bluuebunny/crossref_metadata_2025_split huggingface dataset:
Description of the Atomic Positions Around Interfacial Ledges in Terms of the Somigliana Dislocation Model
Authors: Bonnet R. , Loubradou M. 
Published: March 2011

ABSTRACTIn many materials, crystalline interfaces are facetted. The experimental evidence is that on each side of an interfacial ledge, or along the facets meeting along a common line, low energy atomic structural units are preserved which accommodate elastically angular or/and length misfit(s). Each facet can be considered as a Somigliana dislocation (SD) whose core is extended on the facet. The elastic displacement field of a SD is derived in an anisotropic continuum, for any orientation of the facet relative to a given Cartesian frame. From an atomic point of view, the translation state of the two crystals on each side of the facet is defined. The dislocation content attached to a ledge or a dihedral angle formed by two joining facets along a common side is also analyzed. The local elastic field related to these cases are derived and applications are presented for depicting the positions of the atomic columns in theoretical plots. Comparisons are made with some other theoretical works and HRTEM images. Examples illustrate the application of the Somigliana model to grain boundaries in hexagonal crystals (Mg, WC), and an interphase interface Ni3AI/Ni3Nb.
The Stabilization of Face-Centered-Cubic Titanium
Authors: Jankowski Alan F. , Wall Mark A. 
Published: March 2011

ABSTRACTThe artificial layering of metals can change both physical and structural characteristics from the bulk. The stabilization of such phases often occurs when the component layers are constructed on a nanometric scale. The sequential layering of nickel and titanium has produced the formation of a previously unreported, face-centered-cubic (f.c.c.) phase of titanium.
Effect of Yb Diffusion Barriers on the Properties of In/ n-Hg1−xCdxTe Contacts
Authors: Leech Patrick W. , Reeves Geoffrey K. , Li Yuan H. , Kibel Martyn H. 
Published: March 2011

ABSTRACTThe effect of incorporating a Yb diffusion barrier on the electrical and interfacial properties of In/Hg1−xCdxTe contacts has been examined. Measurements of the specific contact resistance, pc, as a function of Yb layer thickness were performed for a series of semiconductor compositions from x = 0.32 to 0.65. Large changes in pc were evident only at x 0.56 and above a Yb thickness of 2.5nm to 6.0nm, this critical level of layer thickness decreasing with x-value. Analytical examination of the interfaces by Auger electron spectroscopy, secondary ion mass spectroscopy and Rutherford backscattering spectrometry has shown a progressive reduction in the extent of In indiffusion with increasing thickness of the Yb interlayer.
The Effect of Grain Boundary Chemistry on the Slip Transmission Process Through Grain Boundaries in Ni3Al
Authors: Robertson I. M. , Lee T. C. , Subramanian Raja , Birnbaum H. K. 
Published: March 2011

ABSTRACTThe conditions established in disordered FCC systems for predicting the slip system that will be activated by a grain boundary to relieve a local stress concentration have been applied to the ordered FCC alloy Ni3Al. The slip transfer behavior in hypo-stoichiometric Ni3Al with (0.2 at. %B) and without boron was directly observed by performing the deformation experiments in situ in the transmission electron microscope. In the boron-free and boron-doped alloys, lattice dislocations were incorporated in the grain boundary, but did not show evidence of dissociation to grain boundary dislocations or of movement in the grain boundary plane. The stress concentration associated with the dislocation pileup at the grain boundary was relieved by the emission of dislocations from the grain boundary in the boron-doped alloy. The slip system initiated in the adjoining grain obeyed the conditions established for disordered FCC systems. In the boron-free alloy, the primary stress relief mechanism was grain-boundary cracking, although dislocation emission from the grain boundary also occurred and accompanied intergranular crack advance. Because of the importance of the grain boundary chemistry in the models for explaining the boron-induced ductility in hypo-stoichiometric Ni3Al, the chemistry of grain boundaries in well-annealed boron-doped and boron-free alloys was determined by using EDS. No Ni enrichment was found at the grain boundaries examined. These observations are discussed in terms of the different models proposed to explain the ductility improvement in the boron-doped, hypo-stoichiometric alloy.
TEM and HREM Investigation of The Precipitation of Cobalt and Nickel In Polycrystalline Silicon
Authors: Möller H. J. , Chung Juyong , Huang Lan 
Published: March 2011

ABSTRACTThe precipitation behavior of cobalt and nickel at grain boundaries in multicrystalline silicon is investigated. The metals are diffused into the specimens from a surface source between 800 -1000 °C and the precipitation after cooling is studied by conventional and high resolution TEM. Cobalt and nickel disilicide precipitates nucleate both in the bulk and at grain boundaries. They form few large (micrometer size) plate-like or three-dimensional precipitates depending on the cooling rate. Cobalt disilicide with a slightly larger lattice mismatch has a higher tendency to nucleate at large angle grain boundaries. Both suicides nucleate preferentially at coherent twin boundaries forming a few atomic layers thick platelet parallel to the {111} twin plane. HREM and image simulations are performed to analyze the Si / MS12 / twin interface structure (M = Co, Ni).
Comparison Of Thermally- And Irradiation-Induced Grain Boundary Segregation In Austenitic Stainless Steels
Authors: Kenik Edward A. 
Published: March 2011

ABSTRACTSegregation at grain boundaries in austenitic stainless steels sensitized by either thermal annealing or irradiation was studied by analytical electron microscopy. Characterization of grain boundary compositions in both types of materials was performed by high spatial resolution (≥2 nm) X-ray microanalysis. Whereas similar chromium depletion is observed in both processes, there are differences in the behavior of the other alloying elements and in the mechanisms responsible for the segregation. In thermal sensitization, the nickel/iron ratio and the silicon level observed at grain boundaries are similar to those for the matrix. In cases where little or no precipitation occurs, co-segregation of phosphorus, chromium, and molybdenum occurs at boundaries and interfaces. For radiation sensitization, radiation-induced segregation (RIS) results in enrichment of nickel, silicon, and, in certain cases, phosphorus and in depletion of iron at grain boundaries. There appears to be some synergism between segregation of nickel and silicon, which increases the magnitude of RIS effects. Grain boundary precipitation is often observed in both thermally- and irradiation-sensitized materials. However, the nature and origins of the two types of precipitation are different. The formation of chromium-enriched grain boundary carbides is the cause of the chromium depletion in thermal sensitization. In contrast, the precipitates produced by irradiation are enriched in nickel and silicon and depleted in chromium relative to the matrix and therefore are the result of RIS. Results for thermal- and radiation-induced segregation in manganese-stabilized austenites are compared to that for nickel-stabilized austenites.
Atomistic Simulation of Void Formation in ic Metal Interconnects
Authors: Nandedkar A. S. , Srinivasan G. R. 
Published: March 2011

ABSTRACTWe present an atomistic model to study void formation in aluminum interconnects in integrated circuit (1C) chips. Aluminum single and bicrystals were studied with various concentrations of vacancies and strain levels. It was found that either vacancies or tensile strains could lead to void formation. It will be shown that the void formation can be prevented by maintaining compressive strains in the computational cells.
Possible Mechanism Of The Stress Evolution And Point Defects Generation During The Solid Phase Epitaxial Silicide Growth.
Authors: Italjantsev A. G. , Kuznetsov A.Yu. 
Published: March 2011

ABSTRACTIn this paper we present a model of nonequilibrium point defect generation in the silicon substrate during solid state reactions of the surface suicides formation, resulting from the interaction between the substrate and the thin metal film. The model is based on the following principles. The local stress, which is appearing during each act of the suicide molecule (MexSiy) creation at the suicide - silicon interface, relaxes by the generation of ηv point defects. The point defect generation rate (m is the suicide growth rate) has been defined by the mininimization of the system free energy AG, which includes the enthalpy of chemical reaction ΔG the value of the relaxed elastic energyμ is the silicon shear modulus, Ω = (xΩMe+yΩSi) is the combined volume of metal and silicon atoms with stoichiometric coefficients, ΔΩ = (ΩMexSiy - Ω), ΩV is the vacancy volume in the matrix; and the term ΔGd = ηVkTln(C/C0) which takes into account the energy of the solid solution of noninteracting point defects, where C° is an equilibrium vacancy concentration and C is the real vacancy concentration. The estimations show that there is not any essential thermodynamic force which may prevent stress relaxation for any reasonable point defect supersaturation. For this case point defect generation rate may be written as jV = m(ΔΩ/ΩV). For the reactions of the initial phase formation in the Me-Si structures the values of ΔG*el, ηV and jV have been calculated and it has been shown that vacancy concentration can reach the values of 1015 - 1016 cm-3 at the regions nearest to the interface even during initial low temperature stages of the Ni, Pt, Cr suicide formation with the metal atoms are predominant moving species.
Synthesis and Characterization of Mo(Ta)/MoSix Microlaminates
Authors: Kung H. , Vyletel B. M. , Ghosh A. K. 
Published: March 2011

ABSTRACTVapor phase synthesis approaches were employed to produce laminated microstructures with high temperature phases alternated with ductile phase layers for toughness enhancement. Microlaminates of alternating layers of Mo and cosputtered Mo-Si were deposited on a Si substrate using direct current (DC) and radio frequency (RF) sputtering technique. Microstructural evolution and phase formation after diffusion annealing (900°C, 2 hr) was evaluated using cross-sectional transmission electron microscopy (TEM). Heat treating the microlaminates resulted in the growth of a Mo3Si interface phase between Mo and cosputtered layer and conversion of the amorphous cosputtered layer into crystalline Mo5Si3. A higher Si/Mo ratio in the cosputtered layer caused the formation of dispersed Mo5Si3 grains in Mo layer. The residual stress state was measured by monitoring the curvature change of the microlaminates using a laser beam. By decreasing the bilayer thickness to 1/3, the residual stress is reduced by ∼50%.
Evolution of Structure with Fe Layer Thickness in low Dimensional Fe/Tb Multilayered Structures
Authors: Harris V. G. , Aylesworth K. D. , Elam W. T. , Koon N. C. , Coehoorn R. , Hoving W. 
Published: March 2011

ABSTRACTThe atomic structure of a series of low-dimensional Fe/Tb multilayered structures has been explored using a conversion-electron, extended x-ray absorption fine structure (EXAFS) technique. A structural transition from a close-packed amorphous structure to a body-centered crystalline structure is detected to occur over an Fe layer thickness range of 12.5 Å to 15.0 Å (Tb thickness is held constant at 4.5 Å). Magnetic properties, specifically, magnetization, anisotropy field, and Kerr rotation angle, are measured and found to change significantly in response to this transition. Exploitation of the polarization properties of synchrotron radiation allowed for the description of the atomic structure both perpendicular and parallel to the sample plane.
Dynamics and Atcmic Strujciure of Martemite-Austenite Interfaces :
Authors: Chen S. , Clapp P. C. , Rifkin J. A. 
Published: March 2011

ABSTRACTThe structure of the lowest energy interface between an hcp austeidte phase and an foc martensite phase of similar atomic volumes has been simulated by annealing a disordered region between the two perfect lattices until semi-coberent intergrowth occurred. The two structures were oriented so that the closepacked planes were parallel, and closepacked directions were aligned. The dynamics of this interface and the structure which it evolved as it moved was then studied by applying a transformation driving force through the use of an Embedded Atar Method potential. Initially the interface moved in a reconstructive, diffusive manner but eventually it developed a highly mobile, diffusionless form which moved at about one third of the shear sound velocity. The structure of this rapidly moving interface could be analyzed in terms of three different types of Shockley partials arranged in sequence, but passing at slightly different times. This structure agrees with some elements of a model previously proposed by Christian to describe the transformation in pure Co, and agrees with other elements of a proposal of Mcbreer, Lunggren and Franck to explain their observations of the transformation in 4He. Neither fully explain our observations.
Characterisation of Interfaces in SiGe Superlatrlces by Combined Grazing Incidence X-Ray Fluorescence and Reflectivity
Authors: Powell Adrian R. , Bradler Jaroslav , Thomas Charles R. , Kubiak Richard A. , Keith Bowen D. , Wormington Matthew , Hudson John M. 
Published: March 2011

ABSTRACTX-Ray reflectivity enables the determination of interface and surface roughness along with the variations present in the electron density. Total reflection X-ray fluorescence allows surface analysis with high sensitivity and quantification. By use of grazing angle x-ray fluorescence taken simultaneously with the reflectivity measurements, over a range of angles near the critical angle, it is possible in principle to produce a depth profile of each element, with a composition sensitivity of 0.0002%. A silicon-germanium single layer was used to calibrate the instrument and a Si-Ge 5- period superlattice for a demonstration measurement.
Interface Reactions in Bilayers of Aluminum and Nickel-Chromium Alloy
Authors: Heald S. M. , Tan Zhengquan , Jayanetti J. K. D. 
Published: March 2011

ABSTRACTGlancing angle EXAFS and x-ray reflectivity are used to study the interface reaction between nickel-chromium alloys and aluminum. The two metals are found to react independently with Al, with the first reactions taking place at temperatures similar to those found for the pure metals. This means that Ni reacts first with Al to form NiAl3, leaving behind a Cr-rich region at the interface. In this Cr-rich region some of the Cr transforms to the bcc structure from the fcc form of the alloy. At higher temperatures Cr reacts to form CrAl7, and there is no evidence for ternary compound formation. Samples were also prepared with a controlled O contamination at the interface, and it inhibits the reaction much the same as for the pure metal cases. The Ni reaction is not identical to the pure sample case, since the presence of Cr slows down the reaction, and inhibits the initial reaction in the as-prepared bilayers.
Structural Properties Of Co/Re Superlattices
Authors: Huai Y. , Cochrane R. W. , Shi Y. , Fischer H. E. , Sutton M. 
Published: March 2011

ABSTRACTThe structures of equal-thickness Co/Re multilayer films and several Co/Re bilayer films have been investigated by X-ray diffraction at low and high angles. Analysis of low-angle reflectivity data from bilayer films indicates that interfacial intermixing is limited to three monolayers and that the two interfacial configurations are different. The high-angle X-ray diffraction data show that multilayer films have coherent interfaces and a highly textured structure with hep [002] orientations normal to the film plane for periods 21 Å ≤ Λ ≤220 Å. Detailed structures have been determined by fitting the X-ray spectra to calculated ones using a trapezoidal model. The results indicate that samples with 42 Å≤ Λ ≤220 Å have relatively sharp interfaces, in good agreement with the bilayer results. In addition, an out-of-plane expansion of the Co (002) layer is observed in samples with large Λ and results from structural disorder leading to a reduced atomic density. For Λ <21 Å the interfaces arise from the rougher surfaces of the deposited layers.
Determination Of Intermetallic Formation Mechanism Using Differential Scanning Calorimetry Of Multilayered Thin Films
Authors: Schlesinger T. E. , Prokes S. M. , Cammarata R. C. 
Published: March 2011

ABSTRACTThe ability to determine which growth mechanism (interface-reaction-rate-limited vs. diffusion-limited) of intermetallic formation by interfacial reactions using differential scanning calorimetry (DSC) is demonstrated. Suicide formation in multilayered thin films of chromium and amorphous silicon was chosen as a model system. It is shown that suicide formation in this system followed a linear rate law corresponding to an interface-reaction-rate-limited growth mechanism. An activation energy and pre-exponential for the rate constant were determined.
A Comparison Of The Corrosion Behaviour Of Nanocrystalline And Normal Crystalline Nickel
Authors: Rofagha R. , Langer R. , El-Sherik A. M. , Erb U. , Palumbo G. , Aust K. T. 
Published: March 2011

ABSTRACTThe effect of grain size on the corrosion behaviour of nickel in 2N sulphuric acid is evaluated by potentiodynamic testing and characterization of the corrosion morphology for grain sizes ranging from 100μ to 32nm. The influence of the grain boundary component on key electrochemical parameters (free corrosion potential, passivation current density and potential, transpassive dissolution rate) is discussed.
Interface Structure Of Iron Oxide Thin Films Grown On Sapphire And Single-Crystal MgO
Authors: Anderson Ian M. , Tietz Lisa A. , Barry Carter C. 
Published: March 2011

ABSTRACTThe ability to tailor thin film interface structure is illustrated by the growth of thin ferric oxide films using different deposition parameters. Low-pressure chemical vapor deposition (CVD) has been used to grow α-Fe2O3 on sapphire while pulsed-laser ablation (PLA) followed by low temperature oxidation has been used to grow γ-Fe2O3 on MgO. The structure of the films and of the film-substrate interfaces has been characterized using transmission electron microscopy (TEM) and selected-area diffraction (SAD) in plan view. The different deposition techniques lead not only to the growth of two different polymorphs of ferric oxide but also to different growth mechanisms and film-substrate interface structures. In addition, changes in the thermodynamic conditions during deposition can give rise to different interface structures between the individual structural domains of the film.
High Resolution Electron Microscopy Of Intercalated Phases In The Y-Ba-Cu-0 System
Authors: Burmester C. P. , Fendorf M. , Wille L. T. , Gronsky R. 
Published: March 2011

ABSTRACTHigh resolution transmission electron microscopy (HRTEM) is used to investigate the transformation mechanism responsible for the occurrence of the many stable layered phases in the pseudo-binary Y2Ba4Cu6+xO14+x system. In particular, HRTEM results are compared with microstructural configurations generated by an earlier theoretical study which modeled this transformation by means of an intercalation mechanism. HRTEM images of partially transformed Y-Ba-Cu-O reveal that the predominant structural change is limited to the CuO planes. The location of the transformation front, revealed in the micrographs by the presence of these partial dislocations, suggests that the transformation is nucleated at grain boundaries and internal surfaces within the material. The observation of local CuO layer ordering along the [001] direction is taken as evidence for the presence of longer range interactions. A two-dimensional approximation to the bulk Monte Carlo simulation incorporating long range screened Coulomb [001] interactions is used to investigate the possibility and nature of local, transient stage orderings.
Misfit Dislocation Nucleation Sites and Metastability Enhancement of Selective Si1−xGex/Si Grown by Rapid Thermal Chemical Vapor Deposition
Authors: Liu C. W. , Sturm J. C. , Schwartz P. V. , Fitzgerald E. A. 
Published: March 2011

ABSTRACTA quantitative model of the effect of the selective growth on dislocation density has been developed and compared to experiments. It is concluded that the dominant dislocation nucleation source in the selective areas occurs at the specific heterogeneous sites at edges of the selective areas. This edge nucleation can be controlled by adjusting the orientation of the sidewalls.
Growth of Interfacial Phases: Effects of External and Internal Stresses
Authors: Albert D. E. , Yavari A. R. 
Published: March 2011

ABSTRACTCu/Zr-type multilayers prepared by cold-rolling have been subjected to cold and hot pressing until the onset of crystallization. It is found that application of a uniaxial stress perpendicular to the plane of the layer interfaces accelerates both the growth rate of amorphous interlayers and the onset of subsequent crystallization. These effects have been attributed to stress-induced flow parallel to the interfaces that helps relax diffusion-induced internal stresses and increases interfacial reaction constants controlling crystalline layer formation at the amorphous/Zr layer interfaces.
Computer Simulation of Plastic Deformation of Small Crystals
Authors: Doyama Masao 
Published: March 2011

ABSTRACTThe deformation of body centered iron whiskers has been simulated. The iron whisker has a very sharp yield stress. Dislocations are created in a small coppe crystal. A higher stress was needed to create the first partial dislocation but less stress to create the second partial dislocation.
Application of Stress Measurement to the Study of Thermally Activated Processes in Thin-Film Materials
Authors: Von Preissig F. J. , Nix W. D. 
Published: March 2011

ABSTRACTChanges in mechanical stress occurring in unpatterned thin films on substrates at elevated temperatures can yield information about the kinetics of the controlling processes. In this study, a specialized furnace allowed stress at elevated temperatures to be measured by the optical-lever method. The furnace was designed for good temperature control, short thermal transient periods, accurate stress measurement with low scatter, and control of the gas ambient. Stress changes in phosphosilicate glass films measured during exposure to steam at 110–150°C allowed water diffusion coefficients to be calculated. Diffusivity decreased with increasing phosphorus content and with pre-annealing treatments. The effective activation energy for water sorption was about 0.43 eV. Analysis of stress changes associated with crystallization of amorphous silicon at temperatures near 600°C yielded an effective activation energy of 3.1 eV and a density change of about 1% for the transformation.
Characterization of Thin Films by Internal Friction Measurements
Authors: Bohn H. G. , Su C. M. 
Published: March 2011

ABSTRACT: Internal friction has been employed to characterize various properties of thin Al and Al-alloy films. The grain boundary relaxation peak was useda) to determine the activation energies for grain boundary diffusion in the alloy films,b) to investigate the influence of impurities on the grain boundary diffusion in Al at concentration levels as low as 300 ppm, andc) to get information about the adhesion strength between the film and the substrate.