , Justin Gregory 2 , Leonard Feldman 1 2
1 Dept. of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee, United States, 2 Vanderbilt Institute of Nanosclale Science and Engineering, Vanderbilt University, Nashville, Tennessee, United States, 3 Dept. of Electrical Engg. and Computer Science, Vanderbilt University, Nashville, Tennessee, United States
Show Abstract4:45 PM - N12.3
The Role of Low Energy Ions in the Formation of Au clusters.
Petra Reinke 1 , James Howe 1 , Santhana Eswaramoorthy 1 , Elsa Thune 2
1 Materials Science and Engineering, University of Virginia, Charlottesville, Virginia, United States, 2 Insitute of Experimental and Applied Physics, University of Regensburg, Regensburg Germany
Show AbstractMetal clusters with a diameter of less than 10 nm are of considerable importance as building blocks in many nanotechnology applications. Ion assisted methods are well established in the synthesis of metal clusters and thin film materials and in general ions with energies of less than a few hundred eV dominate these processes. An important advantage in the use of low energy ions is the low level of damage. The focus of our study is to develop a fundamental understanding of the impact of ion energy, ion fluence and temperature on the size distribution of metal clusters. In the energy range between 350 and 20 eV the ion implantation depth decreases from a few atomic layers to two or three atomic layers. A mass selected ion beam facility was used to create an Au+ ion beam with a well-defined energy and a small energy width (îE<10 eV), which allowed us to systematically investigate the low energy regime. The Au clusters were analyzed with photoelectron spectroscopy and high-resolution transmission electron microscopy. A final state effect, which leads to cluster size dependent binding energy shifts in the photoelectron spectra, was used to analyze clusters in the size regime between 2 atoms and about 1.2 nm, while TEM afforded the assessment of the size distribution for larger clusters. Thin amorphous carbon films formed from 500eV C+ served as substrates and retained their microstructure during the subsequent Au implantation. The development of the cluster size distributions was observed as a function of (1) Au-ion energy, and (2) annealing temperature (up to 600 C). The mean cluster size decreases dramatically with increasing ion energy (from 5 nm at 20 eV implantation energy to a few atoms for 320 eV) while retaining a narrow size distribution. The implantation creates a sub-surface reservoir of Au atoms, whose extension and Au-concentration depends on the initial ion energy. Subsequent annealing leads to the appearance of new, small clusters, whose nucleation and subsequent growth is driven by Au-atoms from the sub-surface reservoir. Cluster ripening and an increase in mean cluster size is only observed at high temperatures and low ion energies, where surface processes dominate. The interplay between the different processes is described by a model, which includes the particle fluxes within the system, the Au-atom sinks and sources and the atom diffusion in the bulk and on the surface. The changes in the mean cluster size and the shape of the size distribution are successfully described within this framework. Control of the ion energy in the low energy regime allows to achieve relatively narrow cluster size distributions in a size regime, which is of considerable importance in nanotechnology applications. The development of a first model describing the relation between cluster size, ion energy and particle mobilities (temperature) is a critical step towards learning how to predict and tailor cluster size distributions.
5:00 PM - N12.4
Nano-graphitization in Amorphous Carbon Films via Electron Beam Irradiation and the Iron Implantation.
Eiji Iwamura 1 , Tatsuhiko Aizawa 1
1 Materials Science and Engineering, University of Toronto, Toronto, Ontario, Canada
Show Abstract5:30 PM - N12.6
Self-Assembly of Nanoparticle Precipitation Induced by Simultaneous Ion and Photon Irradiation.
Naoki Kishimoto 1 , Kenji Saito 2 1 , Jin Pan 2 1 , Oleg Plaksin 3 , Yoshihiko Takeda 1
1 Quantum Beam Center, National Insitute for Materials Science, Tsukuba, Ibaraki, Japan, 2 Dept. of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan, 3 , A. I. Leypunsky Inst. of Phy. and Power Eng., Obninsk, Kaluga region, Russian Federation
Show AbstractMetal nanoparticle composites are promising for ultrafast nonlinear optical applications, associated with surface plasmon resonance (SPR). Ion implantation arbitrarily injects immiscible atoms and locates nanoparticles within a certain depth. However, the lateral control of nanoparticles is difficult and has been limitedly succeeded with lithography, microbeam- or masked implantation. To control the nanoparticle arrangement, self-assembling mechanisms, if any, are demanded. In this paper, we explore nanoparticle patterning by combining laser and ion implantation.Photons were irradiated into SiO2, either sequentially or simultaneously with ion implantation. Ions of 60 keV Cu- or 3 MeV Cu2+ and photons of 532 nm or 355 nm were used to study effects on nanoparticle evolution. Optical properties of nanocomposites varied with photon energy and the total deposited energy. Sequential photon irradiation of 532 nm caused dissolution of Cu nanoparticles, whereas Cu precipitation was enhanced by sequential photons of 355 nm. The 532 nm-photons directly excite SPR of pre-existent nanoparticles and act as the nanoparticle eraser, whereas the 355 nm-photons, exciting defects or solute, tend to enhance precipitation. Contrarily, simultaneous photon irradiation of 532 nm acts as precipitation enhancement in SiO2. Systematic understandings of photon excitation effects enable us to self-assemble nanoparticles, by controlling photon irradiation.