bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation of Extrinsic Defects at the Amorphouscrystalline Interface in Ion-Implanted Silicon
Authors: Seibt M. , Imschweiler J. , Hefner H.-A. 
Published: March 2011

AbstractWe have used high-resolution electron microscopy to examine structural changes in the amorphous - crystalline interfacial region in Ge implanted silicon due to annealing at 450°C. We observe the removal of strain in the crystalline part of the interface and a strong decrease of interfacial roughness due to annealing. In addition, we observe the nucleation of interstitial type extended defects in the crystalline region beneath the interface. These grow into {113} - stacking faults during subsequent solid-phase epitaxial regrowth. By measuring the size and density distribution of these defects we estimate the concentration profile of silicon self-interstitials in the crystalline substrate of implanted silicon.
On In-Situ Study of Dislocation/Grain Boundary Interactions Using X-ray Topography and Tem
Authors: Baker Ian , Liu Fuping 
Published: March 2011

AbstractThe advantages and disadvantages of in-situ straining using both synchrotron x-ray topography and transmission electron microscopy for examining dislocation/grain boundary interactions are compared and examples given of the use of each technique. For x-ray topography, studies on ice polycrystals are discussed. Ice is well-suited for x-ray topographic studies since it has both low absorption and can be produced with a low dislocation density. Stress concentrations have been observed at grain boundaries in ice which are partially relieved by generation of 1/3<1120> dislocations. Interestingly, grain boundary generation of dislocations completely overwhelms lattice generation mechanisms. Examples of transmission electron microscope in-situ straining studies include dislocation/grain boundary interactions in L12-structured and B2-structured intermetallics. Slip transmission across grain boundaries by dislocations gliding ahead of an advancing crack is a principal feature of these studies. A significant advantage of the such studies is their inherently high resolution. However, the dislocation behavior is dominated by the inherent thinness of the specimens.
Structure-Property Relationship of Metal-Ceramic Interfaces Produced by Laser Processing
Authors: De Hosson J.Th.M. , Zhou X.B. , Burg M. Van Den 
Published: March 2011

AbstractA novel process was developed to firmly coat an aluminium alloy, A16061, with α-A12O3 by means of laser processing. In this approach a mixture of SiO2 and Al powder was used to inject in the laser melted surface of aluminium. A reaction product α-A12O3 layer of a thickness of 100 μm was created which was well bonded to the aluminium surface.Various interfaces, A1/α-A12O3, Al/mullite and α-A12O3/;mullite, were studied by conventional transmission electron microscopy (CTEM) and high resolution electron microscope (HREM). It turns out that the presence of the A1/;muilite interface may be essential to form a well bonded oxide layer and the high Si-content α-A12O3 intermediate layer may be wetted better by liquid Al.
Atomic Scale Structure and Chemistry of Interfaces by Z-Contrast Imaging and Electron Energy Loss Spectroscopy in the Stem
Authors: Mcgibbon M.M. , Browning N.D. , Chisholm M.F. , Pennycook S.J. , Ravikumar V. , Dravid V.P. 
Published: March 2011

AbstractThe macroscopic properties of many materials are controlled by the structure and chemistry at grain boundaries. A basic understanding of the structure-property relationship requires a technique which probes both composition and chemical bonding on an atomic scale. The high-resolution Z-contrast imaging technique in the scanning transmission electron microscope (STEM) forms an incoherent image in which changes in atomic structure and composition can be interpreted intuitively. This direct image allows the electron probe to be positioned over individual atomic columns for parallel detection electron energy loss spectroscopy (EELS) at a spatial resolution approaching 0.22nm. In this paper we have combined the structural information available in the Z-contrast images with the bonding information obtained from the fine structure within the EELS edges to determine the grain boundary structure in a SrTiO3 bicrystal.
The Slip Transfer Process Through Grain Boundaries in HCP Ti
Authors: Shirokoff J. , Robertson I.M. , Birnbaum H.K. 
Published: March 2011

AbstractInformation on the mechanisms of slip transfer across grain boundaries in an HCP α-Ti alloy has been obtained from deformation experiments performed In situ in the transmission electron microscope. Initially, lattice dislocations are accommodated within the grain boundary until a critical local dislocation density is reached. The boundary then responds by activating slip in the adjoining grain on the slip system experiencing the highest local resolved shear stress and producing the residual grain-boundary dislocation with the smallest Burgers vector. Slip on secondary slip systems may be initiated provided they reduce the magnitude of the Burgers vector of, or eliminate, the residual grainboundary dislocation. The selection rules used to predict the slip system activated by the grain boundary are the same as apply in ordered and disordered FCC materials.
The Interaction Between Dislocations and Lamellar Grain Boundaries in Pst γ Tiai
Authors: Rao S. , Woodward C. , Hazzledine P.M. 
Published: March 2011

AbstractIn lamellar TiAl the flat-plate geometry of the grains, the barriers to deformation across the grain boundaries and the coherency stresses all contribute to a marked anisotropy in the yield and fracture stresses of the material. Both yield and fracture occur at low stresses when the deformation is within the lamellae (soft mode) and they occur at high stresses when the deformation crosses the lamellae (hard mode). The anisotropy is enhanced by a new effect which can soften the soft mode and harden the hard mode: the geometry of the lamellar boundary produces degeneracies in the planar fault energies at the interfaces which enhance the mobilities of dislocations on these interfaces. These degeneracies modify the core structure of dislocations on or near the interfaces, consequently soft mode dislocations can dissociate widely and move more easily when their glide plane is contained in the interface. Hard mode dislocations can substantially reduce their core energies when intersecting a γ/γ interface, and subsequently become immobilized, by cross slipping on to the interface plane. This paper presents a discussion of the geometry and relative energies of the γ/γ interfaces using elements of Bollman O-lattice theory. In order to investigate the influence of the interfaces on dislocation core structure we have fit an empirical Embedded Atom Method (EAM) potential to the structural and elastic properties of bulk L10 TiAl. The mobility and core structure of the twinning dislocation at the 180° interface and the perfect, 1/2<110] screw dislocation at the 60° and 120° interfaces were calculated using molecular statics within the EAM. We have also studied the influence of one and two atomic step ledges on dislocation mobility in the 120° interface. We find in general that dislocations are more glissile on the γ/γ interfaces, as compared to bulk TiAl and that ledges are weak barriers to dislocation glide. The interfaces themselves are strong barriers to dislocation motion in the hard mode. We find that the 1/2<110] screw dislocations gliding on conjugate {111} planes are trapped at these interfaces, as a result of lower core energies for screw dislocations lying in the interface.
Misfit Dislocations at Metal/Ceramics Interfaces
Authors: Gutekunst G. , Mayer J. , RÜHle M. 
Published: March 2011

AbstractThe atomistic structure of the coherent regions of Nb/A12O3-interfaces of various substrate orientations have been determined by high-resolution electron microscopy (HREM). The substrate surfaces were parallel to (0001)A12O3, (0110)A12O3, (2110)A12O3 and (0112)A12O3. In all cases, the Al sublattice of the A12O3 substrate is continued in the first Nb layer at the interface. This principle results in the unique orientation relationship.The Burgers vectors of the misfit dislocations and the geometry of the dislocation network of all Nb/A12O3-interfaces have been determined by HREM. All Burgers vectors are lattice vectors. Thus no coherent regions with different atomistic structures are found. The Burgers vectors are of the type 1/2<111>. These Burgers vectors correspond to the Burgers vector of bulk dislocations. All Burgers vector components which do not accommodate the lattice mismatch are compensated in the networks. The network geometry is rectangular for the following interface planes: (0110)A12O3||(112)Nb (orientation 2) and (0112)A12O3||(001)Nb. If the interface is parallel to (0001)A12O3 and (111)Nb the geometry is rhombic.The core structure of misfit dislocations of orientation 2 with line direction ξ1=[110] are calculated with an atomistic model and a continuum approach. The calculated core structures are in good agreement with the experimental HREM-micrographs of misfit dislocations of orientation 2.
Computer Simulation of Creation of Dislocations in Titanium Small Crystals
Authors: Ida Junji , Doyama Masao 
Published: March 2011

AbstractEdge dislocations were created on a basal plane (0001) in a small titanium single crystal whose surfases are (0001), (0001), (1010), (1010), (1210) and (1210) by use of n-body embedded atom potentials and molecular dynamics.
Grain Boundary Precipitate Density as a Function of Time and Misorientation in an Al-5 WT% Cu Alloy
Authors: Cantrell M. A. , Shiflet G. J. 
Published: March 2011

AbstractThe variation of θ (CuAI2) precipitate density as a function of heat treatment time and grain boundary misorientation was investigated in an Al-5 wt % Cu alloy. In this study, precipitate densities have been quantitatively linked to grain boundary structure. It was found that, for a given heat treatment time, the precipitate density varied in a reproducible manner (108 to 1010 ppts/cm2) as a function of misorientation between the grains (20 to 60 degrees). Additionally, misorientation was found to be the most important factor governing the precipitate density at a given grain boundary. The grain boundary plane orientation played a secondary role in determining the precipitate density. Bollmann O-lattice modeling allows comparison of the relative effects of grain boundary plane orientation relative to the misorientation between grains.
Computer Simulation of Vacancy Segregation at Antiphase Domain Boundaries During Coarsening
Authors: Chen Long-Qing 
Published: March 2011

AbstractA computer simulation technique based on the Master Equation Method (MEM) is developed for modeling the spatial distribution of vacancies during ordering and subsequent domain coalescence and coarsening. A vacancy mechanism is assumed for the atomic diffusion and the single-site approximation is employed. It is demonstrated that vacancies strongly segregate into the antiphase domain boundaries (APBs) during coarsening, resulting in the vacancy concentration at APBs more than an order of magnitude higher than that inside the ordered domains. As the antiphase domains coarsen, the vacancy concentration at the APBs continues to increase and its spatial s segregation profile moves accompanying the APB migration. The effect of vacancy concentration on the antiphase domain coarsening kinetics is discussed.
Interface Controlled Amorphization of Crystalline Ni/Ti Multilayers
Authors: Jankowski Alan F. , Hayes Jeffrey P. , Ramsey Philip B. 
Published: March 2011

AbstractSolid-State Amorphization (SSA) of crystalline interfaces is observed in the Ni/Ti multilayer system. The amorphization reaction nucleates at location(s) of crystallographic disorder, i.e. the multilayer interfaces. Microstructural analyses reveal the sputter-deposited growth structure to be epitaxial with semi-coherent interfaces. Strain energy originating from interface lattice distortions varies as a function of the multilayer repeat spacing. Therefore, the interfacial energy effects the onset conditions for SSA. Differential thermal analysis is used to measure the critical temperature Tc, to the nucleation of the SSA, which is found to vary with the Ni/Ti multilayer pair spacing.
Evidence by Hrem of Interfacial Modification Induced by Equilibrium Segregation in GE(S) Bicrystal
Authors: Charai A. , Rouviere J.L. 
Published: March 2011

AbstractThe structure of a [001] tilt grain boundary Σ=25(710) in germanium was investigated by HREM as prepared and after sulfur segregation. The characterisation of Ge(S) system was performed using techniques such as Auger Electron Spectroscopy, Electron Energy Loss Spectroscopy and radioactive tracer analysis. Before the sulfur introduction, this grain boundary is usually sensitive to the preferential etching during the TEM sample preparation which makes the observation difficult. This effect, depending on experimental conditions, can either partially or completely disappear. The interfacial structure as prepared and after annealing under argon or under hydrogen atmosphere can be described as a stacking of several structures with different energies. After sulfur segregation no preferential etching is observed because the lowest energy structure of the as prepared grain boundary is stabilized. The tilt angle and the plane of the grain boundary remain constant.
Correlation of Electric Parameters Change and Structural Changes Induced in Silicon Systems by Pulsed Magnetic Field Treatment
Authors: Levin Mark N. , Maslovsky Vladimir M. 
Published: March 2011

AbstractThe results of comparison investigations of structural and electric parameters changes in silicon systems induced by pulsed magnetic field (MF) treatment (PMFT) are presented for the first time. The characteristics of (PMFT) that can induce considerable parameters changes of the silicon system were determined. Amplitudc of thc magnctic impulscs is 0.1-0.3 MA/m and duration of thc impulscs is 10-30 ms. The investigations were carried out by means of scanning electron microscope (SEM), X-ray diffraction analysis, C-V and DLTS spectroscopies. The PMFT induces the generation of A-centers in the near-surface region of silicon, the changes of the crystal lattice parameter and the concentration of free electrons and results in emergence of an extent structural microdefects in subsurface. The obtained experimental data testifies that PMFT is possible to increase the vacancy concentration at subsurface region of silicon.
Transition From Inclined to In-Plane 60° Misfit Dislocations in a Diffuse Interface
Authors: Ning X. J. , Pirouz P. 
Published: March 2011

AbstractDespite tremendous activity during the last few decades in the study of strain relaxation in thin films grown on substrates of a dissimilar material, there are still a number of problems which are unresolved. One of these is the nature of misfit dislocations forming at the film/substrate interface: depending on the misfit, the dislocations constituting the interfacial network have predominantly either in-plane or inclined Burgers vectors. While, the mechanisms of formation of misfit dislocations with inclined Burgers vectors are reasonably well understood, this is not the case for in-plane misfit dislocations whose formation mechanism is still controversial. In this paper, misfit dislocations generated to relax the strains caused by diffusion of boron into silicon have been investigated by plan-view and crosssectional transmission electron microscopy. The study of different stages of boron diffusion shows that, as in the classical model of Matthews, dislocation loops are initially generated at the epilayer surface. Subsequently the threading segments expand laterally and lay down a segment of misfit dislocation at the diffuse interface. The Burgers vector of the dislocation loop is inclined with respect to the interface and thus the initial misfit dislocations are not very efficient. However, as the diffusion proceeds, non-parallel dislocations interact and give rise to product segments that have parallel Burgers vectors. Based on the observations, a model is presented to elucidate the details of these interactions and the formation of more efficient misfit dislocations from the less-efficient inclined ones.
Transmission Electron Microscopy Studies of a Complex Oxide System
Authors: Chen H. , Sung C. , Wei G.C. 
Published: March 2011

AbstractA glass ceramic based on the CaO-A12O3-BaO-MgO-B2O3 system was investigated using transmission electron microscopy in order to understand interactions among multiple oxide phases. The microstructure consisted of various crystalline and amorphous phases with stacking faults and dislocation loops in some of the crystalline phases. The microstructural development and phase assemblage of the complex system appeared to be related to defect-interface interactions during heating and cooling processes.
Characteristics of Pdai Schottky Contacts to n-GaAs
Authors: Huang T.S. , Pang J.G. 
Published: March 2011

AbstractMetallurgical and electrical properties of β-phase PdAl Schottky metallizations on n-GaAs after rapid thermal annealing for 20 s in the temperature range 500-1000°C have been investigated using x-ray diffraction, transmission electron microscopy, Auger depth profiling and current-voltage measurement. The Al-rich contacts were stable up to 900°C, whereas the Pdrich contacts were less stable. The thermal stability of Pd-rich contacts decreased with increasing Pd composition, and interfacial reaction after high temperature annealing resulted in the formation of PdGa compound. The interface between Al-rich PdAI and GaAs substrate was quite sharp even after 900°C anneal. The Schottky barrier heights of Al-rich PdAl contacts increased with annealing temperature. The barrier height enhancement in the annealed Al-rich contacts can be attributed to the thin AlxGal−xAs layer formed at the interface between PdAl and GaAs.
The Development of Solid Phase Regrowth on GaAs and its applications
Authors: Wang L. C. 
Published: March 2011

AbstractA solid phase regrowth process on GaAs has been observed in Pd- and Ni- based bi-layer structures, e.g. the Si/Ni, the Ge/Pd, the In/Pd, and the Sb/Pd structures. Due to the regrowth, uniform epitaxial layers of Ge, GaAs, InxGa1-xAs, and GaSbl-xAsx on GaAs substrates by solid phase reactions can achieved. The model of this regrowth process will be presented. Based on this regrowth mechanism, a series of non-spiking planar ohmic contacts on n and p type GaAs have been developed. Low contact resistivity in the range of mid 10−7 Ω-cm2 was obtained. The ohmic contact formation mechanism of these contacts will also be discussed. All the studies suggest that the ohmic behavior is a result of the formation of an n+ or p+ surface layer via solid phase reactions. The regrowth process has also been utilized to achieve compositional disordering of GaAs/AlGaAs superlattices, and low loss AlGaAs/GaAs waveguide has been obtained.
Radionuclide Decay Effects on Waste Glass Corrosion
Authors: Wronkiewicz D. J. 
Published: March 2011

ABSTRACTThe release of glass components into solution, including radionuclides, may be influenced by the presence of radiolytically produced nitric acid, carboxylic acid, and transient water dissociation products such as ·OH and O2-. Under batch test conditions, glass corrosion has been shown to increase up to a maximum of three-to five-fold in irradiated tests relative to nonirradiated tests, while in other studies the presence of radiolytic products has actually decreased glass corrosion rates. Bicarbonate groundwaters will buffer against pH decreases and changes in corrosion rates. Under high surface area-to-solution volume (S/V) conditions, the bicarbonate buffering reservoir may be quickly overwhelmed by radiolytic acids that are concentrated in the thin films of water contacting the samples. Glass reaction rates have been shown to increase up to 10-to-15-fold due to radiation exposure under high S/V conditions.Radiation damage to solid glass materials results in bond damage and atomic displacements. This type of damage has been shown to increase the release rates of glass components up to four-fold during subsequent corrosion tests, although under actual disposal conditions, glass annealing processes may negate the solid radiation damage effects.
Waste Glass Alteration Processes, Surface Layer Evolution and Rate Limiting Steps
Authors: Clark D. E. , Schulz R. L. , Wicks G. G. , Loading A. R. 
Published: March 2011

ABSTRACTThis paper provides an overview of waste glass alteration. Emphasis is on the evolution of surface layers and factors affecting the alteration rate when glass is subjected to an aqueous environment. The extent, type and rate of alteration is determined by a variety of parameters including time, temperature, glass composition, pH, Eh, composition of leachate/geology, the presence of other engineered barriers, flow conditions and surface area/volume ratio. Models (based on kinetic and thermodynamic considerations) developed by other researchers that are consistent with the experimental observations from the laboratory and field experiments are discussed. The morphology of the surface layers as described by interpretation of secondary ion mass spectrometry (SIMS) analyses on waste glasses and the role the various layers play in the alteration process is presented as well.
In Situ Testing of Waste Glass in Clay
Authors: Van Iseghem Pierre Ph. 
Published: March 2011

ABSTRACTThe actual status of an in-situ test programme exposing different waste glass samples directly to Boom clay is reviewed. Corrosion test tubes have been retrieved after residence for 5 years at 16° C, 2 years at 90° C, and 5 years at 170° C. The corrosion is interpreted in terms of mass loss, surface analysis by SEM and profiling by EPMA and SIMS. At 16° C, glasses dissolve about 0.02 – 0.08 µm per year. At higher temperature dissolution is more than two orders of magnitude larger. A good agreement is obtained between the mass losses and the surface analyses. The advantages and limitations of the Belgian in-situ tests are compared with the conclusions of an international expert group.
The Role of Natural Glasses as Analogues in Projecting the Long-Term Alteration of High-Level Nuclear Waste Glasses: Part 1
Authors: Mazer James J. 
Published: March 2011

ABSTRACTThe common observation of glasses persisting in natural environments for long periods of time (up to tens of millions of years) provides compelling evidence that these materials can be kinetically stable in a variety of subsurface environments. This paper reviews how natural and historical synthesized glasses can be employed as natural analogues for understanding and projecting the long-term alteration of high-level nuclear waste glasses. The corrosion of basaltic glass results in many of the same alteration features found in laboratory testing of the corrosion of high-level radioactive waste glasses. Evidence has also been found indicating similarities in the rate controlling processes, such as the effects of silica concentration on corrosion in groundwater and in laboratory leachates. Naturally altered rhyolitic glasses and tektites provide additional evidence that can be used to constrain estimates of long-term waste glass alteration. When reacted under conditions where water is plentiful, the corrosion for these glasses is dominated by network hydrolysis, while the corrosion is dominated by molecular water diffusion and secondary mineral formation under conditions where water contact is intermittent or where water is relatively scarce. Synthesized glasses that have been naturally altered result in alkali-depleted alteration features that are similar to those found for natural glasses and for nuclear waste glasses. The characteristics of these alteration features appear to be dependent on the alteration conditions which affect the dominant reaction processes during weathering. In all cases, care must be taken to ensure that the information being provided by natural analogues is related to nuclear waste glass corrosion in a clear and meaningful way.