bluuebunny/crossref_metadata_2025_split huggingface dataset:
Accommodation of Substrate Steps in the Growth of CoSi2 on (lll)Si
Authors: Daykin A. C. , Kiely C. J. , Pond R. C. 
Published: March 2011

ABSTRACTThin films of CoSi2 have been grown on (111) substrates of Si, and studied using transmission electron microscopy. In 2nm films, steps initially on the substrate were found to be transformed into interfacial dislocations following deposition of the films. The Burgers vectors of the dislocations were consistent with ½<101>, which includes a component ½[111] perpendicular to the interface. The contrast behaviour of these dislocations exhibited characteristic effects, which are consistent with the short-range displacement field of the defects resembling that of a disclination dipole.
Grain Boundary Structure Control for Intergranular Stress-Corrosion Resistance
Authors: Palumbo G. , King P. J. , Lichtenberger P. C. , Aust K. T. , Erb U. 
Published: March 2011

ABSTRACTA geometric model for intergranular stress corrosion cracking (IGSCC) is presented and used to evaluate the influence of grain boundary structure on the IGSCC resistance of polycrystalline materials. Preliminary observations regarding the structure of intergranular fracture paths in Alloy 600 C-ring specimens exposed to high temperature caustic media are noted to be consistent with the general predictions of the proposed geometric model and demonstrate that significant enhancement to bulk IGSCC resistance may be achieved through material processing considerations which result in (1) moderate increases in the frequency of structurally ‘special’ grain boundaries (i.e., interfaces close to low Σ CSL's) and (2) refinement in grain size.
Study of the Defect Levels and Interface Properties of CdTe and CdS Polycrystalline Thin Films
Authors: Abou-Elfotouh F. , Ashour S. , Alkuhaimi S. A. , Zhang J. , Dunlavy D. J. , Kazmerski L. L. 
Published: March 2011

ABSTRACTThe properties (electrical and structural) and the defect levels dominating cadmium telluride (CdTe) films prepared by radio frequency (rf) planar magnetron sputtering, and electrochemical deposition have been determined and compared. The properties of the deposited CdTe film and the behavior of its interface with cadmium sulfide (CdS) depend strongly on the method of depositing the CdTe film, and on postdeposition heat treatments. These treatments determine various parameters crucial to the device performance, including the type and concentration of the dominant defects, interface states, and deep trap levels. Photoluminescence (PL) emission from p-type CdTe polycrystalline thin films and single crystals is reported at low temperatures (9–50 K) as well as at room temperature. The room temperature PL peak at 1.58 eV due to band-to-band recombination was observed for the first time in polycrystalline thin films. The peak location of the exciton emission is indicative of the structure perfection of the film, which is also related to the deviation from stoichiometry. The as-grown polycrystalline films are composed of a close-packed array of preferentially oriented (the [100], [110], and [111] axes aligned perpendicular to the substrate) single-crystal grains of a size in the range of 0.25–2.0 μm for the electrochemically deposited films (E-film) and 0.3–4.0 μm for rf sputtered material (rf-film). The resistivity of the heat treated E-film was substantially lower than that of the rf-film (ρ = 1.0–5.0 and 300–500 Ωcm). The performance of the CdS/(E-CdTe) devices is limited by deep levels, while the performance of die rf-CdTe device is affected by a high density of interface states.
Fracture Strengths of Individual Grain Boundaries in Ni3Ai Using a Miniaturized Disk Bend Test
Authors: Meyers Douglas E. , Ardell Alan J. 
Published: March 2011

ABSTRACTThe results of our initial efforts at measuring the fracture strengths of grain boundaries In Ni3Al using a miniaturized disk-bend test are presented. The samples tested were 3 mm in diameter and between 150 and 300 μm thick. An Ingot of directlonally-solidlfled, boron-free Ni3Al containing 24% Al was annealed between 1300 and 1350 °C to induce grain growth, producing many grain boundaries In excess of 1.5 mm in length. Specimens were cut from these In such a way that one long grain boundary was located near a diameter of the specimen. The relative orientations of the grains on either side of the boundary were determined from electron channeling patterns. Low-angle boundaries are so strong they do not fracture; Instead the samples deform In a completely ductile manner. High-angle boundaries always fracture, but only after considerable plastic deformation of the two grains flanking them. Fracture is Indicated by a load drop in the load vs. displacement curves. A method involving extrapolation of the elastic portion of these curves to the displacement at fracture is used to estimate the fracture stresses. This procedure yields consistent values of the fracture strengths of high-angle boundaries. The measured stresses are large (∼2 to 3 GPa), but considerably smaller than those required for the fracture of special boundaries, as predicted by computer simulations. No correlation was found between the fracture stresses or loads and the geometry of the high-angle boundaries, many of which are close to, but deviate from, coincident site lattice orientations.
An Atomistic Study of Hydrogen Effects on the Fracture of Tilt Boundaries in Nickel.
Authors: Moody N. R. , Foiles S. M. 
Published: March 2011

ABSTRACTIn this study, molecular dynamics simulations were used to fracture Σ9 tilt boundaries in nickel lattices containing a range of trap site hydrogen concentrations. These lattices were created in a previous study using Monte Carlo simulations and the Embedded Atom Method to duplicate room temperature exposure to a hydrogen environment. The molecular dynamics simulations were run at absolute zero to immobilize the hydrogen distributions for determination of trap site occupancy effects on grain boundary fracture. In all lattices, fracture began by the breaking of bonds next to polyhedral defect sites that characterize the boundary structure followed by rapid failure of the remaining bonds. The effect of hydrogen was to lower the stress for fracture from 18 GPa to a lower limiting value of 8 GPa as the trap sites along the boundary plane filled. The simulations showed that the atoms at these sites were the only atoms involved in the fracture process. Within the constraints imposed on these calculations, the results of this study showed that the ‘inherent’ effect of hydrogen in the absence of plastic deformation is to reduce the cohesive force between atoms across the boundary.
Atomic Structure of Internal Interfaces in A Ti3AI-TiAI Two-Phase Alloy
Authors: Penisson J. M. , Bonnet R. , Loubradou M. , Derder C. 
Published: March 2011

ABSTRACTTiAI/Ti3AI colonies in an as-cast Ti-40 at.%AI alloy have been studied using HREM. Their microstructures consist mainly of alternating parallel lamellae of y (TiAI, L10) and α2 (Ti3AI, DO19) phases. The γ phase is often twinned with extended boundaries {111] parallel to the adjacent Ti3AI-TiAI interphase boundaries. The detailed atomic structures of the two possible (111)-γ σ3a and (111)γ σ3b twin boundaries have been observed as well as the facetted (0001)α2//(11)γ interphase boundaries. The facetted boundaries contain transformation dislocations whose elastic displacement fields conform well to the fields computed from the Somigliana dislocation model.
Effects Of Rare-Earth On Properties Of Heat-Resistant Steels And Its Interaction With Interfaces
Authors: Jihua Xu , Guichun Han , Guorong Lu , Shuping He , Dasheng Jin 
Published: March 2011

ABSTRACTEffects of rare-earth (RE) addition on creep, workability and the scaling behavior of Cr-Si, Cr-Ni and Cr-Ni-N steels were investigated. By RE additions both the creep strength and the workability of the tested steels were increased and the spalling resistance was improved. Analysis snowed that RE atoms segregated to grain boundaries, inhibiting segregation of other harmful impurities, and enhanced the cohesive strength of grain boundaries. SEM, EDX, ICP and X-ray investigations of scales showed that although no RE oxides were formed, RE modified the constituent of the scales, promoted the formation of a dense and protective scale and enhanced the cohesion between the scale and the matrix.
Prediction of First Phase Formation at Au-METAL Interfaces Using the Effective Heat of Formation Model
Authors: Pretorius R. , Marais T. K. , Muller A. E. , Knoesen D. 
Published: March 2011

ABSTRACTThe effective heat of formation model enables heats of formation to be calculated as a function of concentration. By choosing the effective concentration at the growth interface to be that of the liquidus minimum, the model correctly predicL. first phase formation for 14 binary systems for which experimental data was found, except for the Au-Cu system which does not have a well-defined minimum on the liquidus curve.
Grain Boundary Diffusivity Measurement Through Kinetic Analysis Of Discontinuous Precipitation
Authors: Manna I. , Jha J. N. , Pabi S. K. , Gust W. 
Published: March 2011

ABSTRACTDiscontinuous precipitation involves formation of a two phase aggregate from a supersaturated solid solution behind a migrating boundary. It is established that the solute transport occurs primarily through the migrating boundary, called the reaction front. This report presents a systematic study of discontinuous precipitation in a Zn-Ag alloy and measurement of grain boundary chemical diffusivity of Ag in Zn-Ag using a suitable analytical model for the first time. The necessary kinetic parameters were determined by optical and scanning electron microscopes. The activation energy for boundary chemical diffusion of Ag in Zn-Ag has been estimated to be 65.8 kJ/mol.
Observations Of Grain Growth In Thin Films
Authors: Smith D. A. , Townsend S. J. , Nichols C. S. 
Published: March 2011

ABSTRACTGrain growth occurs during the deposition and subsequent processing of metallic films. Observation of the grain structure by scanning ion probe microscopy and grain growth by in situ transmission electron microscopy using a heating stage serves to define some characteristic grain structures and their evolution in pure metal and alloy films used for metallisation.
Morphology of Si/Tungsten-Silicide/Si Interlayers
Authors: David Theodore N. , Secco d'Aragona F. , Blackstone Scott 
Published: March 2011

ABSTRACTTungsten and tungsten-silicides are of interest for semiconductor technology because of their refractory nature, low electrical-resistivity and high electromigration-resistance. This paper presents the first formation of buried tungsten-silicide layers in silicon, by proximity adhesion. The interlayers, created by a combination of chemical vapor-deposition (CVD) and proximity-adhesion were studied using transmission electron-microscopy (TEM). The behavior of the layers in the presence and absence of an adjacent silicon-dioxide interlayer was also investigated. Buried suicide layers were successfully formed with or without the adjacent silicon-dioxide. The suicide formed continuous layers with single grains encompassing the width of the interlayer. Individual grains were globular, with cusps at grain boundaries. This caused interlayer-thicknesses to be non-uniform, with lower thickness values being present at the cusps. Occasional voids were observed at grain-boundary cusps. The voids were smaller and less frequent in the presence of an adjacent oxide-layer, due to flow of the oxide during proximity adhesion. Electron-diffraction revealed a predominance of tungsten-disilicide in the interlayers, with some free tungsten being present. Stresses in the suicide layers caused occasional glide dislocations to propagate into the silicon substrate beneath the interlayers. The dislocations propagate only ∼100 nm into the substrate and therefore should not be detrimental to use of the buried layers. Occasional precipitates were observed at the end of glide-loops. These possibly arise due to excess tungsten from the interlayer diffusing down the glide dislocation to finally precipitate out as tungsten-silicide.
Microstructure and Properties of MoSi2/Nb Interfaces with and Without Alumina Coating
Authors: Xiao L. , Abbaschian R. 
Published: March 2011

ABSTRACTThis study explores the relations between processing routes, microstructures and mechanical properties of the matrix/reinforcement interfaces in MoSi2/Nb composites. It was found that the fracture energy of the interfacial region depended on the interfacial bond strength, roughness of interface, and the nature of the interfacial compounds. The fracture energy between the oxide coating and intermetallic interfacial compounds was found to be lower than that between two intermetallics or between Nb and an intermetallic. Processing routes were found to affect the fracture energy of the interfacial region by changing interphase formation, changing microstructure of materials adjacent to the interface, or changing roughness of interface.
The Evolution of Titanium-Silicon Interfaces as Monitored by X-Ray Diffraction
Authors: Novet Thomas , McConnell John , Johnson David C. 
Published: March 2011

ABSTRACTReactions in solids occur at interfaces. Following interfacial reactions has been difficult due to the small fraction of material making up the interfaces. In this paper, variable-temperature grazing x-ray diffraction is used to probe interfacial reactions in modulated ultra-thin film layered composites. This technique permits the monitoring of solid-state reactions in their earliest stages. The initial evolution of titanium-silicon interfaces within a superlattice is discussed. Our data suggest that the classical approach of modeling diffusion via Fick's laws is insufficient to describe the initial interdiffusion or mixing reaction at an interface.
CoSi2 Formation Through Co/Ti Multilayer Reacting with Si-(100) Substrate
Authors: Hong Feng , Patnaik Bijoy , Rozgonyi George A. 
Published: March 2011

ABSTRACTIn this work, Co/Ti multilayers were deposited on Si-(100) substrates by dual source thermal evaporation. Oxygen was found to be selectively incorporated into the Ti layers during the deposition. The samples were then treated by a two step annealing process. A —6nm Co2Si + CoSi2 layer was formed at the original Ti/Si interface after a 550°C, 2hr. annealing. The Ti(O) layers acted as selective diffusion membrane for Co and Si during this interaction. The morphology of the suicide layer was dependent on the thickness of the Ti(O) barrier layer. Selective removal via wet etching of the upper layers and a 750°C annealing produced stoichiometric and uniform epitaxial cobalt disilicide with a reduced film resistivity. A very flat top surface with no sign of groving or agglomeration and a much improved interface with the Si substrates were obtained.
Variable Angle Spectroscopic Ellipsometric Characterization of Polycrystalline Silicon thin Film Multilayer Structures
Authors: Snyder Paul G. , Xiong Yi-Ming , Woollam John A. , Krosche Eric R. 
Published: March 2011

ABSTRACTVariable angle spectroscopie ellipsometry (VASE), a nondestructive optical technique, was used to characterize two different multilayer samples, each having a low-pressure chemical vapor deposited polycrystalline silicon (poly-Si) layer. Analysis of these samples by cross-sectional transmission electron microscopy (XTEM) revealed large changes in grain size, between the undoped, as-deposited, and doped, annealed poly-Si layers. Roughness at the top of the poly-Si layers was also observed by XTEM. These features, together with the other structure parameters (thickness and composition), were analyzed ellipsometrically by fitting the measured VASE spectra with appropriate multilayer models. Each composite layer (surface overlayer, interfacial layer, and poly-Si layer) was modeled as a physical mixture, using the Bruggeman effective medium approximation. The ellipsometrically determined thicknesses were in very good agreement with the corresponding results measured by XTEM. Furthermore, VASE analysis provided additional information about the relative fractions of the constituent materials in the different composite layers. Thus, it quantitatively characterized the surface and interracial properties, and also the doping and annealing effects on the microstructure of poly-Si layers.
Structural Studies Of (ZnSe/FeSe) Superlattices By Transmission Electron Microscopy
Authors: Park K. , Salamanca-Riba L. , Jonker B. T. 
Published: March 2011

ABSTRACTThe structural properties of (ZnSe/FeSe) superlattices, grown with and without a ZnSe buffer layer on (001) G a As substrates by molecular beam epitaxy, have been studied by transmission electron microscopy. High quality (ZnSe/FeSe) superlattices are obtained when grown on a ZnSe buffer layer on (001) GaAs substrates. In contrast, nominal (ZnSe/FeSe) superlattices grown directly on (001) GaAs substrates without a buffer layer showed evidence for intermixing of the layers in the superlattice indicating that the superlattice is unstable. We observed a disordered structure and an ordered structure in the resulting Zn1−xFexSe solid solution. The ordered structure corresponds to chemical ordering of Zn and Fe atoms along the < 100 > and < 110 > directions. We have studied the effect of misfit strain in the (ZnSe/FeSe) superlattices on the film quality.
Electrical Resistivity And Crystal Structure Of Nickel-Based Multilayer Thin Films
Authors: Tan M. , Haftek E. , Waknis A. , Barnard J. A. 
Published: March 2011

ABSTRACTThe electrical resistivity and crystal structure of three Ni-based periodic multilayer thin film systems (Al/Ni, Ti/Ni, and Cu/Ni) have been investigated. In each series of films the Ni layer thickness was systematically varied while the thickness of the ‘spacer’ layer (Al, Ti, or Cu) was fixed. In the Al/Ni and Ti/Ni systems films with very thin Ni layers (and consequently large volume fractions of spacer and ‘interfacial’ material) yielded very high resistivities which dropped rapidly with increasing Ni thickness. By contrast, the resistivity of Cu/Ni multilayers continuously increased with Ni layer thickness due to the decline in volume fraction of high conductivity Cu. Both the Al/Ni and Ti/Ni systems exhibit Ni(111) texture in the thicker Ni layer samples. As the Ni layer thickness decreases the Ni(111) peak loses intensity and broadens due to finer grain size and increasing disorder. Al-Ni and Ti-Ni compounds are also noted. In the Cu/Ni system, however, the sharpness of the Ni(111) peak passes through a minimum as the Ni layer thickness decreases but then increases for the thinnest Ni layer samples.
SOI Interface Structures in Selective Epitaxial Growth
Authors: Weng Zara S. , Gronsky R. , Lou J. C. , Oldham W. G. 
Published: March 2011

ABSTRACTSilicon-on-insulator structures were formed by the selective epitaxial growth (SEG) of silicon and the epitaxial lateral overgrowth (ELO) of oxide shapes using an LPCVD hot-walled reactor at 850°C. The homoepitaxial interface changed character with modifications of the gas composition during the in-situ pre-epitaxial bake at 900°C. HREM images show ellipsoid-shaped inclusions lying along the homoepitaxial interface for silicon growth conducted with no dichlorosilane (DCS) flow during the prebake in H2. SIMS analysis indicates a large oxygen, fluorine, and carbon concentration at the interface. For structures grown with a small DCS flow in addition to H2 during the prebake, the homoepitaxial structural defects and the oxygen, fluorine, and carbon peaks are removed.
Grain Growth Behaviour Of Nanocrystalline Nickel
Authors: El-Sherik A. M. , Boylan K. , Erb U. , Palumbo G. , Aust K. T. 
Published: March 2011

ABSTRACTThe thermal stability of electrodeposited nanocrystalline Ni-1.2%P and Ni-0.12%S alloys is evaluated by in-situ electron microscopy studies. Isothermal grain size versus annealing time curves at 573K and 623K show an unexpected thermal stabilization in form of a transition from rapid initial grain growth to negligible grain growth. This behaviour is discussed in terms of the various grain boundary drag mechanisms which may be operative in these alloys.
Preparation And Sintering Studies Of Nanometer-Sized Polycrystalline ZrO2
Authors: Würschum R. , Soyez G. , Schaefer H.-E. 
Published: March 2011

ABSTRACTThe present paper reports on the characterization and on sintering studies of nanometer-sized polycrystalline ZrO2 prepared by the technique of crystallite condensation, oxidation, and in-situ compaction. The annealing induced growth of crystallites as well as a transformation from the tetragonal to the monoclinic phase were observed. A rapid increase of the mass density and of the microhardness during annealing up to 1000 °C indicates attractive sintering characteristics. By means of positron lifetime spectroscopy the development of the pattern of structural free volumes during sintering was studied.
Equilibrium And Non-Equilibrium Metal-Ceramic Interfaces
Authors: Gao Y. , Merkle K. L. 
Published: March 2011

ABSTRACTMetal-ceramic interfaces in theimodynamic equilibrium (Au/ZrO2) and non-equilibrium (Au/MgO) have been studied by TEM and HREM. In the Au/ZrO2 system, ZrO2 precipitates formed by internal oxidation of a 7%Zr-Au alloy show a cubic ZrO2 phase. It appears that formation of the cubic ZrO2 is facilitated by alignment with the Au matrix. Most of the ZrO2 precipitates have a perfect cube-on-cube orientation relationship with the Au matrix. The large number of interfacial steps observed in a short-time annealing experiment indicate that the precipitates are formed by the ledge growth mechanism. The lowest interfacial energy is indicated by the dominance of closed-packed {111} Au/ZrO2 interfaces. In the Au/MgO system, composite films with small MgO smoke particles embedded in a Au matrix were prepared by a thin film technique. HREM observations show that most of the Au/MgO interfaces have a strong tendency to maintain a dense lattice structure across the interfaces irrespective of whether the interfaces are incoherent or semi-coherent. This indicates that there may be a relatively strong bond between MgO and Au.
Evaluation of the Interface Structure During Stranski-Krastanov Growth of GE(SI) on Si (001)
Authors: Albrecht M. , Strunk H. P. , Hansson P. O. , Bauser E. 
Published: March 2011

ABSTRACTThe initial stages of heteroepitaxial growth of Ge0.85 Si0.15 on Si(001) grown from Bi solution (liquid phase epitaxy) are studid by transmission electron microscopy. Stranski-Krastanov growth is observed to take place. After growth of a pseudomorphic Ge0.85 Si0.15 layer of 4 monolayer thickness, islands form and grow pseudomorphically up to a thickness of 30 nm. Then first misfit dislocations form. The formation process of these dislocations is analyzed and discussed in terms of half loop nucleation at the surface and dislocation glide. Evidence for glide on (110) planes is put forward.
The Role Of Ion Species On The Adhesion Enhancement Of ION Beam Mixed Fe/Al2O3 Systems
Authors: Pawel J. E. , Mchargue C. J. , Romana L. J. , Horton L. L. , Wert J. J. 
Published: March 2011

ABSTRACTThe role of the ion species on the adhesion enhancement of ion beam mixed Fe/Al2O3 systems has been investigated. The ion implantations were carried out after film deposition using Cr (300 keV), Fe (320 keV), or Ni (340 keV) ions. The adhesion of the films was measured by a pull test and a scratch test. While the three types of implantation result in similar ion concentration profiles (with the peak concentration at the interface) and similar damage profiles, the three species were not equally effective in improving the adhesion. The effects are proposed to be due to changes in the interfacial energy resulting from both the damage and the presence of the ion species at the interface.