bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural and Electrical Properties of ZnO Films Deposited on GaAs Substrates by RF Magnetron Sputtering
Authors: Kim Hong Koo , Mathur Michelle
Published: March 2011

Sputter 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

Polycrystalline 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.
Study of Magnetic Properties of Cobalt Films Grown on GaAs (110) and Au (111) Substrates Using Ferromagnetic Resonance.
Authors: Hogue K. L. , Kota C. , Naik H. M.
Published: March 2011

Ferromagnetic resonance (FMR) measurements on Co films of thicknesses 10–100 Å grown on GaAs (110) and Au (111) substrates have been made as a function of dc magnetic field orientation in a plane perpendicular to the film. Experimental data were fitted by writing the energy density expression including uniaxial perpendicular anisotropy terms up to second order and bulk anisotropy terms. Co films grown on Au (111) substrates show consistently a higher uniaxial perpendicular anisotropy compared to those grown on GaAs (110) for the same thickness of Co. This is attributed to stress induced anisotropy due to a lattice mismatch between Au (111) and Co layers.
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

Sapphire 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

The 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

The 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

Directionality 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

This 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

The 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

The 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

For 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

Stresses 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

We 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

Samples 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

DC 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

We 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

The 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

Domain 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

Stress 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

The 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

Tensile 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

The 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

Three-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

It 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

A 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.
Brllouin Light Scattering on Diamond and Diamondlike Carbon Films
Authors: Jiang X.
Published: March 2011

The set of acoustic mode frequencies associated with elastic constants has been determined from Brillouin light scattering measurements on carbon films of different crystallographic phases, i.e. on chemical vapour deposited (CVD) polycrystalline diamond, polycrystalline graphite, and amorphous carbon films (a-C:H). From the measured sound velocities of the acoustic phonons Young's moduli, shear moduli, and bulk moduli of the films were calculated. On a-C:H films depth-sensing indentation tests were performed. The values of ultramicrohardness of these films are, therefore, also reported.
Practical Application of a Geometrically Nonlinear Stress-Curvature Relation
Authors: Masters Christine B. , Salamon N. J.
Published: March 2011

A recently developed geometrically nonlinear stress-curvature relation based on a minimization of the total strain energy, which predicts a bifurcation in shape as the magnitude of intrinsic film stress increases, is discussed in this paper. It is compared with the linear theories of Stoney and Brenner & Senderoff for a thin molybdenum film on silicon substrates with various thicknesses. Although the ratio of film to substrate elastic modulus is only 2, Stoney's equation generates significant error for this film/substrate system and the Brenner & Senderoff relation should be used for calculating initial film stress when plate deflections are small. When deflections exceed approximately half the substrate thickness the Brenner & Senderoff equation produces over 10% error and consequently, the nonlinear stress-deflection relation should be used to relate plate curvatures to initial film stress.
Time-Dependent Deformation in Room-Temperature Indentation Experiments using a Nanoindenter
Authors: Baker Shefford P. , Barbee Troy W. , Nix William D.
Published: March 2011

Time-dependent deformation in room-temperature indentation is a well known phenomenon which is frequently overlooked in depth-sensing indentation experiments. In this study, the time-dependent displacements which occur during depth-sensing indentation experiments using a Nanoindenter were investigated. Time-dependent displacements were found to result both from plastic deformation of the sample and experimental drift. A simple correction for experimental drift was applied in experiments on sputtered copper thin films and reasonable strain rate sensitivities were obtained. The sources of experimental drift were identified and measured. It appears to be possible to measure the rate-dependence of plastic deformation in a variety of materials using this instrument.
Stress—Strain Behaviour of thin films using a Spherical Tipped Indenter
Authors: Bell T. J. , Field J. S. , Swain M. V.
Published: March 2011

The stress—strain behaviour of metallic and polymer thin films are measured using a spherical indenter. A modification of the Hertzian analysis enables the elastic to plastic transition to be analyzed so that the variation of mean pressure versus depth can be calculated. The stress—strain behaviour is then calculated from the mean indentation strain using a relationship proposed by Tabor[l]. Observations of high precision load displacement data generated with a UMIS—2000 instrument are analyzed on the basis of the simple analysis developed. The measured values are compared with simulated data for the same materials.
The Elastic, Plastic, and Time Dependent Properties of thin Films as Determined by Ultra low Load Indentation
Authors: Lucas B. N. , Oliver W. C.
Published: March 2011

Using a highly spatially resolved mechanical properties microprobe, the elastic, plastic and time dependent mechanical properties of sapphire and a 1.9 μm amorphous alumina film on a sapphire substrate have been studied. Young's modulus, hardness, and stress-exponent data are reported. The technique for characterizing time dependent properties via indentation (hardness versus displacement rate/displacement) are directly compared to standard uniaxial compressive techniques (stress vs strain rate) for a bulk Pb-In alloy to further quantify the relationships between the two techniques.
The Generation and Optical Activity of Misfit Dislocations by Very Low Level Transition Metal Contamination of SiGe/Si.
Authors: Kightley Philip , Higgs Victor , Goodhew Peter J
Published: March 2011

An initially pseudomorphic Sio.93Geo.07 layer is forced to relax after the deposition of 0.003 monolayers of Cu contamination and a 600°C anneal. Photoluminescence shows the dislocations have similar luminescence features (D1 to D4) to dislocations generated in bulk silicon. TEM is used to study the generation of the misfit dislocations. It is shown that the half loops form at the sample surface and a mechanism that involves the action of both the metal contaminant and the surface steps is suggested to explain the geometric arrangement of the dislocation loops that are present. The sample was found to be only 22% relaxed whereas equilibrium theory predicts 92% relaxation.
High Resolution X-Ray Studies of Ga1–xInxAs Epilayers on GaAs Substrates
Authors: Shi Yushan , Sutton Mark
Published: March 2011

By using the techniques of normal Bragg scattering and glancing incidence scattering, we have measured both the out-of-plane and in-plane structures of GaixInxAs epilay-ers grown on GaAs (001) face by MOVPE. The data presented in this paper were collected from two samples: a thick epilayer of 40, 000A Ga0.84In0.16As, and a thin epilayer of 500Å Ga0.84In0.19As, which are lattice-mismatched with the substrate by about 1.14% and 1.36% respectively according to the Vegard's law. The measured average lattice constants of the thick epilayer agree with the expectation both out-of-plane and in-plane and show nearly complete structural relaxation. An uniaxial in-plane modulation in the thick epilayer has been observed. The out-of-plane and in-plane data of the thin epilayer demonstrate a tetragonal distortion of the lattice, and the Poisson's ratio is calculated to be 0.36. The averaged in-plane lattice constant is still 0.18% larger than that of the substrate, which results in a complex structure at the epitaxial interface. An in-plane misalignment along one (110) axis in the thin epilayer has been observed.
Strain Relaxation in Heteroepitaxial Ge/Si Structures by Annealing Under Ultra High Pressure
Authors: Ishiwara Hiroshi , Sato Takayoshi , Sawaoka Akira
Published: March 2011

A novel method to solve the thermal mismatch problems in a heteroepi-taxial structure is presented, in which an amorphous film deposited on a single crystalline substrate is crystallized in solid phase by annealing under ultra high pressure and both temperature and pressure are decreased proportionally. Under a specific relation between the temperature and pressure, it is expected that the effective thermal expansion coefficients, the expansion coefficients modified by elastic strain, of the film and substrate are equal and that neither defects nor strain is generated in the film during the cooling process. Theoretical consideration and experimental results for Ge films on Si(100) substrates are presented.
Effect of Deposition Conditions on Intrinsic Stress, Phase Transformation and Stress Relaxation in Tantalum Thin Films
Authors: Mutscheller A. , Clevenger L. A. , Harper J.M.E. , Cabrai C. , Barmakt K.
Published: March 2011

We demonstrate that the high temperature polymorphic tantalum phase transition from the tetragonal beta phase to the cubic alpha phase causes complete stress relaxation and a large decrease in the resistance of tantalum thin films. 100 nm beta tantalum thin films were deposited onto thermally oxidized <100> silicon wafers by dc magnetron sputtering with argon. In situ stress and resistance at temperature were measured during temperature-ramped annealing in purified He. Upon heating, films that were initially compressively stressed showed increasing compressive stress due to thermo-elastic deformation from 25 to 550°C, slight stress relief due to plastic deformation from 550 to 700°C and complete stress relief due to the beta to alpha phase transformation at approximately 700–800°C. Incomplete compressive stress relaxation was observed at high temperatures if the film was initially deposited in the alpha phase or if the beta phase did not completely transform into alpha by 800°C. This incomplete beta to alpha phase transition was most commonly observed on samples that had radio frequency substrate bias greater than -100 V. We conclude that the main stress relief mechanism for tantalum thin films is the beta to alpha phase transformation that occurs at 700 to 800°C.
Fracture Behavior of CVD Diamond
Authors: Drory M. D. , Gardinier J. F. , Pinneo J. M.
Published: March 2011

The fracture behavior of CVD diamond is examined by indentation experiments in which slow crack growth has been observed. Diamond films of 400μm thickness were prepared by plasma-enhanced CVD on a silicon substrate, subsequently removed from the substrate, and polished for indentation testing. A microhardness tester was used to produce Vickers indentations under low load. Crack length measurements over time revealed susceptibility to slow crack growth in ambient testing conditions. The stress-corrosion susceptibility coefficient, N, was measured as 9.3.
Cracking in Thin Films and Substrates
Authors: Ståhle P. , Shih C. F.
Published: March 2011

A crack terminating perpendicularly at the bimaterial interface is analyzed. Stress distributions for a broad range of elastic moduli and yield strength mismatch are discussed. These results can be used to understand the effect of mechanical properties mismatch on the competition between crack deflecting into the interface and crack penetrating into the base material. The role of microdefects near the interface is explored.
Adhesion of Thin Metal Films to Vacuum-Cleaved SiO2, Al2O3, and MgO Substrates
Authors: Simanovskis Andris , Stolyarova Sara , Varchenya Silvia
Published: March 2011

The adhesion of Au, Ag, Pb, Sn, In, Cu, Cd, Mg, Ca films to vacuum-cleaved Al2O3, MgO and SiO2 single crystals has been studied. It is shownf -4hat for botn Al2O3 and MgO the level of adhesion is slightly higher than that for SiO2 and tends to increase with chemical activity of deposited metals. As a result, the adhesion varies from the level of van der Waals forces to the level of chemical interaction.
The Origin of Stress in Co-Cr Alloy Thin Films Deposited by Magnetron Sputtering
Authors: Zhou Zhi-Feng , Fan Yu-Dian
Published: March 2011

Co-Cr alloy thin films are considered as an applicable perpendicular magnetic recording medium, and their mechanical properties such as internal stress can not be neglected. In this experiment, Co-Cr films are deposited on glass substrates by D. C planar magnetron sputtering, and the effects of film thickness, Ni-Fe underlayer as well as substrate temperature on the stress are studied respectively. The stresses are all tensile in all cases, and the stress existing at the film-substrate interface is very small. According to the above experimental results and the structure analysis of the films, the atomic peening effect produced by the rebounded working gas atoms can be negligible, and the stress is thought to originate from the film growth process but not from the inter-facial effect. Therefore, the structural defect elimination model is proposed (here the defects mainly include vacancies and grain boundaries). With this model, the origin of the tensile stress as well as the relations between the stress and the deposition conditions are explained qualitatively.
Very Thin Protective Film of Fe-Mo-B Based Hard Alloy for Curl-Free Magnetic Tape
Authors: Akiyama Setsuo , Matsushita N. , Nakagawa S. , Naoe M.
Published: March 2011

Tribological troubles and tape-curling of perpendicular magnetic recording tapes are critical for their practical use. Thin films of a wear resistant and electrically conductive Fe-Mo-B based alloy were prepared on plasma-free tape substrates by the facing targets sputtering (FTS) method for applying them as protective layers in the magnetic tapes. The films were perfectly amorphous, very flexible and almost non-magnetic. The alloy targets for these films contained molybdenum atoms at a concentration as high as 24 at%. The Mo atomic weight is higher than that of working gas atoms Ar and Kr. Accordingly, not only Ar but also Kr atoms were recoiled from the target planes and then bombarded the growing layers to cause large compressive stress in the deposited films. Therefore, these protective films must be very thin to avoid tape-curling. Protective films as thin as 100 Å could largely reduce the dynamical friction coefficients of the surfaces of magnetic tapes owing to the hardness of their ceramic phase. In addition to this merit they possessed electrical resistivity as small as 1.2×10-4 Ω·cm. owing to their metallic binder phase. Consequently they are applicable as protective layers of curl-free magnetic tapes.
Electromigration Failure and Mechanical Stress in thin Film Conductors
Authors: Lloyd J. R.
Published: March 2011

The role of mechanical stress in electromigration of thin films is reviewed and discussed. The role of stress in the driving force and the diffusivity are seen both to be important. The concept of the activation volume is discussed with regard to information available from its measurement. It is seen that void nucleation by electromigration or stress voiding is an unsolved theoretical problem.
Effects of High Temperature Process Steps on Void Size Distributions in Passivated, Narrow Aluminum Lines
Authors: Lilienfeld D. A. , Børgesen P.
Published: March 2011

Narrow Al lines were passivated at 300°C and subsequently annealed at 400°C for an hour. The passivation layer was then removed and the lines analyzed for thermal stress induced voids. Effects of the multiple high temperature process steps necessary in chip manufacturing were simulated by repeated anneals. Renewed void nucleation occurred during cool-down from each anneal, leading to a systematic increase in void density. In contrast, the maximum void size did not increase with number of anneals while it did increase with aging time for a single anneal.
Modification of The Near-Surface Region Of Al2O3 By Ion Implantation
Authors: White C. W. , Farlow G. C. , Naramoto H. , Mchargue C. J. , Appleton B. R.
Published: March 2011

Physical and structural property changes resulting from ion implantation and thermal annealing of α-A12O3 are reviewed. Emphasis is placed on damage production during implantation, damage recovery during thermal annealing, and impurity incorporation during thermal annealing. Physical and structural property changes caused by ion implantation and annealing are correlated with changes in the mechanical properties.
Mechanical and Structural Properties of Ion Implanted Yttria Stabiizeed Zirconia Ceramics
Authors: Cochran J. K. , Legg K. O. , Solnick-Legg H. F.
Published: March 2011

Single crystal yttria stabilized zirconia was implanted with 100 keV Ca+, Al+, and O2+ ions at fluences of 1015 to 6 × 1016 ions/cm2; . Blistering was observed at doses of 3 × 1016; O2;+ cm−2; and 6 × 1016; Al+ cm−2; but none was evident with Ca+. Knoop microhardness with a shallow indenter penetration depth peaked at a dose of 1016; ions/cm−2; for both Al+ and O2;+ but Ca+ produced no effect on microhardness. Vicker's microhardness with a much greater indenter penetration depth was not changed detectably by implantation but fracture toughness measurements from the same Vicker's indentations exhibited 10–23% increases at the highest O2+ doses and 20–25% increases at high Al+ doses. Annealing the highest implant doses at 1200° reduced the fracture toughness to pre-implant levels. Reflection electron diffraction showed that the surface had not been made amorphous by the 6 × 1016; Al+ dose as a well crystallized diffraction pattern was obtained.
The effect of substitutional H− Ions on the optical and Electrical Properties of Thermochemically-Reduced MgO and CaO
Authors: Summers G. P. , Chakrabarti K.
Published: March 2011

Thermochemical reduction at high temperature of MgO and CaO single crystals introduces both anion vacancies, with absorption in the ultraviolet, and substitutional H− ions, with local mode absorptions near 1000 cm−1. The source of the hydrogen is water in the starting material. H− ions strongly influence the photoluminescence and thermoluminescence of the samples and enable F center luminescence to be excited at low temperature by low energy, E<1.8 eV, radiation. The long-lived luminescence of anion vacancies in these samples is accompanied by photoconductivity and a large dark current which increases as the concentration of H− ions increases. The activation energy for release of electrons from H= ions can be calculated from the temperature dependence of the F center luminescence decay.
Plasma

Sintering

of Ceramics
Authors: Lynn Johnson D. , Sanderson Wayne B. , Kemer Eric L. , Knowlton Jennifer
Published: March 2011

Alumina rods doped with MgO have been sintered by rapid translation through three plasma devices, namely a microwave induced plasma, a hollow cathode discharge, and an RF induction coupled plasma. Rapid densification to high density and fine grain size was observed. Some similarities and significant differences existed among the different devices.
Formation and Modification of Oxide Networks by Chemical Polymerization
Authors: Yoldas Bulent E.
Published: March 2011

The properties of glass and ceramic materials are largely determined by the types and distribution of bonds in the network structure. Since conventional methods of forming these materials by melting or sintering do not allow significant variations from the equilibrium conditions, the properties of these materials are generally fixed by the chemical composition and crystalline structure. Synthesis of these materials by chemical polymerization at low temperatures, on the other hand, permits significant modifications to the ultrastructure. These structural modifications in turn modify the material properties, without compositional alterations. In this presentation, further studies of structure-modifying parameters are discussed.
Processing and Microstructural Characterization of TiB2 Liquid Phase Sintered with Ni and Ni3Al
Authors: Angelini P. , Becher P. F. , Bentley J. , Finch C. B. , Sklad P. S.
Published: March 2011

An Analytical Electron Microscopy investigation of TiB2 hot-pressed and pressureless sintered with Ni revealed the presence of Ni3B and tau intergranular phase, respectively. Convergent Beam Electron Diffraction (CBED) was used for crystal structure determination and compositions were determined by quantitative x-ray Energy Dispersive Spectroscopy (EDS) and Electron Energy Loss Spectroscopy (EELS). The phase analyses were compared with phase diagram data. An evaluation was also made of TiB2 hot pressed with Ni3Al. Quantitative EDS and EELS microanalysis indicated a Ni,Al type boride tau (Cr23C6 type) intergranular phase.
Formation Mechanism of High Dense Form Boron Nitride Under Shock Compression
Authors: Sawaoka Akira , Akashi Tamotsu
Published: March 2011

The structural changes of graphite-like boron nitride caused by multiple shock-compressions were investigated. Wurtzite type, zinc blende type, new modification and amorphous of BN induced by multiple shock-compressions were obtained. Formation mechanism of high dense form boron nitride under shock compression was discussed.
Frictional

Hot-Spots and Propellant Sensitivity
Authors: Dienes John K.
Published: March 2011

When propellant cylinders are fired at low speeds against a steel plate, detonations are often observed. Since the process is not repeatable, and shock heating is not significant, it is natural to consider the possibility of detonation caused by hot spots. Several mechanisms are compared, and it is suggested that interfacial friction of closed cracks seems to be the most likely mechanism.
Insulator Materials in High Power Lasers for Inertial Fusion: Present and Future
Authors: Krupke William F.
Published: March 2011

Dielectric insulator materials have played a critical role in the development of high peak power solid state lasers for use in inertial confinement fusion research: as laser gain media; as transparent substrates for lenses, mirrors, and polarizers; and as active optical materials in nonlinear harmonic generators and electro-optical devices. Materials have been developed which have exceptionally high resistance to damage in the presence of intense optical beams (> GW/cm2) and which possess other properties which optimize their functions in the laser systems. Fusion lasers built to date have been designed for “single shot” operation, and the dielectric insulator materials developed for use in them have had to function under only extremely low average power loading. As we look to the future, fusion laser systems will be required to operate repetitively (few Hz) and deliver high average power output (> MW) at an efficiency greater than 10 percent. Insulator materials for use in these systems must be selected and developed on the basis of their combined mechanical, thermal, and optical properties. In this presentation, I will summarize the important characteristics of currently used insulator materials, identify figures of merit for materials needed in future systems, and outline a methodology for identifying and evaluating new materials meeting the stringent performance requirements of future fusion laser systems.
Photo-Induced Optical Switching in Mica Intercalated With Silver Compounds
Authors: Kambe N. , Yamada Tomoaki
Published: March 2011

Novel photo-induced optical phenomena observed for AgX-intercalated mica compounds are presented, where X=NO3 , Cl, Br, or I. All compounds are newly synthesized and exhibit photochromism switched by alternate illumination with 0.3∼0.4 µm and 0.7∼0.8 µm light. AgNO3 -mica furthermore yields peculiar oscillatory phenomena under continuous illumination with ∼0.8 µm light. A hypothetical mechanism for these photo-induced effects is discussed on the basis of the nonlinear excitation and relaxation processes of AgX molecules sandwitched between mica layers.
Dislocation Dissociation in MgQnAl2O3 Spinels
Authors: Wendt H. , Ostyn K. M. , Carter C. B.
Published: March 2011

The structure of low-angle tilt boundaries in magnesium-aluminate spinel has been studied by transmission electron microscopy. Special low-angle boundaries have been prepared from bicrystals but also boundaries in polycrystalline spinels were studied. The dislocations were all dissociated into partials. Their dissociation widths were found to increase with deviation from stoichiometry. Observations at lattice dislocations indicate that the composition at the boundaries may be different from the nominal composition.
The Dependence of the Deformation of Mn1-δO; on the Deviation from Stoichiometry*
Authors: Routbort J. L.
Published: March 2011

The stress-strain behavior of <100> single crystals of Mn1-δQ has been measured for the first time. The experiments were performed at 1200°C varying the oxygen partial pressure PO2 from 10-12 to 10-5 atms which causes the deviation from stoichiometry δ to vary between 5×10-2 to 2 percent. The upper yield stress and the stress achieved at a zero work-hardening rate vary by a factor of 2 as a function of δ and exhibit a maximum at pO2∼10-9 atms. The present results suggest that the diffusion of oxygen interstitials control deformation for large δ while oxygen vacancies control deformation for small δ, an interpretation used to explain the deformation Co1-δQ. These results illustrate the intimate relationship between defect properties and deformation in nonstoichiometric oxides.
Threading Dislocations in InxGabxAs/GaAs System
Authors: Tamura M. , Hashimoto A. , Nakatsugawa Y.
Published: March 2011

Threading dislocation morphologies and characters, as well as their generation conditions in InxGa1−xAs films grown by molecular-beam epitaxy on GaAs (001) substrates have been examined, mainly using cross-section al transmission electron microscopy (XTEM) as a function of x and film thickness. The formation of severe threading dislocations is detected in epilayers ofx≧0.2 at a fixed film thickness of 3 μm and with film thicknesses greater than 2μmat x=0.2. Most of the observed threading dislocations are 60°- and pure-edge type dislocations along the <211> and [001] directions, respectively. The former type dislocations are mainly observed in layers of x≧0.2; the latter predominantly exist in layers of X≧O.3.