bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strain Measurements of Sigec Heteroepitaxial Layers On Si(100) Using Ion Beam Analysis
Authors: Sego S. , Culbertson R. J. , Ye P. , Hearne S. , Xiang J. , Herbots N. , Atzmon Z. , Bair A.E. 
Published: April 2011

AbstractThe strain in SiGeC heteroepitaxial films grown on Si(100) substrates has been quantified using ion channeling. The films were grown both by combined ion beam and molecular beam epitaxy (CIMD) and chemical vapor deposition (CVD). Rutherford backscattering spectrometry (RBS) was used to quantify the Ge concentration as well as the film thickness, nuclear resonance elastic ion scattering was used to quantify the carbon concentration, and ion channeling was utilized to measure film quality. Channeling angular scans across an off normal major axis were used to quantify the strain. Part of the film was removed by using a solution of HF, HN03 and CH3COOH in order to obtain a reliable scan in the substrate. The results indicate that C may be compensating for the strain introduced by Ge.
Directional Sputter Deposition for Semiconductor Applications
Authors: Rossnagel S.M. 
Published: April 2011

AbstractThe deposition of metal and compound films from ions rather than neutrals allows a high degree of control over the incident particle's direction and energy. Metal-rich plasmas have been produced using large magnetrons (30 cm dia., 20 kW) and in-flight ionization of the sputtered atoms by means of a dense, inductively coupled rf plasma. This plasma is generated by a multi-turn antenna inside the chamber located between the cathode and the sample. The nature of the deposition, including the ion-to-neutral ratio and the ion energy are controllable. Relative ionization of the metal has been measured at over 80%. Ion energy is controlled by a negative dc sample bias. Metal films of Cu and AlCu have been deposited on 200 mm Si wafers at room temperature into moderate aspect ratio wafer features with no voids. The features used are trenches and vias of width >3500A, and the technique has also been used to fill 2-level, “dual damascene” features. The films are highly (111) oriented and have low stress and low Ar content. The effects of ion direction as well as resputtering of the film topography are readily observed, and are consistent with computer model predictions. High quality TiN films (40 micro-Ohm-cm, gold colored) have also been deposited at room temperature into trenches and vias for applications as diffusion barriers.
Deposition of Diamond-Like Carbon (DLC) With Picosecond Laser Pulses
Authors: Qian F. , Singh R.K. , Dutta S.K. , Pronko P.P. 
Published: April 2011

AbstractWe have deposited unhydrogenated diamond-like carbon (DLC) thin films by laser ablation of graphite, using a high power Ti: Sapphire solid state laser system. DLC films were deposited onto single crystal silicon substrates at room temperature with picosecond laser pulses, at peak power densities in the 5x1011- 8x1012W/cm2range. A variety of techniques, including scanning and transmission electron microscopy (SEM and TEM), Raman spectroscopy, spectroscopic ellipsometry (SE), and electron energy loss spectroscopy (EELS) have been used to analyze the film quality. Smooth, partially transparent films were produced, distinct from the graphite target. Sp3volume fractions were found to be in the 50 - 60% range, with optical bandgaps ranging from 0. 6 to1. 2 eV, depending on the laser power density.
Tem Observation of the Damages in Heavily Ion-Implanted Fine Si Columns
Authors: Shingubara S. , Sukesako H. , Kawasaki T. , Inoue K. , Matusi Y. , Sakaue H. , Takahagi T. , Horiike Y. 
Published: April 2011

AbstractSi nanometer structures are promising for exhibiting the quantum size effect at temperatures even as high as a room temperature. The present work investigates by TEM the damages induced by a heavy ion-implantation to the fine Si columns, aim of fabrication of 1-D tunneling PN diode in future. Si columns are fabricated by electron beam lithography and reactive ion etching, followed by thinning by thermal oxidation of Si . Ultra fine Si column with a diameter of 8 nm are successfully formed. TEM lattice image observations for fine Si columns, which are subject to ion-implantation and subsequent annealing, are carried out. In the case of heavy doping of As, as well as BF2, as-doped structure is amorphous, and recrystallization is observed after annealing at 1000 °C for 30 min. Typical damages such as dislocations which are parallel to the {111} planes and Si micro-crystals which are differently oriented from the Si single crystal substrate are observed for Si columns with diameters larger than 40nm. However, it should be noted that no damage is observed for fine Si columns with diameters less than 20nm. It is suggested that defects are diffused out to the surface or the Si/SiO2 interface for ultra fine Si columns during annealing.
Characteristics of Excimer-Laser-Crystallized Polysilicon Films by Line Beam Scanning Method
Authors: Min Jhon Young , Hwan Kim Dong , Chu Hong , Woo Lee Chang , Sam Choi Sang 
Published: April 2011

AbstractCharacteristics of polysilicon films, crystallized by excimer laser annealing, have been investigated. The entire amorphous silicon film of 50 mm X 50 mm has been crystallized by scanning a line shape excimer laser beam, which basically reduces the nonuniformity in the beam overlap region of the 2-dimensional scanning method. The laser beam had a Gaussian profile in the scanning direction, which ensured good crystallization by the reversible transitions between the crystalline and amorphous states and was expected to give step annealing effect The laser energy density and substrate temperature were varied.
Flat-Top Polygonal Temperature Profiles by Laser Beams
Authors: Lu Y.F. 
Published: April 2011

AbstractA method was proposed to generate flat-top polygonal temperature distributions in substrates from a Gaussian-shaped laser source. The original Gaussian beam is equally and diametrically separated into several portions and is then rearranged so that the each portion has its peak intensity allocated toward outside. This can be realized by a symmetrical multi-facet prism. A mathematical model was derived to calculate the temperature rise induced the rearranged portions of the laser beam. Flat-top polygonal temperature profiles with two, three, four and six corners have been investigated by numerical calculations. It is shown that flat-top polygonal temperature distributions can be obtained by this method if the distance between the peaks of the beam portions is arranged to be certain proportions to the original Gaussian beam. It is also found the shape of the temperature profile is almost with the same size as the original Gaussian beam size and does not depend on the incident laser power and the substrate material.
Hydrogen Ion Beam Processing of Single Crystal Diamond Chips
Authors: Kiyohara Shuji , Miyamoto Iwao 
Published: April 2011

AbstractIn order to apply ion beam etching with hydrogen ions to the ultra-precision processing of diamond tools, hydrogen ion beam etching characteristics of single crystal diamond chips with (100) face were investigated. The etching rate of diamond for 500 eV and 1000 eV hydrogen ions increases with the increase of the ion incidence angle, and eventually reaches a maximum at the ion incidence angle of approximately 50°, then may decrease with the increase of the ion incidence angle. The dependence of the etching rate on the ion incidence angle of hydrogen ions is fairly similar to that obtained with argon ions. Furthermore, the surface roughness of diamond chips before and after hydrogen ion beam etching was evaluated using an atomic force microscope. Consequently, the surface roughness after hydrogen ion beam etching decreases with the increase of the ion incidence angle within range of the ion incidence angle of 60°.
Composition and Structure of Zirconium Nitride Films Produced by Ion Assisted Deposition
Authors: Valizadeh R. , Colligon J.S. , Donnelly S.E. , Faunce C.A. , Park D. , Kheyrandish H. 
Published: April 2011

AbstractThe growth mechanism of ZrNx films produced by reactive ion beam sputtering with or without concurrent low energy ion bombardment of argon or nitrogen has been investigated. The effect of substrate temperature in the range of 300-680K, partial pressure of nitrogen and ion/atom arrival rate on the composition and microstructure of the films have been studied. RBS analysis has confirmed that the nitrogen content varies over wide range 0-60 at. %, depending on the nitrogen/zirconium arrival rate, and the ion assist flux but it is independent of the ion assist energy. TEM analysis shows that the films are non-columnar and polycrystalline with grain sizes l-15nm which depend on the nitrogen content and the deposition temperature.
In-Situ Electron Microscopy Studies of The Behavior of Metal Particles on Ceramic Substrates
Authors: Terry R. , Baker K. , Rodriguez Nelly M. 
Published: April 2011

AbstractThis paper is devoted to a discussion of how the information derived from the application of in-situ transmission electron microscopy can be used to gain a unique insight into the manner by which various factors dictate the morphological characteristics of metal particles on a variety of ceramic substrates. In this context, we have used the technique to examine the influence of the strength of the metal-support interaction on the mode of sintering of small particles, and how the chemical nature of the gas environment can induce significant changes in the shapes of the metal particles in a given system. Attention is also focussed on the wetting behavior of metal particles dispersed on graphite when reacted in oxygen and how this aspect impacts on their subsequent mode of catalytic attack.
Effect of Surface Structure on The Adsorption of CO(II) on ∝-Al2O3: A Glancing Angle Xafs Study
Authors: Towle Steven N. , Bargar John R. , Brown Gordon E. , Parks George A. , Barbee Troy W. 
Published: April 2011

AbstractGlancing-angle x-ray absorption fine structure (XAFS) spectroscopy has been used to characterize the structure of Co(II) complexes adsorbed from aqueous solution on single crystal ∝-Al2O3 surfaces. The spectra reveal considerable differences in the local structure, as a function of both the crystallographic face and the orientation of the sample with respect to the beam polarization. Data analysis indicates that the predominant mode of Co chemisorption is as a tridentate CoO6 octahedral complex edge-shared with surface Al octahedra. For systems where this method is feasible, it is the technique of choice for characterizing metal ion adsorption complexes.
Electron Microscopy Studies and Image Simulation of the YBa2Cu3O7−x/ BaF2 Interface
Authors: Lee J. L. , Silcox J. 
Published: April 2011

AbstractImages of the YBa2Cu3OT7−x (YBCO) / BaF2 interface obtained with a scanning transmission electron microscope (STEM) show a relatively wide (∼40 Å) band of contrast at the interface, despite attempts to orient the interface plane parallel to the beam. Simulation of STEM annular dark field (ADF) images of several different interface geometries suggests that strain is the dominant cause of this wide band of contrast at the interface. In particular, it is the dislocations which run normal to the beam direction which make a significant contribution to the width of the contrast band in the case of this YBCO / BaF2 interface. A line scan taken across the interface using energy dispersive X-ray spectrometry (EDX) suggests that there is no significant Ba concentration at the interface, indicating that Z-contrast is not the primary contrast mechanism in these ADF images of the YBCO / BaF2 interface.
Influence of Internal Interfaces on the Dielectric Properties of Ceramic Microwave Resonators
Authors: Davies Peter K. 
Published: April 2011

AbstractThe structures of all the prominent ceramic dielectric resonators have been found to exhibit extensive inhomogeneity. This structural disorder arises from the formation of extended defects, polytype intergrowths or variable degrees of cation order. For the systems involving a cation order-disorder reaction, e.g. ZrTiO4 and Ba(Zn1/3Ta2/3)O3, the formation of internal interfaces can have a pronounced effect on the dielectric properties. In the absence of secondary dopants the lattice strains associated with the interfaces increase the dielectric losses by as much as two orders of magnitude. However, the contributions of the interfaces can apparently be controlled, and perhaps eliminated, by introducing selected dopants that segregate and stabilize the local boundary regions.
Direct Correlation of Transport Properties and Microstructure In Y1Ba2Cu3O7-x Thin Film Grain Boundaries
Authors: Vuchic B. V. , Merkle K. L. , Buchholz D. B. , Chang R. P. H. , Marks L. D. 
Published: April 2011

AbstractIndividual 45° [001] tilt grain boundaries in Y1Ba2Cu3O7-x thin films grown on biepitaxial substrates were studied. The thin films were grown using both pulsed organometallic beam epitaxy (POMBE) and laser ablation. Transport characteristics of the individual grain boundaries were measured including resistance - temperature (R-T) and current - voltage (I-V) dependencies with and without an applied magnetic field. In order to elucidate possible structural origins of the differences in transport behavior, the same grain boundaries which were electrically characterized were subsequently thinned for electron-microscopy analysis. Transmission-electron-microscopy and high-resolution-electron-microscopy were used to structurally characterize the grain boundaries. The macroscopic and microscopic structures of two boundaries, a nominally resistive and a superconducting grain boundary, are compared.
First Principles Calculations for Metal/Ceramic Interfaces
Authors: Finnis M. W. , Kruse C. , SchÖnberger U. 
Published: April 2011

AbstractWe discuss the recent first principles calculations of the properties of interfaces between metals and oxides. This type of calculation is parameter-free, and exploits the density functional theory in the local density approximation to obtain the electronic structure of the system. At the same time the equilibrium atomic structure is sought, which minimises the excess energy of the interface. Up to now calculations of this type have been made for a few model interfaces which are atomically coherent, that is with commensurate lattices. Examples are Ag/MgO and Nb/Al2O3. In these cases it has been possible to predict the structures observed by high resolution electron microscopy. The calculations are actually made in a supercell geometry, in which there are alternating nanolayers of metal and ceramic. Because of the effectiveness of metallic screening in particular, the interfaces between the nanolayers do not interfere much with each other.Besides the electronic structure of the interface, such calculations have provided values of the ideal work of adhesion. Electrostatic image forces in conjunction with the elementary ionic model provide a simple framework for understanding the results.An important role of such calculations is to develop intuition about the nature of the bonding, including the effects of charge transfer, which has formerly only been described in an empirical way. It may then be possible to build atomistic models of the metal/ceramic interaction which have a sound physical basis and can be calibrated against ab initio results. Simpler models are necessary if larger systems, including misfit dislocations and other defects, are to be simulated, with a view to understanding the atomic processes of growth and failure. Another area in which ab initio calculations can be expected to contribute is in the chemistry of impurity segregation and its effect at interfaces. Such theoretical tools are a natural partner to the experimental technique of high resolution electron energy loss spectroscopy for studying the local chemical environment at an interface.
Simulation of Segregation to Interfaces in Metal-Oxides
Authors: Battaile C. , Najafabadi R. , Srolovitz D.J. 
Published: April 2011

AbstractSegregation of isovalent cation impurities to (001) and (011) free surfaces in (Co0.3Ni0.7)O and (Fe0.12Mn0.88)O was investigated using atomistic computer simulations. Impurity concentrations were represented by a mean-field approximation, and equilibrium distributions of impurities were calculated by minimization of the free energy. Surface energy effects were found to dominate segregation behavior, even when in competition with misfit strain energy effects. These Free Energy method predictions compared well with more accurate Monte Carlo simulations, suggesting that the mean-field representation of impurity concentration is satisfactory for this application.
High Resolution Transmission Electron Microscopy of Metallic Film/Laser-Irradiated Alumina Couples.
Authors: Pedraza A. J. , Cao Siqi , Allard L. F. , Lowndes D. H. 
Published: April 2011

AbstractA near-surface thin layer is melted when single crystal alumina (sapphire) is pulsed laserirradiated in an Ar-4%H2 atmosphere. γ-alumina grows epitaxially from the (0001) face of axalumina (sapphire) during the rapid solidification of this layer that occurs once the laser pulse is over. Cross sectional high resolution transmission electron microscopy (HRTEM) reveals that the interface between unmelted sapphire and γ-alumina is atomistically flat with steps of one to a few close-packed oxygen layers; however, pronounced lattice distortions exist in the resolidified γ-alumina. HRTEM also is used to study the metal-ceramic interface of a copper film deposited on a laser-irradiated alumina substrate. The observed changes of the interfacial structure relative to that of unexposed substrates are correlated with the strong enhancement of film-substrate bonding promoted by laser irradiation. HRTEM shows that a thin amorphous film is produced after irradiation of 99.6% polycrystalline alumina. Formation of a diffuse interface and atomic rearrangements that can take place in metastable phases contribute to enhance the bonding strength of copper to laser-irradiated alumina.
Characterization of the Thin Oxide-Nitride-Oxide (ONO) Structure Using Spectroscopic Ellipsometry
Authors: Asinovsky Leo M. , Zierer Steve 
Published: April 2011

ABSTRACTSpectroscopic ellipsometry has been used to characterize thin oxide/nitride/oxide (ONO) layer structures. Films were deposited on top of the Si/oxide/polysilicon filmstack using a low-pressure chemical vapor deposition (LPCVD) technique. Different approaches to modeling this structure are compared to select an adequate representation. Analysis of the data for the three-layer-with-abrupt-interfaces ONO model using an effective-medium or Cauchy approximation shows strong correlation of the parameters and ambiguity of the results. A more robust and physically plausible model of the ONO structure as an inhomogeneous oxynitride film with Gaussian distribution of the silicon nitride component is suggested. This interpretation of the ONO structure is supported by the results of Auger electron spectroscopy (AES) and transmission electron microscopy (XTEM).
Use of Quantum-Well Superlattices to Increase the Thermoelectric Figure of Merit: Transport and Optical Studies
Authors: Hicks L. D. , Bi X. X. , Dresselhaus M. S. 
Published: April 2011

ABSTRACTThe thermoelectric figure of merit (ZT) of a material is a measure the usefulness of the material in a thermoelectric device. Presently, the materials with the highest ZT are Bi2Te3 alloys, with ZT ≃ 1. There has been little improvement in ZT for over 30 years. So far, all the materials used in thermoelectric applications have been in bulk form. Recently, however, calculations have shown that it may be possible to increase ZT of some materials through the use of quantum-well superlattices. We have made preliminary measurements on the Bi/PbTe superlattice system using transport and optical techniques to determine whether it is possible to achieve such an increase in ZT.
A New Method for Preparing Ge Nano-Crystallites Embedded in SiNY Matrices
Authors: Chen Kunji , Qu Xuexuan , Huang Xinfan , Li Zhifeng , Feng Duan 
Published: April 2011

ABSTRACTWe report a new method for synthesizing Ge nano-crystallites embedded in SiNy film matrices. On the basis of the effect of the reactant precursors and preferential chemical bonding of Si-N and Ge-Ge, thin films with Ge clusters embedded in SiNy matrices have been prepared in the PECVD system with reactant gases of SiH4, GeH4 and NH3 mixed in the hydrogen plasma. The as-deposited films were then crystallized by Ar ion laser annealing or thermal annealing technique to form nanometer-sized Ge crystallites.The composition and microstructures of these new type of sample were characterized by infrared absorption spectra, transmission electron microscopy, X-ray diffraction and Raman scattering spectra. The results indicated that the average size of Ge crystallites was estimated to be 2-20 nm depending on the deposition and annealing parameters and can be controlled by a designed manner.
Synthesis, Structural Characterization, and Optical Spectroscopy of Close Packed CdSE Nanocrystallites
Authors: Kagan C. R. , Murray C. B. , Bawendi M. G. 
Published: April 2011

ABSTRACTWe describe a method to synthesize optical quality thin and thick films of close packed CdSe nanocrystallites (quantum dots). The average dot size is tunable from ∼12-150 Å in diameter with ∼3.5% rms size distribution. The identity of each particle and the high monodispersity of the sample are maintained in the films as revealed by small-angle x-ray scattering, transmission electron microscopy, and optical spectroscopy. We use small-angle x-ray diffraction patterns to obtain form factors for the individual dots and to generate radial distribution functions for the densely packed films. We observe the random close packing of dots in the solid state using transmission electron microscopy. Comparing optical spectra of particles close packed in a film with those of nanocrystallites dispersed in alkanes reveals similar optical resonances in absorption while the emission lineshape is modified and its position is red shifted. Differences in film emission are consistent with electronic energy transfer between close packed dots within the inhomogeneous distribution of the sample.
Resonant Raman Scattering in CdSxSe1−x Nanocrystals: Electron-Phonon Coupling
Authors: Silvestri M. , Hwang L.W. , Persans P. , Schroeder J. 
Published: April 2011

ABSTRACTWe report pressure and laser tuned Raman scattering studies on CdSxSei1-x nanocrystals. The electron-phonon coupling strength was determined as a function of pressure beyond the bulk phase transition pressure point. The coupling strength at atmospheric pressure determined from the Stokes shifted photoluminescence and resonant Raman scattering is not drastically smaller than the bulk value as might be expected theoretically. As a function of pressure it also shows no abrupt changes at the bulk phase transition pressure point. These results indicate that deep traps play a critical part in the mechanism of the electron-phonon coupling.
Quantum Confinement Effects on 100–400 Å Diameter Silver Bromide Microcrystals
Authors: Ilana Freedhoff Michal , McLendon George , Marchetti Alfred 
Published: April 2011

ABSTRACTPrevious work on quantum confined AgBr microcrystals has been limited to either large (500-1000 Å diameter) aqueous samples or extremely small (60-100 Å diameter) inhomogeneously sized micellar samples. This has prevented an investigation of the effect of size restriction on the phonon assisted transitions of the indirect exciton. A non-aqueous preparation was developed, capable of providing more homogeneous size distributions of AgBr microcrystals in the 100-400 Å diameter range. Low temperature luminescence studies were performed to determine the changes in energy and intensity associated with these excitonic transitions. The radiative lifetimes of some of the excitonic processes were measured in order to obtain a more global perspective on the photophysics of AgBr.