bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlations Between the Structure, Energy and Diffusivity of Grain and Interphase Boundaries
Authors: Muschik T. , Gust W. , Predel B. , Wolf U. , Gumbsch P. , Sommer J. , Herzig C. 
Published: March 2011

ABSTRACTThe paper illustrates the benefits of a combined use of computer simulations of interfacial properties and experiments performed on macroscopic, well-defined bicrystals. The results from two studies are reported. Relative energies of inclined Cu Σ3 grain boundaries were determined by thermal grooving experiments on diffusion-bonded Cu bicrystals. A comparison with calculated energies for crystallographically identical interfaces points to the possibility of macrofaceting of inclined grain boundaries upon annealing. Grain boundary entropy effects are discussed as another possible reason for small differences between theory and experiment. The diffusion rate of Ag* radiotracer in heterophase boundaries of diffusion-bonded Ag-Cu bicrystals can qualitatively be correlated with computed structural details of crystallographically identical Ag-Cu and Ag-Ni phase boundaries. The (computed) site-to-site variation of vacancy formation enthalpy on the (110) phase boundary leads to an anisotropy of Ag* phase boundary diffusion.
Structural and Electrical Properties of ZnO Films Deposited on GaAs Substrates by RF Magnetron Sputtering
Authors: Kim Hong Koo , Mathur Michelle 
Published: March 2011

ABSTRACTSputter deposition of ZnO films on GaAs substrates has been investigated. ZnO Alms were deposited using a ZnO compound target in Ar or Ar/O2 (95/5) ambient. Deposition parameters such as RF power, substrate-target distance, and gas composition/pressure were optimized to obtain highly c-axis oriented and highly resistive films. Deposited films were characterized by X-ray diffraction, scanning electron microscopy, capacitance, resistivity, and breakdown field strength measurements. X-ray diffraction measurements show a strong (0002)-plane peak with a full-width-half-maximum of less than 1°, indicating that the ZnO films deposited on GaAs substrates are highly c-axis oriented. DC resistivities of the films were measured to be on the order of 1011 Ω-cm.
Impedance Spectroscopic Study of Zinc Oxide Varistors
Authors: Sadhu A. , Banerjee Q. , Patni M. J. , Rananohan T. R. 
Published: March 2011

ABSTRACTPolycrystalline zinc oxide containing oxides of bismuth, cobalt, manganese and antimony is found to exhibit highly non-ohmic I–V characteristic arising due to the presence of schottky barriers at the grain boundaries. Defect states present at the grain–grain boundary interfaces store excess negative charge and give rise to such potential barriers. Any improvement in the I–V characteristics therefore demands the understanding of grain boundary properties of the material. Impedance spectroscopy is found to separate grain and grain boundary contributions in a polycrystalline material and is used to determine grain boundary contributions towards the electrical behavior of the zinc oxide varistors. It also helps in identifying stored charges and defect states present and elucidates different trapping phenomena occurring at the interface behavior of zinc oxide varistors.
Substrate Surface Effects on the Properties of Sputter-Deposited and Laser-Irradiated Films.
Authors: Pedraza A. J. , Godbole M. J. , Romana L. 
Published: March 2011

ABSTRACTSapphire substrates, mechanically polished to an optical finish, were annealed for two days at either 1000°C or 1350°C. The near surface condition of as-polished and of the annealed substrates was analyzed by Rutherford backscattering/channeling (RBS-C) and by scanning electron microscopy/channeling (SEM-C), by transmission electron microscopy (TEM), and by scanning tunnelling microscopy (STM). The polished substrates were found to be RBS-amorphous up to 100 nm, and heavily damaged at larger depths. In agreement with these results, no electron channeling was obtained from polished samples. TEM, however, showed that the damaged region was crystalline, and the only defects detected were microtwins. Both RBS-C and SEM-C analyses revealed that the damage is removed when the sapphire substrates are annealed for 48 hrs. at 1350°C. The condition of the near-surface region, viz., as-polished or annealed, is found to strongly affect the morphology of the laser-irradiated copper films deposited on sapphire substrates. A correlation is found between the threshold for film evaporation and for film rupture upon laser irradiation, both being a function of the substrate condition. It is concluded that the near-surface damaged layer acts as a thermal barrier for heat transport across the substrate.
Slip Transfer Across Interphase Boundaries in Directionally Solidified β+(γ+γ') Ni-Fe-Al Alloys
Authors: Misra A. , Gibala R. 
Published: March 2011

ABSTRACTThe low ductility and toughness of β-NiAl alloys near room temperature pose major problems in their potential application as structural materials. The inability of the material to generate and move a sufficient density of dislocations at applied stresses below the fracture stress is the major cause for this inherent brittleness. A directionally solidified β+(γ+γ') composite of nominal composition Ni50Fe30Al20 (at.%) has been used to investigate the effect of interphase boundaries on the mechanical behavior of β phase. The composite exhibits 10% tensile elongation to fracture at room temperature. Observation of slip traces and dislocation substructures shows that the normally brittle β phase undergoes extensive plastic deformation afforded by slip transfer from the plastically soft (γ+γ') phase mixture across the semi-coherent β/(γ+γ') interface. The effect of the orientation relationship between the two phases and the interface strength on the transfer of slip across the interphase boundary is discussed.
Characterization of Plasticity in Bimaterial Interface Fracture by STM
Authors: Warner Clifford P. , Bonnell Dawn A. 
Published: March 2011

ABSTRACTThe Scanning Tunneling Microscope was used as a surface profilometer to image fractured interfaces of a model metal/ceramic system, Au/sapphire. By characterizing the metal side of interface fracture, features related to plastic deformation were quantified. The spatial resolution of STM allowed these measurements to be made down to the nanometer scale. Mathematical techniques were developed to characterize surface features on several size scales and to relate them to the mechanisms from which they were produced.
The Directionality of Interfacial Cracking in Bimaterials
Authors: Wang Jian-Sheng , Beltz Glenn E. 
Published: March 2011

ABSTRACTDirectionality of interfacial cracking resistance in bicrystals has been predicted by a modified Rice-Thomson model and supported by experimental results on Σ9 [110]/(221) Cu bicrystals in Wang and Anderson's recent work. With the intention of extending this work to the behavior of interfacial cracks in dissimilar materials, Rice, Suo and Wang predicted that this directionality also occurs in bimaterials. Reported here are experimental results on Cu/sapphire specimens, which again support the prediction of the theory. A crack along the interface in a Cu/saprjhire bimaterial is brittle and decohesion of the interface occurs when the crack propagates in the [114]Cu direction, whereas it is ductile and dislocation blunting operates if the crack is intended to propagate in the [114]Cu direction. This finding is significant theoretically and is of helpful in understanding interfacial cracking in composites and film spalling in packaging materials.
Germanium Concentration Profiles Across Interfaces And Close To Dislocations In Cvd Si1−xGex-on-Si Junctions.
Authors: Bruley J. , Ernst F. , Ljutovich K. 
Published: March 2011

ABSTRACTThis work concerns a microanalytical study of CVD heteroepitaxial Si1–xGex/Si junctions with x ranging from 0.05 to 0.22. We observe that rather than being chemically abrupt, the width of the interface ranges between 200nm and 2μm with a band of misfit dislocations occupying the same region. Furthermore, the average separation of the dislocations is 2 or 3 times greater than predicted by b/δ considerations. Close scrutiny at individual dislocations within the interface region reveals a local deficit of several hundred Ge atoms per nanometer of dislocation line. It is proposed that the composition profile is rapidly spread by inter-diffusion along dislocations during the deposition process.
On The Study Of Grain Boundary Segregation Using X-Ray Diffraction And Computer Simulation
Authors: Counterman C. A. , Majid I. , Bristowe P. D. , Balluffi R. W. 
Published: March 2011

ABSTRACTThe possibility of studying grain boundary segregation using X-ray diffraction is explored by performing a computer simulation of the diffraction effects expected from the segregation of solute atoms to grain boundaries in two gold alloy systems, i.e. Au-Ag and Au-Ni. Using atomistic Monte-Carlo and molecular statics methods, equilibrium boundary structures are determined and analyzed by computing the grain boundary structure factors. Various changes in both relative and absolute grain boundary structure factors are found which can be directly related to structural and compositional changes due to segregation. In addition, systematic diffraction effects are found as a function of boundary misorientation. The experimental conditions required for verifying these predictions are discussed.
Surface Wetting By A Second Phase In A Liquid Binary Alloy
Authors: J.C Joud 
Published: March 2011

ABSTRACTThe surface tension variations of a binary two phases liquid mixture are discussed using the square gradient approximation to the free energy functional. The case of a weakly undersaturated solution at a temperature below the critical point for which we calculate a divergence of the surface tension and the layer thickness is particulary emphasized. Applications of such considerations are proposed to discuss the experimental surface tension isotherm of the liquid Sn-O system we have studied using the sessile drop technic and A.E.S. analysis.
Thermodynamic Factors Governing Interfacial Chemistry And Wetting In Binary Alloy-Refractory Oxide Systems.
Authors: V. Merlin , P. Kritsalis , L. Coudurier , N. Eustathopoulos 
Published: March 2011

ABSTRACTFor a given non-reactive metal M- refractory oxide system, the influence of a metallic solute A on interfacial chemistry and wetting depends mainly on the value of εO−A the Wagner interaction parameter which quantifies the solute A-solute oxygen interactions in the liquid matrix M.For εO−A < 0 (moderate attraction between solutes A and O) additions of A in M enhance dissolution of oxide in the liquid alloy, thereby increasing the dissolved oxygen content. The O-A clusters formed are adsorbed at the metal-oxide interface leading to an increase in both wettability and adhesion energy. For εO−A ≪0 (strong A-O interactions), solute A can also form an oxide by reduction of the substrate. The more metallic in character this oxide is, the more wettable it will be by molten metal.
Elastic Properties of Steps at Interphase Boundaries
Authors: Shiflet G. J. 
Published: March 2011

ABSTRACTStresses are introduced in crystals at interphase boundaries where steps improve the registry of atoms. A model and mathematical analysis based on an approach previously taken by van der Merwe and Shiflet1–4 of the problem incorporating a coherent step are presented. Computed distributions of stresses, strains, dilatation and energy density in the form of contours and nets are given for a coherent monatomic step. It is concluded that the maximum stresses are quite large and the fields decay fairly rapidly with distance from the steps, the gradient of dilatation around steps will significantly affect diffusion kinetics of impurities and the strain energy seems too low to significantly enhance chemical processes.
Effect of an Interfacial Ti Layer on the Formation of CoSi2 on Si
Authors: Barmak K. , Clevenger L. A. , Agnello P. D. , Ganin E. , Copel M. , Dehaven P. , Falta J. , d'Hcurle F. M. , Cabrai C. 
Published: March 2011

ABSTRACTWe have investigated the effect of an interfacial Ti layer on the mechanism of CoSi2 formation. The presence of this Ti intcrlayer shifts the completion of all the cobalt suicide reactions to higher temperatures, reduces the sensitivity of these reactions to the presence of the native oxide on silicon, and greatly modifies the morphology of the CoSi2/ < 100 > Si interface. The modification of the interface morphology arises from the formation of highly < 110 > oriented or < 100 > epitaxial CoSi2 and results in greater thermal stability of the disilicide.
The Effect of Hydrogenated Amorphous Silicon on the Formation Rate Kinetics and Crystallography of Palladium Slicide Films
Authors: Manning N. R. , Chen Haydn , Abelson J. R. , Allen L. H. 
Published: March 2011

ABSTRACTSamples of crystalline (111) silicon were coated with various thicknesses of hydrogenated amorphous silicon (a-Si:H), then coated with 100 nm of palladium. These samples were then reacted to form Pd2Si in vacuum. The activation energies and reaction prefactors were determined by monitoring the film thickness using x-ray diffraction and by 4-point resistivity measurements. The crystallographic texture of the metal overlayer and suicide films were investigated before and after the reaction.
Characterization of Inconel/Carbon Multilayer Structures
Authors: Liu J. , Cheng Y. , Lund M. W. , Wang Q. , Higgs A. 
Published: March 2011

ABSTRACTDC magnetron sputtering technique is used to fabricate inconel/carbon multilayers (ML) for applications in soft x-ray optical systems. The ML films were characterized by small angle x-ray scattering (SAXS), high resolution electron microscopy (HREM) and high-angle annular darkfield (HAADF) microscopy techniques. The HREM showed that the ML films are composed of smooth layers of amorphous components. The HAADF showed strong interdiffusion between inconel and carbon. There is no indication of any pure inconel or carbon regions in the ML films.
X-Ray Study of Interfacial Interactions in Highly Milled Sn-Ge Powders
Authors: Jayanetti J.K.D.S. , Heald S. M. , Tan Z. 
Published: March 2011

ABSTRACTWe have studied possible structural changes occur ing at the Sn/Ge interface of highly milled Sn/Ge composites. EXAFS and X-ray Diffraction measurements were made on mechanically milled powders having compositions ranging from 20 to SO vol.% Sn. X-ray diffraction measurements indicate the increasing amorphization of Sn as the Sn content is decreased. EXAFS results indicate that this amorphous phase is due to the formation of an a-Sn/Ge alloy. The EXAFS from this alloy did not change significantly at the Sn melting point. X-ray diffraction measurements made at room temperature show a systematic decrease in the intensity of Sn peaks and broadening of Ge peaks with the decreasing Sn content.
Role Of Surface Defects In Metal-Ceramic Bonding
Authors: Mukhopadhyay S. M. , Chen C. S. 
Published: March 2011

ABSTRACTThe interfacial chemistry between Ni and Al2O3 has been studied during the initial stages of bonding. We have evaporated thin films of Ni on different alumina substrates (thin oxide film on metallic Al, polished and scratched sapphire crystals, surface with second phase precipitates) and have analyzed how the interface grows, in situ, using X-ray Photoelectron Spectroscopy. It was found that a certain fraction of the first monolayer of Ni which forms on the alumina surface undergoes charge transfer to form NiO. This is due to oxygen-active sites such as unattached oxygen bonds on the surface. A measure of the concentration of such sites can therefore be obtained from the submonolayer fraction of Ni that gets oxidized. It was found that a rough surface offered less oxidation sites for Ni than a smooth one whereas a surface with second phase MgAI2O4 (spinel) precipitates offered more oxidation sites. Also, there is much less oxidation on a thin film of amorphous alumina grown on metallic Al than on a polished bulk sapphire surface. The implications of these studies to further understanding of the metal-ceramic interface have been discussed.
A Study Of Domain Boundary Structures In Lead Titanate Single Crystals
Authors: Chou C. C. , Li J. , Wayman C. M. 
Published: March 2011

ABSTRACTDomain boundary structures of flux-grown poly-domain lead titanate single crystals have been studied using transmission electron microscopy. 90° and 180° domain boundaries were seen in the crystals and were systematically analyzed under various diffraction conditions. Although 90° domain boundaries are supposely δ-type boundaries in BaTiO3, our results show that displacement plays an important role at boundaries and the extreme fringe contrast (EFC) behavior of 90° boundaries is of the mixed type. In the present work, an analysis based upon the two beam dynamical theory was conducted and a rule similar to stacking-fault contrast analysis was established to predict the geometric configuration of a 180° domain boundary using EFC behavior. Examples are given and verified by tilting experiments and electron diffraction. The results are consistent and offer a convenient way to distinguish between 90° and 180° boundaries.
Stress in Thermally Annealed Parylene Films
Authors: Dabral S. , Van Etten J. , Apblett C. , Yang G. R. , Ficalora P. , McDonald J. F. 
Published: March 2011

AbstractStress generated by thermal annealing of thick parylene-n (PA-n) films (4–7 μm) has been studied. We examined the behavior of stress for as-deposited films and rapidly thermally annealed films. The annealing was done in vacuum and the stress measured after the anneal. In another experiment the stress was also studied in-situ with thermal annealing. The as-deposited films are under compressive stress of about 18 MPa. When the backside film was removed by plasma etching, the stress changed from compressive to tensile. As the films are annealed, the stress decreases and then becomes tensile, peaking at about 60 MPa. The film crystallinity and stress are correlated for PA-n films. It was observed that stress is reduced during the crystal phase transformations at around 220°C and 270°C. This property can be used to relieve stress in multilevel structures. It was also found that slower heating and cooling led to lowered stress. The stress has been compared to reported values from other sources. Stress in PA-c (chlorinated) and co-polymerized PA-n and -e (esterfied) films has also been reported.
Elastic Constants and Viscosity of Amorphous PdSi/PdSiFe Multilayers
Authors: Witvrouw Ann , Campos Pamela , Spaepen Frans 
Published: March 2011

ABSTRACTThe biaxial elastic constants and viscosity between 100 and 300 °C of amorphous PdSi/PdSiFe multilayered thin films with repeat lengths between 2.0 and 4.9 nm have been determined using substrate curvature measurements. No dependence on repeat length has been seen for either property. Linear increases of the multilayer viscosities with time are observed. An analysis of the viscous flow of multilayers shows that in the present case this regime is reached after a very short transient period.
Superplastic Flow in Ceramic Microfiber Specimens
Authors: Lappalainen R. , Raj R. 
Published: March 2011

ABSTRACTTensile superplastic deformation was studied using ceramic specimens that had a cross section of approximately 1 μm × 10–50 μm, and a length of 4 mm. These fibers were prepared by physical vapor deposition of oxides on a predefined pattern made by lithography.Experiments with Y2O3 stabilized ZrO2 fibers and spinel fibers showed two characteristic features of flow behavior: serrations and a threshold stress. The serrations were explained by a flow model based on discrete sliding events distributed in time and space throughout the polycrystal. These fluctuations in flow stress were detected in our microfiber specimens due to relatively few grains in the gage section. Experimental results of the effect of sample size, grain size and strain rate on the serration behavior are discussed in the frame of the new model.
Experimental Determination of the Strain Transfer Across a Flexible Intermediate Layer in Thin Film Structures as a Function of Flexible Layer Thickness
Authors: Schadler L. S. , Noyan I. C. 
Published: March 2011

ABSTRACTThe tensile deformation behavior of nickel/ polyimide-thin-film / copper-thin-film structures is observed using anin situx-ray stress analysis technique. The x-ray stress is measured in the nickel and the copper simultaneously. From the analysis, the stress/strain transfer from the nickel through the polyimide to the copper can be measured.The effect of polyimide thickness (in the range from no polyimide to 33μm of polyimide) on the stress/strain transfer behavior is reported here.
Three-Dimensional Finite Element Calculations of Thermal Stresses in Patterned GaAs / Si
Authors: Lingunis E. H. , Haegel N. M. , Karam N. H. 
Published: March 2011

ABSTRACTThree-dimensional elastic finite element analysis was used to investigate the stress state in patterned GaAs/Si squares with different width to thickness ratios. Quantitative results for stress relief close to free edges were obtained. Features not revealed by previous two-dimensional calculations show the necessity of the three-dimensional treatment. For large areas the calculations give an approximately uniform biaxial stress everywhere, with reduced magnitude close to free edges. This allows for straightforward interpretation of high spatial resolution luminescence spectra and precise stress measurement. Experimental results from low temperature photoluminescence show good agreement with the calculated stresses. Finally, the effects of adjacent layers of different materials on the stress in epitaxial semiconductor thin films is investigated (particularly the case of InP/GaAs/Si) and discussed in conjunction with previous results.
Stress Driven Instability in Non-Hydrostatically Stressed Crystals and its Role in the Problems of Crystalline Thin Films
Authors: Grinfeld Michael A. 
Published: March 2011

ABSTRACTIt was demonstrated in [1] that, in the absence of surface tension aflat boundary of non-hydrostatically stressed elastic solids is always unstable with respect to “mass rearrangement”. The physical mechanisms of the rearrangement can be different, for instance, a)melting-freezing or vaporization-sublimation processes at liquid-solid or vapor-solid phase boundaries, b»surface diffusion of particles along free or interfacial boundaries, b)adsorption-desorbtion of the atoms in epitaxial crystal growth, etc… We discuss the role of this instability in the problems of epitaxy and, in particular, the opportunities delivered by this instability for explanation of the recently discovered phenomena of the dislocation-free Stranski-Krastanow pattern of growth [2]. These phenomena cannot be interpreted in the framework of traditional viewpoints since, according to the classical theory, the Stranski-Krastanow pattern is a result of proliferation of the misfit dislocation appearing on the interface “crystalline film-substratum” [3].
The Elastic Moduli of Silver Thin Films Measured with a New Microtensile Tester
Authors: Ruud J. , Josell D. , Greer A. L. , Spaepen F. 
Published: March 2011

ABSTRACTA new design for a thin film microtensile tester is presented. The strain is measured directly on the free-standing thin film from the displacement of laser spots diffracted from a thin grating applied to its surface by photolithography. The diffraction grating is two-dimensional, allowing strain measurement both along and transverse to the tensile direction. In principle, both Young's modulus and Poisson's ratio of a thin film can be determined. Ag thin films with strong <111> texture were tested. The measured Young moduli agreed with those measured on bulk crystals, but the measured Poisson ratios were low, most likely due to slight transverse folding of the film that developed during the test.