bluuebunny/crossref_metadata_2025 huggingface dataset:
Incorporation and Role of Nitrogen During Oxynitridation of Silicon Studied by Photoelectron Spectroscopy
Authors: Suzuki Masayuki , Saito Yoji
Published: April 2011

We tried direct oxynitridation of silicon surfaces by remote-plasma-exited nitrogen and oxygen gaseous mixtures at 700°C in a high vacuum. The oxynitrided surfaces were investigated with in-situ X-ray photoelectron spectroscopy. With increase of the oxynitridation time, the surface density of nitrogen gradually increases, but that of oxygen shows nearly saturation behavior after the rapid increase in the initial stage. We also annealed the grown oxynitride and oxide films to investigate the role of the contained nitrogen. The desorption rate of oxygen from the oxynitride films is much less than that from oxide films. We confirmed that nitrogen stabilizes the thermal stability of these oxynitride films.
First-Principles Study of Vacancy-Assisted as Diffusion in Silicon
Authors: Xie Jianjun , Chen S.P.
Published: April 2011

A set of interaction potentials for vacancy-assisted As diffusion in silicon have been provided via first-principles pseudo-potential calculations. Some important reactions such as As+V ⇌ AsV, AsV + As ⇌ As2V, AsV + V ⇌ V2, as well as V + V ⇌ V2 are considered. The results demonstrate that the existence of another As atom greatly reduces the migration barrier of vacancy moving between the two As atoms and speeds up the diffusion of As. The AsV pair can attract another nearby vacancy. The binding force mainly comes from the binding between two vacancies, rather than from the AsV pair. The obtained potential energy diagrams provide input information for atomistic diffusion simulations.
Effect of Extended Defects on the Enhanced Diffusion of Phosphorus Implanted Silicon
Authors: Keys P. H. , Li J. H. , Heitman E. , Packan P. A. , Law M. E. , Jones K. S.
Published: April 2011

Extended defects resulting from ion implantation are believed to act in some cases as a driving force behind transient enhanced diffusion (TED). We use secondary ion mass spectrometry (SIMS) to study the diffusion enhancements of an underlying boron doped spike after creating implant damage in the near surface region. Diffusion enhancements are compared for silicon implants and phosphorus implants to distinguish between factors related to chemical species interactions versus those related to ion beam damage. Transmission electron microscopy (TEM) is used to investigate the existence and dissolution of extended defects. {311} extended defects are clearly visible in self-implanted samples but absent in phosphorus doped samples. The extended defects resulting from phosphorus implantation are small (20Å to 60Å diameter) “dot” defects barely resolvable by conventional TEM. methods. Despite the marked differences in defect morphology, diffusion enhancements in the boron marker layer are observable for both species. Results comparing the TED of a buried marker layer after P+ and Si+ show a larger overall effective diffusion length results after high dose (1x1014 cm−2) phosphorus implants. Visible defects in phosphorus implanted silicon are not the only source of TED, suggesting the existence of sub-microscopic phosphorus interstitial clusters (PIC). This provides important insight into the affect of phosphorus on TED.
In-Situ Observation of UV/Ozone Oxidation of Silicon using Spectroscopic Eli Psometry
Authors: Saitoh T. , Kobayashi D. , Kimura D. , Asai K.
Published: April 2011

Initial oxidation process of silicon in UV/ozone ambient has been monitored using a multi-wavelength, in-situ spectroscopic ellipsometry. Ozone gas was chemically formed by photochemical reaction of oxygen under ulUmviolet illuimination. The oxide growth was monitored for hydrogenated silicon surfaces as functions of oxygen gas flow rate, gas pressure and wafer temperature. Initial oxidation rates were very high at almost all the temperatures. The oxidation rate was 0.2 nm/min about ten times higher than that for thermal oxidation without UV light at low temperatures. The accelerated oxidation was probably due to an electric field effect on the oxidation of back-bond silicon by active oxygen atoms included in the ozone gas.
In Situ Diagnostics of Methane/Hydrogen Plasma Interactions with Si(100)
Authors: Duan H. L. , Bent Stacey F.
Published: April 2011

Methane/hydrogen plasmas have been reported to be sources both for a-C:H film deposition and for compound semiconductor etching. In this work, an in situ diagnostic study of methane/hydrogen plasma interactions with a silicon surface is carried out, focusing on the effect of hydrogen dilution. A remote electron cyclotron resonance (ECR) plasma using a H2/Ar mixture excites methane gas near a Si(l 00) substrate. In situ multiple internal reflection Fourier transform infrared (MIR-FTIR) spectroscopy is used to probe the surface species at different hydrogen dilution ratios. We find that at low methane pressure without hydrogen dilution, a-C:H films are deposited. With H2 dilution, the results suggests that some sputter/etching of the silicon surface occurs. Hence, methyl groups are identified as potential etchants for silicon materials. The data suggest that there is a competition between etching and deposition chemistry which depends strongly upon the methane pressure and hydrogen ratio in the plasma.
In-Situ Real-Time Ellipsometry Study of Dynamic Processes of YBa2Cu3O7−x Thin Films
Authors: Gao Y. , Mueller A.H. , Irene E.A. , Auciello O. , Krauss A.R. , Schultz J.A.
Published: April 2011

The optical absorption peak at 4. leV associated with oxygen deficiency in YBa2Cu3O7−x thin films was monitored by spectroscopic ellipsometry (SE) in real time during the growth process. Two regimes dominated by oxygen out- and in-diffusion have been observed during deposition by ion beam sputtering at 700°C.The effect of oxygen partial pressure during the post-deposition cooling process on the oxidation of deposited films has also been investigated. The thermodynamic stability of the grown films was examined by real time SE during post annealing process. In-situ SE measurements have been performed to obtain the dielectric function of oxygen deficient YBa2Cu3O6 films in the temperature range from 27°C to 700°C. It has been demonstrated that real time SE is a sensitive and useful technique for in-situ diagnostics of the dynamics of YBa2Cu3O7−x thin film processes.
Differential Anomalous X-Ray Scattering Techniques for Determination of Liquid and Amorphous Structures
Authors: Warburton W. K. , Ludwig K. F. , Wilson L. , Bienenstock A.
Published: April 2011

The differential anomalous scattering technique is outlined and compared to other techniques for studying short-range order in amorphous systems, such as EXAFS. The differential distribution functions obtained for liquid GeBr4 were found to support a model for the liquid state based on the structure of the h.c.p. crystal. Application of the technique to aqueous ZnBr2 also allowed discr imination between structural models.
An Atomic View of Surface Diffusion on Metals
Authors: Ehrlich Gert
Published: April 2011

Atomic migration in crystals is obscured by the crystal itself, and it has therefore taken ingenious indirect methods to study the diffusion process. In contrast, diffusion at surfaces is amenable to fairly direct examination, on the atomic level, through the use of the field-ion microscope. By combining measurements of the mean-square displacement with determinations of the distance distribution function, considerable detail about atomic jumps in diffusion can be obtained. Here we will briefly review results obtained by field-ion microscopic examination of single metal atoms and metal clusters diffusing on metal crystals.

What is noteworthy in the diffusion of single metal atoms is the variety of behavior which is dictated by the nature of the substrate, and the occasional complexity of the diffusion process. Examples of substrate-specific effects in atomic migration will be given for both fcc and bcc metals. Another surprising aspect of diffusion on metal surfaces is the role of clusters. These are stable at relatively high temperatures, and often diffuse at rates comparable to those of single atoms. The status of such cluster studies will be briefly examined, not only for their significance in surface transport, but also for their interest in understanding cohesion at metal surfaces.
1.55 Micron Emission from InAs/InP Self-Assembled Quantum Dots
Authors: Murray Ray , Bryan Caroline , Button Chris , Spikes D. , Hill G.
Published: April 2011

Self-assembled InAs/InP and InAs/InGaAsP quantum dots (QDs) grown by metal-organic chemical vapour epitaxy (MOVPE) exhibit emission at 1.5–1.6 μm at room temperature. P-I-N diodes incorporating a single InAs/InGaAsP QD layer exhibit strong electroluminescence over a wide range of input currents and emit significantly more light per layer than a InGaAs/InGaAsP multi-quantum well device.
Mid-Infrared Emission in InAs/GaAs Self-Assembled Quantum Dots
Authors: Boucaud P. , Sauvage S. , Brunhes T. , Glotin F. , Prazeres R. , Ortega J. M. , Thierry-Mieg V. , Lemaître A. , Gérard J. M.
Published: April 2011

We have investigated the emission properties of InAs/GaAs self-assembled quantum dots in the mid-infrared. The emission relies on the intraband transitions in the valence band of the quantum dots. We first show that third-harmonic generation can be observed. The frequency tripling efficiency is enhanced by the resonances between the pump excitation and the quantum dot intraband transitions. A giant third-order nonlinear susceptibility is measured for one dot plane. The narrow spectral dependence of the nonlinear susceptibility is well explained by simulations which account for the three-dimensional confinement potential. We secondly show that the mid-infrared spontaneous emission between hole confined states can be observed under an interband optical pumping. The spontaneous emission involves transitions between either the ground and excited states or between excited states. These measurements demonstrate the potentiality of self-assembled quantum dots for mid-infrared emission.
Lateral Coupling of Self-Assembled Quantum Dots Studied by Near-Field Spectroscopy
Authors: Robinson H.D. , Goldberg B.B. , Merz J.L.
Published: April 2011

Lateral coupling between separate quantum dots has been observed in a system of In0.55A10.45As self-assembled quantum dots. The experiment was performed by taking photoluminescence excitation (PLE) spectra in the optical near-field at 4.2 K. The high spatial resolution afforded by the near-field technique allows us to resolve individual dots in a density regime where interactions between neighboring dots become apparent. In the PLE spectra, narrow resonances are observed in the emission lines of individual dots. A large fraction of these resonances occur simultaneously in several emission lines, originating from different quantum dots. This is evidence of interdot scattering of carriers, which additional data show to be mediated by localized states at energies below the wetting layer exciton energy. A very rich phonon spectrum generated by the complicated interfaces between barrier and dot material is also evident in the data.
Oxide Film Formation on Metals and Alloys by Thermal, Electrochemical and Plasma Oxidation and Prediction of Resulting Structures
Authors: Cocke D. L. , Promreuk S. , Schennach R. , Mollah M. Y. , Naugle D. G.
Published: April 2011

Multicomponent oxide films are needed to meet the increasing demands of the electronics industry. Three main methods that involve oxidation of a metallic substrate are thermal, anodic and plasma oxidation. Today we do not have an adequate fundamental physical-chemical model of how multicomponent oxides evolve on alloys under these oxidizing conditions to design a wide range of materials for electronic devices. The three methods will be discussed in terms of physical/chemical parameters that influence the chemical nature and structure of the resulting oxides. By using surface studies of the oxidation behavior of numerous metals and alloys we have been able to delineate the factors which are most important to the oxide formation process and provide insight into the prediction of oxide layer structures. The electrochemical processes that occur during the materials reaction with a chosen environment will be used to discuss the physical and chemical mechanisms involved. Intrinsic and extrinsic electric fields will be shown to influence the chemical and structural nature of the resulting oxide structures. Examples will be presented from a number of metal and alloy systems that have been examined in our laboratory. These include Al, Ti, Zr, Nb, Mn, Cu and Ni and some of their selected alloys. The models that have developed from these studies are providing some predictive power in how the complex oxide overlayer will be chemically speciated and on its structure.
Ultraviolet Assisted Pulsed Laser Deposition of Thin Oxide Films
Authors: Craciun V. , Howard J. , Singh R. K.
Published: April 2011

The properties of Y2O3, ITO (indium tin oxide), and TaSi2 thin layers grown using a new in-situ ultraviolet (UV)-assisted pulsed laser deposition (UVPLD) technique have been studied. X-ray diffraction investigations showed that with respect to conventional PLD grown films under similar conditions, but without UV illumination, UVPLD grown films exhibited better crystallinity, especially for growth at low substrate temperatures, from 200 °C up to 450 °C, depending on the material. X-ray photoelectron spectroscopy investigations showed that UVPLD layers contained less physisorbed oxygen than the conventional PLD layers, exhibiting a better overall stoichiometry. These results suggest that during the ablation-growth process, UV radiation increases the surface mobility of adatoms and provides more reactive gaseous species. Both factors contribute to the crystalline growth and are especially effective at moderate processing temperatures, where the thermal energy available for the process is comparatively low.
Micromachined Array Studies of Tin Oxide Films: Nucleation, Structure and Gas Sensing Characteristics
Authors: Panchapakesan B. , DeVoe D. L. , Cavicchi R. E. , Walton R. M. , Semancik S.
Published: April 2011

The ability to fabricate sensitive and stable gas sensors which can detect low concentrations of gaseous species is necessary for many critical applications such as environmental safety monitoring. Although highly sensitive gas sensors have been produced by dispersion of catalytic metals on oxide sensing films, fouling of catalysts can cause instability in sensor performance. We have examined an approach which involves fine tuning the microstructure of tin oxide sensing films by vapor depositing an ultra-thin film of seed layer metals prior to tin oxide deposition. Metals including Fe, Sn and Pt have been investigated for their influence on tin oxide growth. Systematic studies of the growth mechanism and microstructure of CVD tin oxide using four-element arrays of “microhotplates” have revealed a number of different film morphologies which result from seeding. Enhancements in sensitivity for seeded growth relative to unseeded growth suggest a method of producing sensitive gas sensors which may not require the addition of surface catalytic layers. In this study we also demonstrate the use of microhotplates not only as sensing devices, but as excellent platforms for materials research.
Preparation of Na0.5K0.5NbO3/La0.6Sr0.2Mn1.2O3/LaAlO3 Thin Film Structures by Pulsed Laser Deposition
Authors: Cho Choong-Rae , Khartsev S. I. , Grishin A. M. , Lindbäick Ture
Published: April 2011

We report on ferroelectric/giant magnetoresistive Na0.5K0.5NbO3/La0.6Sr0.2Mn1.2O3 (NKN/LSMO) heterostructures grown onto LaAlO3 (001) single crystal using KrF pulsed laser ablation of stoichiometric ceramic target. Main processing parameters have been optimized to obtain smooth LSMO template layer, avoid NKN-LSMO interdiffusion, preserve NKN stoichiometry against the lost of volatile potassium and sodium and achieve reasonable reliability of NKN film performance. X-ray diffraction θ- 2θ scans and rocking curves evidence for single-phase content and high c-axis orientation both in template LSMO and top NKN layers. Ferroelectric measurements yield remnant polarization Pr of 1.5 [C/cm2 and spontaneous polarization Ps of 7 μC/cm2 at electric field strength of 130 kV/cm. At room temperature, dielectric permittivity ε′ and dissipation factor tan δ have been found to vary from 595 to 555 and 0.046 to 0.029 respectively in the frequency range of 0.4 to 20 kHz. At 10 kHz dielectric permittivity linearly increases from 410 to 650 in the temperature range 77 K to 415 K while the dissipation factor below 320 K does not exceed 3%.
Improvement of the Electrical Properties of YMnO3 Thin Films in A Metal/Ferroelectric/Si Structure
Authors: Yi Woo-Chul , Seo Chang-Su , Kwun Sook-Il , Yoon Jong-Gul
Published: April 2011

Highly (0001)-oriented films of YMnO3 were grown on n-type Si(100) substrates by a chemical solution deposition with a modified precursor solution. Spin-coated films were crystallized by rapid thermal annealing at 650 °C, and showed improved structural and electrical properties. Capacitance-voltage (C-V) measurements at 1 MHz showed a counterclockwise hysteresis, with a memory window of 1.9 V at 9 V, due to ferroelectric polarization, and a dielectric constant of 25. The effects of mobile ionic charge and effective interface charge in the C-V measurements were found to be small by investigating the bias sweep rate dependence and flat-band voltage shift, respectively. The interface trap density near the Si midgap was obtained to be about 1.3 × 1011 cm−2eV−1 through conductance measurements. Current-voltage characteristics showed a leakage current density of 16 nA/cm2 at 3 V. An asymmetric polarization-voltage (P-V) hysteresis curve became symmetric one with a remanent polarization value of 0.1 μ C/cm2 under He-Ne laser illumination. The depolarization field in the ferroelectric film and charge compensation by the light-generated minority carriers may be responsible for the observed P-V characteristics. The low temperature fabrication of this YMnO3 film showed good structural and electrical properties for application to nonvolatile ferroelectric memory devices.
Low Loss Ferroelectric Films Grown on Polycrystalline Ferrite Substrates for Dual-Tuning Microwave Devices
Authors: Jiang H. , Hu W. , Liang S. , Fouflyguine V. , Zhao J. , Jia Q. X. , Groves J. R. , Arendt P. , Vittoria C. , How H.
Published: April 2011

We successfully deposited high quality biaxially oriented BaxSr1-xTiO3 thin films on polycrystalline yttrium iron garnet substrates using both the metal-organic chemical liquid deposition and pulsed laser deposition methods with biaxially oriented MgO and yttriumstabilized- zirconia buffer layers. The dielectric losses of the films range from 0.005 to 0.015 while 25% of dielectric constant change was observed with 40V bias voltage up to 10 MHz. Both the dissipation and dielectric constant of the films remained nearly constants over a wide temperature range. A dual-tuning microwave phase shifter using a BST film grown on an MgO buffered polycrystalline YIG substrate was fabricated. A significant phase shift was observed in a wide frequency range when an electric bias or a magnetic field was applied to the device.
Metal-Organic Chemical Vapor Deposition of Metal Oxides: from Precursor Synthesis to Thin Films
Authors: Belot J. A. , Wang A. , Edleman N. L. , Babcock J. R. , Metz M. V. , Marks T. J. , Markworth P. R. , Chang R. P. H.
Published: April 2011

This contribution describes the synthesis, characterization, and implementation of new lanthanide and main group metal-organic chemical vapor deposition precursors based on the 2,2-dimethyl-5-N-2-methoxyethylimino-3-hexanonato ligand system. The new homoleptic, fluorinefree, low melting, and highly volatile complexes are ideally suited for oxide MOCVD, and in many applications are superior to standard β-diketonates while maintaining ease of synthesis and low cost. This is explicitly demonstrated by the growth of high quality CeO2/YBa2Cu3O7-δ multilayers.
Thin Film Dielectrics for Electronics Using Combustion Chemical Vapor Deposition
Authors: Lin Wen-yi , Huang Hai , Cullen D. Kacy , Shoup Shara S. , Cousins Donald , Schmitt Jerome J. , Hunt Andrew T. , Romanofsky Robert R. , VanKeuls Fred W. , Miranda Félix A. , Mueller Carl H.
Published: April 2011

This paper reviewed work to date on multicomponent oxides deposited, utilizing openatmosphere Combustion Chemical Vapor Deposition for electronic applications. Epitaxial barium strontium titanate and strontium titanate thin films were deposited on (100) MgO single crystal substrates. They were patterned to form interdigitated structures for electrically tunable devices, namely, coupled microstripline phase shifters (CMPS). The undoped, as-deposited perovskite dielectrics exhibited a figure of merit of 53°/dB at 20 GHz and 23°C, indicating high degree of tunability and fairly low loss. High-permittivity (ε=263), polycrystalline BST and SrTiO3 were studied for dynamic random access memory, and leakage current density of 10−7 A/cm2 was measured. Intended for non-volatile ferroelectric memory, lead zirconium titanate was deposited onto a seed layer of perovskite structure to prevent the growth of the unwanted pyrochlore phase. To function as buffer layers for superconductor applications, epitaxial CeO2, YSZ, SrTiO3, LaAlO3, Y2O3, and Yb2O3 coatings on single crystal and textured nickel substrate were investigated. Electronic analyses and characterization, using SEM, EDS, XRD, and X-ray pole figures, were presented.
The Electron-Hole Interaction and Linear Optical Constants
Authors: Benedict L. X.
Published: April 2011

We present an ab initio computational scheme to calculate ε(ω) including the screened electron-hole interaction. Results are presented for GaP and optically-pumped GaAs. We also discuss a time-dependent formulation which has some conceptual advantages.
First-Principles Calculations of Positron Annihilation in Solids
Authors: Barbiellini B. , Hakala M. , Nieminen R. M. , Puska M. J.
Published: April 2011

We present first-principles approaches based on density functional theory for calculating positron states and annihilation characteristics in condensed matter. The treatment of the electron-positron correlation effects (the enhancement of the electron density at the positron with respect to mean-field density) is shown to play a crucial role when calculating the annihilation rates. A generalized gradient approximation (GGA) takes the strong inhomogeneities of the electron density in the ion core region into account and reproduces well the experimental total annihilation rates (inverses of the positron lifetimes) by suppressing the rates given by a local density approximation (LDA). The GGA combined with an electron-state-dependent enhancement scheme gives a good description for the momentum distributions of the annihilating positron-electron pairs reproducing accurately the trends observed in the angular correlation (ACAR) or Doppler broadening measurements of the annihilation radiation. The combination of the present positron lifetime and momentum density calculations with the corresponding measurements yields a unique tool for defect identification. Especially, the investigation of various vacancy-type defects in semiconductors able to trap positrons will be an important field for these methods. We will show that the identification of vacancy-impurity complexes in highly n-Type Si and the study of the SiO2/Si interface are particularly interesting applications.
Initial Crystallization Reactions
Authors: Perepezko J.H. , Allen D.R.
Published: April 2011

During the initial stage of phase formation reactions nucleation conditions often apply a controlling influence on the phase selection, product phase number density and grain size. In most cases the operation of nucleation control is also associated with the development of significant undercooling or supersaturation in order to initiate crystallization. Under this constraint it is common to observe different forms of alloy metastability. In fact, a hierarchy of equilibria can be identified based upon the severity of the kinetic constraints that act during transformation. One consequence of the different levels of metastability is the development of precursor reactions before the initial crystallization. In other cases a kinetic competition between different reaction modes or structures can yield a change in the transformation pathway during reaction. The appearance of kinetic transitions is one consequence of the competition between concurrent reactions and provides a valuable opportunity for kinetics analysis and modeling. In cases where sequential reactions are separated by temperature or time intervals other kinetic constraints operate to expose metastability due to diffusional growth limitations. The identification of the reaction control provides the foundation for kinetics analysis and the development of alloy design strategies. These features can be considered in terms of the observed crystallization behavior during rapid solidification and solid state interface reactions.
Kinetic Limitations to Shape Equilibration of Liquid Pb Inclusions In Al
Authors: Gabrisch H. , Kjeldgaard L. , Værnholt Olesen A. , Johnson E. , Dahmen U.
Published: April 2011

The shape of liquid Pb inclusions in Al was investigated by in-situ electron microscopy over a temperature interval from 300 to 500°C. The inclusion shape was found to depend on size and temperature. During isothermal annealing after melting, small inclusions rounded off while larger inclusions remained faceted until the temperature was raised to about 500°C. During subsequent cooling, inclusions refaceted, although less strongly than during heating. The shape hysteresis between heating and cooling cycles was found to be due to the barrier of ledge nucleation necessary to advance the faceted interfaces. The observations show that the step energy depends on temperature and its disappearance at about 540-600°C indicates a roughening transition.
Coupling The Nano and Micro Scales In Modelling The Formation of Metallic Microstructures
Authors: Chirazi A. , Rafii-Tabar H.
Published: April 2011

We have developed a model of dendritic grain growth in the solidification process of metallic alloys in which the output of a nanoscopic molecular dynamics simulation, based on the use of many-body interatomic potentials, provides the input into the microscopic nucleation and growth model of Rappaz et al. The microscopic model itself is also extended by the introduction of a stochastic dynamics, via the Ito stochastic calculus, to account for the random fluctuations in the growth trajectory of the dendrite tip. The model is applied to the industrially important Sn-Pb alloy and its result is compared with that obtained with the Rappaz model.
Atomic Structure of Alloys Close to Phase Transitions
Authors: Van Tendeloo G. , Schryvers D.
Published: April 2011

Phase transitions are often accompanied by pre-transition effects. These effects have been studied on an atomic scale by high resolution electron microscopy. For the diffusion controled phase transitions we discuss short range ordering effects in Ni-Mo and Cu-Pd. For the displacive transitions we discuss the martensitic nucleation in Ni-Al and the nanoscale domain formation in the Ni-Ti R phase.
On The Effect of Au Addition and the Role of B on Nanocrystallization of Fe-Zr-B Amorphous Alloy
Authors: Zhang Y. , Wanderka N. , Czubayko U. , Zhu F. , Wollenberger H.
Published: April 2011

Using atom probe field ion microscopy (APFIM) we examined the local chemical compositions of Fe-7Zr-5B-lAu and Fe-14B amorphous alloys in the course of primary crystallization. Au rich clusters are formed during primary crystallization of Fe-7Zr-5B-lAu alloy. However, these clusters do not act as nucleation sites for α-Fe particles. In the early stage of primary crystallization, heterogeneities of Fe and B evolve in the amorphous phase. Heterogeneous distribution of B was found in the as-melt-spun Fe-14B amorphous alloy. During primary crystallization, B is highly supersaturated not only in the nanometer sized α-Fe particles in Fe-7Zr-5B-lAu alloy, but also in those of large diameters in Fe-14B alloy. From the results it is concluded that presence of B lowers the nucleation barrier for primary crystallization.
Diffusion Pathway of Interface Reactions in Amorphous-SiC/Ni
Authors: Dong Z.F. , Perepezko J. H. , Edelstein A.S.
Published: April 2011

A multilayer sample of amorphous SiC (α-SiC) and polycrystalline Ni was prepared by ionbeam sputtering, and was used as a model, prototype system to study the stability of metal contacts with SiC against interdiffusion reactions near the interface. The modulation wavelength is around 80 nm and with equal thickness of α-SiC and Ni layers. By use of XRD, TEM and energy dispersive spectroscopy (EDS), information on the structural evolution and composition distribution during heat treatment was obtained. The diffusion of Ni into the SiC layer, and Si and C into the Ni layer appears to take place concurrently during the annealing process. An amorphous reaction layer was formed during the heat treatment that is distinct from the α-SiC. The increase in thickness of the reaction layer followed a parabolic time dependence in the initial stage, until further reaction was limited by the precipitation of a graphite layer near the original α-SiC/Ni interface. A metastable intermediate phase and a NiSi phase were identified in the original Ni layer due to the diffusion of Si and C based on the decomposition of the α-SiC.
Thin Film Growth and Ion-Beam Modification: Md Simulations Going Beyond Simple Systems
Authors: Haddeman Edwin F. C. , Bunnik Bouke S. , Thijsse Barend J.
Published: April 2011

Molecular Dynamics computer simulations were used to explore a number of complex phenomena that occur during film growth and ion-surface interactions. A few examples are discussed. (1) Strong surface patterns develop when a Mo film is grown on a Mo(110) substrate, whereas they are absent for Mo on Mo(100). (2) Depositing a Mo film on a substrate containing two antiparallel (100)/(910) grain boundaries leads to complicated film morphologies in the grain boundary regions. Stresses, mosaic spread, and regions of fcc Mo are observed, and their stability is examined. (3) Cu films deposited on a Mo(110) substrate, a model system for interconnects in modern IC technology, are affected by the strong fcc/bcc interface mismatch. The Cu film properties are analyzed for thermally evaporated films and for films grown by argon ion-beam assisted deposition (IBAD).
Enhancement in the Growth of Textured HFCVD Diamond Coatings on Ti-6Al-4V Substrates by Excimer Laser Processing
Authors: Galeev Mikhail T. , Vedawyas M. , Sivanathan G. , Kumar Ashok
Published: April 2011

In this work we address the studies of enhancement in diamond growth on Ti-6AI-4V metal alloy by modifying the surface using the excimer laser ablation technique, prior to deposition of diamond. Ti-6Al-4V is chosen for its technological importance in aerospace industry, dental and bio-implant applications. Analysis of the structures of the film is done using X-ray diffraction, scanning electron microscopy and Raman spectroscopy. Ablation of the alloy by excimer laser pulses produces periodically hill/valley structures on the surface, thus increasing the density of diamond nucleation and film adhesion. The roughness of the alloy surface was measured to be in the 0.5μm – 1μm range with an average distance between peaks of the hill/valley structure measuring 1.5μm.
Deposition of Cubic-SiC Thin Films on Si (111) using the Molecular Ion Beam Technique
Authors: Matsumoto T. , Mimoto K. , Kiuchi M. , Sugimoto S. , Goto S.
Published: April 2011

SiC thin films were formed on Si (111) at growth temperatures of 750–1000 °C using the molecular ion beam technique, with a precursor of methylsilicenium ions (SiCH3+). The chemical bindings and surface structures of SiC thin films were analyzed by Raman spectroscopy and reflection high-energy electron diffraction. As a result, 3C-SiC (111) was grown on Si (111) substrates without carbonized treatments.
Ain Thin Films Prepared by Reactive Ion Beam Coating
Authors: Cheng L. L. , Yu Y H. , Sundaravel B. , Luo E. Z. , Lin S. , Lei Y M. , Ren C. X. , Cheung W. Y. , Wong S. P. , Xu J. B. , Wilson I. H.
Published: April 2011

Aluminum Nitride (AIN) is a promising material for a variety of technological applications because it has many exceptional properties, such as wide band gap (WBG) and negative electron affinity (NEA). AIN thin films were prepared by Reactive Ion Beam Coating. The properties of the AIN thin films may be a function of one of the preparation conditions: the beam energy. We used the non-Rutherford backscattering (non-RBS) and Auger Electron Spectroscopy (AES) results to analyze the composition of the AIN thin films. Atomic Force Microscopy (AFM) was applied to study the morphology of films. On the other hand, electron field emission properties were also studied to find the relationship between the compositional, morphological and electron field emission properties of the AIN thin films.
Modification of Thin Film Growth using Glancing-Angle Ions
Authors: Barnett Scott A. , Ruthe Kurt C. , Deluca Paul M.
Published: April 2011

This paper reviews the use of glancing-angle ions for modifying surfaces and thin film growth processes. Ions impinging on a flat surface at oblique incidence angles are mostly reflected without penetrating, providing very low sputtering rates along with minimal damage and implantation. They also provide a unique selectivity, where ion energy is coupled to defects or rough portions of the surface, while flat portions are essentially unaffected. This allows one to clean contaminated surfaces and smoothen rough surfaces, with little or no ion damage. In addition, recent results indicate that the ion energy couples directly to adatoms during epitaxial growth of GaAs(001). This was observed by a decrease in the time required for diffusion across terraces on a vicinal GaAs surface, as the glancing-angle Ar ion current was increased. It was also found that ion-enhanced diffusion shifted the growth mode from two-dimensional island nucleation to step-flow growth, and resulted in flatter growth surfaces. Finally, glancing-angleions can be used to introduce biaxial texture into polycrystalline GaAs films.
Characterization of the Interface Between Lanthanum Hexa-Aluminate and Sapphire by Exit Wave Reconstruction
Authors: Wessler B. , Steinecker A. , Mader W.
Published: April 2011

Epitaxial thin films of rare-earth hexaaluminates on basal plane sapphire have been produced by chemical solution deposition. LaAl11O18 films with magnetoplumbite structure grow with (0001)HA||(0001)S and [1100]HA||[2110]s orientation relationship

To investigate the stucture of the interface exit wave reconstruction of focus series was carried out using a field emission TEM. Due to the inversion of the imaging process major artefacts at the interface can be eliminated. Exit waves were simulated based on different interface models and were compared with the reconstructed waves to localize the positions of the atoms at the interface. Two different types of interfaces were observed in the samples. One of the types, in which the spinel block of hexaaluminate faces the sapphire with the mixed cation layer with occupied octahedra and tetrahedra, is characterized in detail. Face-sharing of coordination polyhedra is avoided to large extent
Structural Study of a [100] 45° Twist Plus 7.5° Tilt Grain Boundary in Aluminium by HREM
Authors: Shamsuzzoha M. , Deymier P. A. , Smith David J.
Published: April 2011

A [100] 45° twist plus 7.5° tilt grain boundary in aluminium prepared by cold rolling and annealing has been studied by high-resolution electron microscopy. The direct interpretability of the image features in terms of atomic column positions allows structural models of the grain boundary to be developed. The boundary exibits a high concentration of steps due to the 7.5° tilt from a perfect [100] 45° quasiperiodic misorientation. Occurrence of co-incidence and pseudo co-incidence of atomic planes across the interface appears to play an important role in the formation of steps along this boundary. Local relaxation of atoms resulting from the perturbation of the [100] 45° twist bi-crystal determines the boundary structure
Atomic Structure of Gold and Copper Boundaries
Authors: Hetherington C.J.D.
Published: April 2011

A very thin bicrystal film, prepared by depositing gold onto a {111} germanium substrate, then annealing and removing it, has been studied by HREM. The crystals grow predominantly in the orientations {111} and (111) which are related by a 60° rotation (Σ3 CSL) and bounded by {121} facets. In contrast to the boundaries studied in thicker films, these {112} facets extend through the depth of the film. Another crystal within the film also had a {111} orientation, but rotated by around 20° from the other crystals. A short length of boundary was found that was edge-on, symmetrical, facetted on (213) planes, and corresponding to Σ;7 (or Σ;21). A copper 1111 film did not show edge-on boundaries

The rigid body translation across the facets were measured and found to vary depending on the proximity to facet junctions. An expansion at the boundary was the general case
Bonding in Ion-Implanted Carbon Films Characterized by TEM Spectrum Lines and Energy-Filtered Imaging
Authors: Bentley J. , Walter K.C. , Evans N.D.
Published: April 2011

Ion-implanted diamond-like carbon (DLC) films have been characterized by techniques based on electron energy-loss spectrometry using an imaging energy filter on a 300kV TEM. Nitrogen implantation results in increased sp2 bonding and a 1.3 eV shift to higher binding energies for carbon-K. Argon implantation results in a smaller increase in sp2bonding with no detectable binding energy shift. The fraction of implanted species retained is much smaller for Ar than for N. Differences in behavior between N- and Ar-implanted DLC are consistent with expected chemical reactions. Preliminary results demonstrate the feasibility of mapping the Φ*/σ* intensity (sp2/sp3) ratio by energy-filtered TEM as an alternative to spectrum imaging in STEM mode
Surface Sensitivity Effects With Local Probe Scanning Auger-Scanning Electron Microscopy
Authors: Agterveld D. T. L. Van , Palasantzas G. , Hosson J.Th.M. De
Published: April 2011

Ultra-high-vacuum segregation studies on in-situ fractured Cu-Sb alloys were performed in terms of nanometer scale scanning Auger/Electron microscopy. S contamination leads to the formation of Cu2S precipitates which, upon removal due to fracture, expose pits with morphology that depends on the precipitate size and shape. Local variations of S and Sb distributions inside the pits were correlated to local surface orientations as Atomic Force Microscopy analysis revealed.
Hydrogen Storage in Single-Walled and Multi-Walled Carbon Nanotubes
Authors: Lee Seung Mi , Frauenheim Thomas , Elstner Marcus , Hwang Yong Gyoo , Lee Young Hee
Published: April 2011

We performed density-functional calculations to search for adsorption sites and predict maximum hydrogen storage capacity in carbon nanotubes. Our calculations show that the storage capacity of hydrogen, limited by the repulsive forces between H2 molecules inside nanotubes, increases linearly with tube diameters in single-walled nanotubes, whereas this value is independent of tube diameters in multi-walled nanotubes. We predict that H storage capacity in (10,10) nanotubes can exceed 14 wt % (161 kg H2/m3).
Hydrogenated Amorphous Carbon Deposition by Saddle-Field Glow Discharge
Authors: Zukotynski S. , Gaspari F. , Manage D. , Pletnev V. , Sagnes E.
Published: April 2011

The saddle-field glow discharge is modeled and electron multiplication and energy spectra are presented. The roles of the ion substrate current and ion energy at the substrate on the growth rate, hydrogen content, sp2 content and energy gap are discussed and the effects of atmospheric aging and high temperature annealing are described.
Nanocrystalline and Hard, Boron-Alloyed Be Coatings
Authors: Jankowski A. , Ramsey P. , McKernan M. , Morse J.
Published: April 2011

Boron-alloy coatings can be formed by sputtering compound targets, through co-deposition with other elemental targets, by utilizing reactive gas mixtures, and/or by post-deposition implantation. Specific to this study, boron-alloy coatings are assessed with respect to composition as deposited by co-sputtering boron and beryllium. Transmission electron microscope (TEM), bright-field images with selected area diffraction are used to reveal the microstructure and phase. Refinement in grain size to the nanoscale occurs through boron addition as well as transition metal impurities. An increase in coating hardness with boron addition is measured using nanoindentation. Scanning electron microscope (SEM), secondary electron images reveal the surface morphology variations for thick coatings that occur with boron addition as measured using energy dispersive spectrometry (EDS). The phase formed in boron-alloyed beryllium coating is found to be dependent on both coating composition and the sputter deposition conditions. It is concluded that the geometry of the deposition sources with the configuration of the substrate effect the coating composition, microstructure, and properties
Effects of CF4 Addition on the Growth of Amorphous CNx Films by Plasma Decomposition of CH4-N2 Gas Mixtures
Authors: Inokuma T. , Matsumoto H. , Kurata Y. , Hasegawa S.
Published: April 2011

Hydrogenated amorphous carbon nitride (α-CNx:H) films are deposited at 50–300°C by radio-frequency plasma decomposition of CH4-CF4-N2 gas mixtures. Effects of fluorine radicals on the deposition rate, composition, and on chemical bonding are investigated. When CF4 gas is added as partial replacement of CH4 gas, the deposition rate at 200°C steeply increases with increasing flow rate ratio RCF = [CF4]/([CH4]+[CF4]) up to ∼0.3, and then it decreases gradually. It is found that the nitrogen content, x, increases from 0.22 to 0.46 when RCF increases from 0 to 0.75. The inclusion of fluorine atoms into the films is less than 5 at%. The infrared absorption spectra shows strong enhancement of the absorption bands related to various forms of C—N bonding by the CF4 addition. It is found that the addition of CF4enhances the formation of C–N bonds in PECVD α-CNx:H films.
Structural and Electronic Characterization of Epitaxially-Grown Ferroelectric Vinylidene Fluoride Oligomer Thin Films
Authors: Ishida K. , Noda K. , Kubono A. , Horiuchi T. , Yamada H. , Matsushige K.
Published: April 2011

The structural and electric properties of newly synthesized vinylidene fluoride (VDF) oligomer thin films evaporated on various substrate were investigated. The structural behavior of the VDF oligomer thin films strongly depended on the kinds of substrate and substrate temperature during film preparation. In particular, the VDF oligomers epitaxially grew on KBr(001), aligned their molecular chain along the <110> direction of substrate surface, and were similar to polar Form Itype crystals of poly(VDF). While, the thin films evaporated on NaCl(001), SiO2/Si were non-polar Form II-type or mixture of both Form I- and Form II-type crystals with their molecular chain normal to the surface. These facts indicated that crystal field of substrate, based on van der Waals and electrostatic interactions, strongly influenced to ferroelectric phase transition of the VDF oligomer. In addition, we demonstrate the formation of the local polarized domains in the epitaxial crystals by applying electric pulses from a conducting AFM probe used as a positionable topelectrode, and confirm their piezoelectricity of the VDF oligomers for the first time.
Electrostrictive Grafr Elastomers and Applications
Authors: Su J. , Harrison J. S. , Clair T. L. St. , Bar-Cohen Y. , Leary S.
Published: April 2011

Efficient actuators that are lightweight, high performance and compact are needed to support telerobotic requirements for future NASA missions. In this work, we present a new class of electromechanically active polymers that can potentially be used as actuators to meet many NASA needs. The materials are graft elastomers that offer high strain under an applied electric field. Due to its higher mechanical modulus, this elastomer also has a higher strain energy density as compared to previously reported electrostrictive polyurethane elastomers. The dielectric, mechanical and electromechanical properties of this new electrostrictive elastomer have been studied as a function of temperature and frequency. Combined with structural analysis using x-ray diffraction and differential scanning calorimetry on the new elastomer, structure-property interrelationship and mechanisms of the electric field induced strain in the graft elastomer have also been investigated. This electroactive polymer (EAP) has demonstrated high actuation strain and high mechanical energy density. The combination of these properties with its tailorable molecular composition and excellent processability makes it attractive for a variety of actuation tasks. The experimental results and applications will be presented.
A Study of Liquid Crystalline Elastomers as Piezoelectric Devices
Authors: Biggs A. G. , Blackwood K. M. , Bowles A. , Dailey S. , May Alison
Published: April 2011

Ferroelectric liquid crystalline polymer films exhibit a number of unique physical properties and have been extensively studied during the last few years. Ferroelectric polymer films exhibiting a high level of piezoelectric activity would provide a new route to piezo- and pyro-electric sensors.

We report the fabrication of free-standing ferroelectric liquid crystal films which exhibit piezoelectric coefficients up to 4.4pC/N. We also report the investigation of the physical properties of these films by dynamic mechanical analysis.
A conductive composite film by permeation method
Authors: Wang Jin Wei , Srinivasan M. P.
Published: April 2011

A new method of making conductive composite films by permeation of the conducting guest species into the host is reported. A layer of poly(3-n-dodecyl thiophene) (P3ddt) is embedded at the surface of polyimide by permeation of the monomer or polymer (in solution in tetrahydrofuran or chloroform) into a solution of polyamic acid in n-methyl pyrrolidinone or dimethyl acetamide. The resulting composites were imidised and polymerized (if necessary). Chemical imidisation yielded composite -films that retained the conducting polymer even when the composite was subjected to solvent extraction. The films were conductive upon doping with iodine and recovered conductivity when they were exposed to iodine vapor subsequent to thermal de-doping. Thermogravimetry showed that the amount of thiophene incorporated into the polyimide was higher for permeation of the polymer than that of the monomer; however, the amount of p3ddt incorporated by the latter method was still higher than the amount that could be incorporated by blending polyamic acid with p3ddt. The levels of conductivity and speed of recovery for doped films were also higher for the permeated films. Results of scanning electron microscopy suggested that the higher mobility afforded by contact in the liquid state have contributed greater entanglement between the constituents leading to higher thermal and solvent resistance of the conducting constituent. The permeation method could be adopted to form composite films in solvent systems that are not completely miscible.