bluuebunny/crossref_metadata_2025_split huggingface dataset:
Non-Random Mixing and Fast ion Decoupling in Lithium Chloroborate Superionic Glasses: An Ion Dynamics Computer Simulation Study
Authors: Syed R. , Kieffer J. , Angell C.A. 
Published: March 2011

AbstractLi+ions are highly mobile in LiCl-Li2O·2B23glasses to the extent that the decou-pling of conductive modes of motion from the viscous modes, assessed at the glass transition temperature Tgby a relaxation time ratio, is one of the greatest known. The interpretation of the structure of this glass system and its relation to conductivity decoupling is not very advanced at this time but there seems to be a distinction drawn between the chloroborate structure and the structure of the corresponding AgCl-Ag borate and AgI-borate glasses. The latter have frequently been discussed in terms of α-AgI percolating clusters although the available thermodynamic evidence indicates chemical ordering (negative deviations from ideal mixing) as opposed to any sort of clustering (positive deviations from ideal mixing). The LiCl-Li2O-B2O3system is interesting to us because simple transferable effective pair potentials are available for all species in the system and ion dynamics computer simulations should be capable of giving useful insights into the structure, energetics, and dynamics of the system. We present diffusivity data as a function of temperature for several compositions in the LiClLi2O·2B2O3system and observe that the Li+mobility remains high below the simulated, glass transition. Surprisingly, the Cl−anion mobility also remains high, raising a question about anion transport numbers in these glasses. Computed conductivities agree with laboratory data in the liquid state but exceed laboratory data in the glassy state in the direction expected from the high fictive temperature of simulated glass. Deviations from additivity in mixing energy in this system show a weak tendency to clustering of LiCl in the structure which suggests a need for laboratory mixing enthalpy studies.
Investigations On The Water Vapor Permeability Of Cementitious Materials Ivan Odler And Hans-Peter Barthold
Authors: Odler Ivan , Barthold Hans-Peter 
Published: March 2011

AbstractThe migration of water vapor through the existing pore system was studied on a series of cementitious, hydrothermally produced and ceramic materials with open porosities ranging between 18 and 79 per cent. Regardless on the nature of the material the water vapor migration rate increased linearly with open porosity. As to the effect of pore size, the apparent diffusion coefficient was moderately greater in pores with radii above 100μm than in smaller pores. As to the effect of relative humidity the water migration rate was greatest at high humidities and exhibited a moderate minimum at about 20–40% r.h.. At equlibrium conditions the amount of water bound in the pore system of samples through which water vapor was alloved to migrate was consistently lower than in identical samples in which just water vapor adsorption took place.
A Model for the Distribution of Pore Sizes in Cement Paste
Authors: Shi D. , Brown P. W. , Kurtz S. 
Published: March 2011

AbstractThe pore size distribution in cement paste over the range of pore sizes interrogated by high pressure mercury intrusion porosimetry may be described by a mixture of two lognormal distributions. The compound distribution of pore sizes may be given as:where p(x) is the probability density function of pores of size x, f and (1−f) are the weights of sub-distributions, μ1 and μ2 are the location parameters of sub-distributions, and σ1 and σ2 are the shape parameters of sub-distributions. These two sub-distributions may represent the larger and smaller capillary pores respectively. The changes in the sub-distributions and the compound distribution as functions of curing age and water-to-cement ratio are discussed.
An Investigation Of A High Speed Shear Mixer On Selected Pastes And Mortars
Authors: Brown M. L. , Ledbetter W. B. , Jennings H. M. 
Published: March 2011

AbstractThe influence of shear mixing on selected properties of cement pastes and mortars was investigated by preparing specimens using an ordinary paddle mixer and a high speed shear mixer. The results appear to indicate that shear mixing influences the bond between paste and aggregate, particularily at low water:cement ratios. The properties of hardened cement paste did not change markedly as a result of high speed shear mixing used in this initial study.
Influence Of Curing On Surface Characteristics Of Concrete
Authors: Sadegzadeh M. , Kettle R. J. , Page C. L. 
Published: March 2011

AbstractAn experimental assessment is presented of the influence of curing regimes on the abrasion resistance of concrete. Specimens have been produced from several different mix compositions and the abrasion resistance has been measured using a rolling-wheel apparatus. To explore these relationships, microstructural features of the cement matrix components of the surface have been studied by mercury intrusion porosimetry. The results indicate the abrasion resistance of concrete is controlled by the pore structure of the surface matrix. The nature of the curing regime having significantly influenced the pore size distribution and total pore volume of the surface matrix of the concrete surface.
A Study on the Relationship between Pore Structure and Coefficient of Permeability of Soil Stabilized with Cement
Authors: Kunito Toshimitsu , Honda Atsuhiro , Mashima Miho , Hamasato Seishi 
Published: March 2011

AbstractThis study is aimed at the quantitative evaluation of the impermeability of soil-cement in relation with soil conditions, mix proportions and curing ages. Considering the permeability coefficient as the macro property and the pore size distribution as the micro property, this paper presents the relationship between the permeability coefficient and the pore size distribution of the soil-cement. From this study, a dense soilcement with dispersed fine voids is recommended to improve the impermeability of the soil-cement.
Precipitation of Oxygen and Mechanism of Stacking Fault Formation in Czochralski Silicon Bulk Crystals
Authors: Wada Kazumi , Inoue Naohisa , Osaka Jiro 
Published: March 2011

ABSTRACTThis paper describes recent progress on nucleation and growth of oxide precipitates and stacking faults in Czochralski silicon. Conclusions on the growth kinetics of oxide precipitates are drawn from the experiments and analysis of growth kinetics of two-dimensional precipitates: The experimentally obtained growth kinetics, three-quarter power law is theoretically derived and the precipitate growth is demonstrated to be diffusion-limited by oxygen interstitials. The formation mechanism of stacking faults is the Bardeen-Herring mechanism. Based on diffusional growth model, the growth kinetics of stacking faults are analyzed, assuming a coexistence of self-interstitial supersaturation and vacancy undersaturation. It is found that the growth is driven by vacancies in undersaturation. Vacancy component of self-diffusion has been determined and found to be predominant at low temperature. The possibility of growth model proposed for increase of oxide precipitate density during annealing has been excluded. Both processes, homogeneous and heterogeneous nucleation, have been taking place during annealing.
Carbon and the Kinetics of Oxygen Precipitation in Silicon
Authors: Pinizzotto R.F. , Marks S. 
Published: March 2011

ABSTRACTOxygen precipitation in Czochralski silicon has been studied as a function of anneal time, oxygen concentration and carbon concentration using FTIR. It was found that the oxygen supersaturation controls the precipitation kinetics in high oxygen content samples, whereas the carbon concentration is of prime importance in low oxygen content samples. The decrease in sustitutional carbon concentration after nucleation and its subsequent increase with extended growth anneals supports the view that carbon affects precipitate nucleation, but not precipitate growth. The measured oxygen solubility at 1000°C was found to depend on both the initial oxygen concentration and the initial carbon concentration.
Effect of Oxygen on Radiation-Enhanced Diffusion in Silicon
Authors: Borisenko V.E. 
Published: March 2011

ABSTRACTLow-energy ion bombardment has been used to enhance diffusion of phosphorus and antimony atoms in silicon. Oxygen free silicon crystals both containing phosphorus and antimony doped surface layers and original crystals were bombarded at 400–700°C with 400 eV oxygen or argon ions. Impurity and electrical carrier profiles were measured to analyse the role of oxygen in the radiationenhanced diffusion. The results obtained are explained on assuming complexes such as vacancyoxygen and vacancy-substitutional impurity to be involved in the process.
Photoluminescence Study of Thermally Treated Silicon Crystals
Authors: Weber J. , Sauer R. 
Published: March 2011

ABSTRACTCz silicon samples heated to 450 ° C or higher temperatures for several hours exhibit many sharp photoluminescence lines well below the band edge. We study the production of the lines in terms of carbon and oxygen doping and of the heating temperature and duration. First results as to a level scheme of the P (0.7672 eV) line are reported.
Oxygen Precipitation Effects in Degenerately – Doped Silicon
Authors: Rozgonyi G. A. , Jaccodine R. J. , Pearce C. W. 
Published: March 2011

ABSTRACTIn this paper we report preliminary observations of oxygen precipitation in degenerately-doped silicon using etching, optical microscopy and transmission electron microscopy. It was found that n+ material was resistant to precipitation, but p+ material precipitated readily. A multistep heat treatment starting with a low temperature step to achieve a high supersaturation ratio was sucessfully used to induce precipitation in n+ material.
Point Defect Thermodynamics of Compound Semiconductors and their Alloys
Authors: Kröger F. A. 
Published: March 2011

ABSTRACTThe physical properties of crystalline solids depend on the presence of point defects. The concentrations of these defects in turn depend on the conditions of preparation and the presence of dopants. Quantitative relations between these conditions (partial pressures of components, concentrations of dopants, temperature) and the defect concentrations is arrived at on the basis of defect chemistry. Examples of pure and doped binary compounds, alloys of binary compounds, and ternary compounds, are given. Whereas binary compounds have one composition variable, the alloy systems and the ternary compounds have two. The role of phase diagrams in preparing systems of required composition and properties is stressed.
Self-Diffusion in Compound Semiconductors
Authors: Willoughby Arthur F.W. 
Published: March 2011

ABSTRACTSelf-diffusion studies are vital in the elucidation of atomic mechanisms of diffusion; as well as in the better understanding of device fabrication processes, such as the annealing of ion-implanted layers. This review outlines first the major reasons for interest in self-diffusion in III–V and II–VI compounds. It discusses the main differences with elemental semiconductors, including the wide variety of possible defects in the compounds, the role of departures from stoichiometry, and the value of tracer and interdiffusion studies. Self-diffusion studies in III–V compounds are next reviewed, including recent measurements in GaAs, where more information on diffusion mechanisms is becoming available. Interdiffusion between different III–V compounds is also discussed in the light of self-diffusion studies. Next, recent progress on self-diffusion in certain II–VI compounds is discussed, where interdiffusion studies have also provided a significant contribution. The review concludes by suggesting areas where research is urgently needed to clarify diffusion mechanisms.
Electrical Properties of Dislocations and Boundaries in Semiconductors
Authors: Queisser Hans J. 
Published: March 2011

ABSTRACTSimple models have been suggested to predict electronic properties of lattice defects in semiconductor crystals: dislocations ought to act via the acceptor character of dangling bonds, and small-angle grain boundaries ought to consist of regular arrays of dislocations. The actual situation in most semiconductors is, however, much more complicated. The observed electrical effects of dislocations do not confirm the dangling-bond concept, they are affected by dissociation and reconstruction. There appear to be differences between straight and kinked dislocations. Dislocations owe much of their electronic behavior to clouds and precipitates of impurities; oxygen in silicon plays a significant role. This review summarizes the present status of experimental methods and results, including luminescence and capacitance spectroscopy as well as mapping and imaging techniques using electron-microscopes.
Electronic States of Grain Boundaries in Bicrystal Silicon
Authors: Shyu C. M. , Cheng L. J. , Wang K. L. 
Published: March 2011

ABSTRACTElectronic states at a 20° symmetrical(100) tilt boundary in p-type silicon were studied using deep level transient spectroscopy (DLTS) and other electrical measurements. The data can be explained with a model in which the local barrier height at the grain boundary varies on a scale much smaller than the boundary plane (∼I mm2) under study. Based on a relationship between the carrier capture cross section and energy level deduced from the experimental data, we have been able to calculate the distribution of the density of states in the energy bandgap at the boundary, which contains two groups of continuously distributed states; a major one whose density of states increases monotonically with the position of the state from the valance band, and a minor narrow one whose density of states is centered at Ev,+0.20 eV.
The Effect of Oxygen in Cosputtered (Titanium + Silicon) Films
Authors: Beyers R. , Sinclair R. 
Published: March 2011

ABSTRACTThe effect of oxygen incorporation on the growth and microstructure of TiSi2 has been investigated. Cosputtered films, with Si/Ti ratios between one and three, were deposited on (100) Si substrates and reacted at temperatures from 650° to 1050°C. Both Auger electron spectroscopy, in conjunction with sputter profiling, and Rutherford backscattering spectrometry indicate that oxygen in the as-deposited films redistributes to the silicide-silicon interface upon heating. Cross sectional transmission electron microscope images show that the oxygen is present as an amorphous oxide.
Investigations of Metal-Silicon Interfaces by Time-of-Flight Atom Probe.
Authors: Grovenor Christopher , Smith George 
Published: March 2011

ABSTRACTThe use of a Time-of-Flight Atom Probe in the analysis of silicon surfaces, and the interfaces between metals and silicon, promises to provide very accurate chemical analysis allied with structural information from Field Ion Microscopy images. This paper presents results on the analysis of silicon surfaces by this technique,showing that good spectra can be obtained without difficulty. Some preliminary experiments on the structure of such specimens after the deposition of thin layers of Pd and Ni will be described,concentrating on the analysis of the stoichiometry of the reacted layers.
The Growth of Epitaxial NiSi2 Single Crystals on Silicon by the Use of Template Layers
Authors: Tung R. T. , Gibson J. M. , Poate J. M. 
Published: March 2011

ABSTRACTA novel crystal growth technique for NiSi2 epitaxy is presented which utilizes thin silicide (<60Å) template layers to pin the subsequent growth under ultrahigh vacuum conditions. Single crystalline NiSi2 films can be grown with either type A or type B orientations on Si(111). Continuous single crystalline NiSi2 is grown on Si(100) with flat interface and uniform thickness.
Correlation of Structure and Properties of Silicon Devices
Authors: Marcus R. B. 
Published: March 2011

ABSTRACTThree types of structure-related problems in VLSI materials and the impact of these problems on device properties are discussed: substrate defects and device leakage/breakdown, metallization linewidth and device failure, and SiO2/polysilicon interface texture and device leakage/breakdown. In many cases transmission electron microscopy is the major source of information on structure.
Donage and in Situ Annealing During Ion Implantation
Authors: Sadana D. K. , Washburn J. , Byrne P. F. , Cheung N. W. 
Published: March 2011

ABSTRACTFormation of amorphous (α) layers in Si during ion implantation in the energy range 100 KeV–11MeV and temperature range liquid nitrogen (LN)-100°C has been investigated.Cross-sectional transmission electron microscopy (XTEM) shows that buried amorphous layers can be created for both room temperature (RT) and LN temperature implants, with a wider 100 percent amorphous region for the LN cooled case. The relative narrowing of the α layer during RT implantation is attributed to in situ annealing. Implantation to the same fluence at temperatures above 100°C does not produce αlayers. To further investigate in situ annealing effects, specimens already containing buried α layers were further irradiated with ion beams in the temperature range RT-400°C. It was found that isolated small α zones (< 50 Å diameter)embedded in the crystalline matrix near the two α/c interfaces dissolved into the crystal but the thickness of the 100 percent α layer was not appreciably affected by further implantation at 200°C. A model for in situ annealing during implantation is presented.
A Comparison of Ellipsometer and Rbs Analysis of Implant Damage in Silicon
Authors: Paulson W. M. , Wilson S. R. , White C. W. , Appleton B. R. 
Published: March 2011

ABSTRACTThe purpose of this study is to analyze ion implant damage profile using RBS and ellipsometry. Silicon wafers were implanted with 75As at 100, 200 or 300 keV; doses were chosen to generate constant peak impurity concentrations at each energy. The samples were then analyzed using RBS to obtain damage- depth profiles and ellipsometry to obtain Δ,ψ parameters. At light doses decreasingΔ values correspond to increased scattering yield; at higher doses ψ increases rapidly as the scattering yield approaches the random value. The higher energy implants shift the Δ-ψ curves to larger ψ values. Multilayer structures, that include lightly damaged silicon on either side of the project range as well as more damaged near the projected range, are required to model the ellipsometer parameters.
The Study of Damage Profile of Ion Implanted Layer on Si by Spectroscopic Ellipsometry
Authors: Luo Jinshen , Mc Marr P.J. , Vedam K. 
Published: March 2011

ABSTRACTWe have determined the dielectric function of silicon samples which were implanted with 100-150 KeV P, As, Si ions to doses of 2·1014-1·1016cm−2, by a rotating analyser Automated ellipsometer in the spectral range 1.77− 4.59 eV. These data have been analyzed using a simplified three layer model.The results are compared with an earlier ellipsometric investigation [2].
Si-On-Sapphire and Si Implanted with Zr Ions: Lattice Location, Solid Phase Epitaxial Regrowth, and Electrical Properties
Authors: Golecki I. , Suni I. 
Published: March 2011

ABSTRACTZr ions have been implanted at 300 keV (Rp= 1400Å) and doses of 3×1012 − 3×l015 Zr/cm2 into Si-implanted, amorphous Sip layers on (100) bulk Si and Sion- sapphire. Rutherford backscattering and channeling spectrometry was used to study the Zr distribution and lattice location during solid-phase regrowth of the Si layers. The regrowth at 500—550°C stops at 3.4хl020 Zr/cm3, and Zr exhibits interface trapping and surface segregation effects. In this temperature range, Zr is essentially non-substitutional, and inactive electrically.
Defects in Amorphous Silicon
Authors: Biegelsen D. K. 
Published: March 2011

ABSTRACTIn this paper we argue that amorphous silicon can be treated as a relaxed continuous random network. The optical and electronic properties are controlled by localized gap states which arise from characteristic features of a disordered tetrahedrally-bonded covalent network. Experimental results are reviewed which indicate that the dominant (perhaps only) electrically-active defect in hydrogenated amorphous silicon is the topologically distinct, silicon dangling bond. Finally, we suggest that the same, disorder-related characteristics might also typify the electronic properties of some macroscopic crystalline silicon defects.
Metastable Defect Configurations in Semiconductors
Authors: Benton J. L. , Levinson M. 
Published: March 2011

ABSTRACTDeep Level Transient Spectroscopy is used to examine the stability of defect configurations in Si and InP. A systematic approach has been developed to study alternate structures of metastable defects through their representative electronic states. Regulation of defect charge state prior to analysis reveals dramatic transformations in the resulting spectra. These defect states are metastable and can be controlled with thermal or electronic energy. Model studies in electron irradiated InP and Si are presented. The barriers to configurational change are determined from the reaction kinetics. The roles of electric field, minority carrier injection and charge state are explored through junction bias techniques. It is believed that the observed behaviors represent a new class of defect reactions. The systematics of detecting and studying these reactions are presented. Model defect structures are discussed.
Micromechanics and Microdynamics Via Atomistic Simulations
Authors: Landman Uzi , Luedtke W. D. , Ribarsky M. W. 
Published: March 2011

AbstractBasic understanding of the structure and dynamics of materials and their response to external perturbations requires knowledge on the microscopic level, of the underlying energetics and atomic dynamics, whose consequences we observe and measure. Coupled with the above is the everlasting quest to observe and understand natural phenomena on refined microscopic scales, which provides the impetus for the development of experimental and theoretical techniques for the interrogation of materials with refined spatial and temporal resolution. In this paper we review the development of molecular dynamics simulations for studies of the energetics and dynamical response of materials to external mechanical perturbations. Applications to investigations of solid and liquid interfacial systems under stress and to studies of the consequences of tip-substrate interactions in atomic force microscopy are demonstrated.
Tribology of Amorphous Alloys Formed with Ion Beams
Authors: Follstaedt D. M. , Knapp J. A. , Pope L. E. 
Published: March 2011

AbstractThe changes in friction and wear properties (i.e., tribology) of steels due to thin surface alloys formed by ion beams are surveyed, and considered in light of their microstructures. Amorphous alloys containing both Ti and C are found to give superior performance in comparison to alloys with N, B, C, P or Ti. All the amorphous layers reduce friction, but the duration of benefits and wear resistance at high loads vary with composition. By examining similar amorphous alloys with Ti alone or C alone, the critical roles played by each in resisting wear are demonstrated. Amorphous alloys with Ti and C appear to be quite hard.