bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Comparison of Cw Laser and Electron-Beam Recrystallization of Polysilicon in Multilayer Structures
Authors: Drowley C.I. , Hu C. 
Published: March 2011

ABSTRACTA thermal model for beam-induced melting of polysilicon in polysilicon/insulator/silicon structures has been used to compare CW Ar+ laser and electron-beam melting processes. The laser melting process exhibits a decreasing recrystallization threshold power and an increasing substrate melting threshold power with increasing insulator thickness. The decrease in recrystallization threshold with increasing insulator thickness is generally smaller for electron beams because of their deep penetration. The substrate melting threshold is approximately independent of insulator thickness for e-beams since no change in the power absorption occurs on melting of the polysilicon. As a result, the process window between the onset of recrystallization and melting of the substrate is narrower for e-beams than for laser beams. Also, essentially no window will exist between the onset of melting over a seed and substrate melting under an oxide if lateral epitaxy is performed with an electron beam.
Laser-Induced Crystallization of Silicon on Bulk Amorphous Substrates: An Overview
Authors: Biegelsen D. K. , Johnson N. M. , Hawkins W. G. , Fennell L. E. , Moyer M. D. 
Published: March 2011

ABSTRACTIn this paper we review the current understanding of laser-induced silicon thin film crystal growth on bulk amorphous substrates. We propose a model for oriented nucleation and show that the silicon reflectivity jump on melting coupled with radiant heating lead naturally to this autonucleation mechanism. We then survey various techniques for control of lateral epitaxial growth and conclude with the results of some recent electrical device characterization.
Characteristics of Recrystallised Polysilicon on SiO2 Produced by Dual Electron Beam Processing
Authors: Davis J.R. , Mcmahon R.A. , Ahmed H. 
Published: March 2011

ABSTRACTThis paper describes the production of large areas of precisely oriented, defect-free, single crystal silicon films on SiO2 by dual electron beam heating of deposited polysilicon using lateral epitaxy. Defects which occur in the film far from the seeding window are characterised, and the dependence of the area of the defect-free region on the processing conditions is discussed.
Thin-Film Transistors in CO2-Laser Crystallized Silicon Films On Fused Silica
Authors: Johnson N. M. , Tuan H. C. , Moyer M. D. , Thompson M. J. , Biegelsen D. K. , Fennell L. E. , Chiang A. 
Published: March 2011

ABSTRACTThin-film transistors (TFT) have been fabricated in scanned CO2 laser-crystallized silicon films on bulk fused silica. In n-channel enhancement-mode transistors, it is demonstrated that an excessively large leakage current can be electric-field modulated with a gate electrode located beneath the silicon layer. This dual-gate configuration provides direct verification on bulk glass substrates of back-channel leakage as has recently been demonstrated for beam-crystallized silicon films on thermal oxides over silicon wafers. With the application of deep-channel ion implantation to suppress back-channel leakage, high-peformance TFTs have been fabricated in single-crystal silicon films on fused silica. The results demonstrate that scanned CO 2 laser processing of silicon films on bulk glass can provide the basis for a silicon-on-insulator technology.
Temperature Profiles Induced By Strip Heaters
Authors: Burgener M. L. , Reedy R. E. 
Published: March 2011

ABSTRACTWe present a model based on analytic solutions to the heat equation that calculates the temperature profiles induced by line shaped heat sources. The sensitivity of isotherms to various heating conditions including the effect of tailoring power profiles in both curved and straight sources is discussed. Conditions are presented that result in “dogboned” shaped isotherms. Also shown is the effect that inhomogeneities (e.g., power density fluctuations or defects in the material have on the ideal temperature profiles.
Pulsed UV Laser Irradiation of ZNS Films on SI and GAAS
Authors: Reehal H.S. , Thomas C.B. , Gallego J.M. , Hawkins G. , Edwards C.B. 
Published: March 2011

ABSTRACTPulsed XeCl (308 nm) and XeF (351 nm) laser annealing of undoped and Mn-implanted single crystal and polycrystalline ZnS films deposited upon either Si or GaAs substrates is described. Annealing energy densities in the range ~0 .6–2.5 J cm−2 have been employed, with the specimens held under an Ar environment at ~ 100–200 psig pressure. Film thicknesses in the range ~0.2–1.0 μm have been investigated, with the substrates cleaned in various ways prior to deposition. In all the cases investigated, laser annealing results in polycrystalline regrowth of the films as shown by RHEED analysis. Furthermore the RHEED patterns obtained are consistent with the presence of both the cubic and the hexagonal phases of ZnS, except for thin (~0.2 μm thick) films annealed above ~ 2 J cm−2. These show a purely cubic structure on both Si and GaAs, possibly due to regrowth from the underlying cubic substrates.
Incoherent Focused Radiation for Activation of Implanted InP
Authors: Lorenzo J.P. , Davies D.E. , Soda K.J. , Ryan T.G. , McNally P.J. 
Published: March 2011

ABSTRACTInP layers implanted with Si+ ions are successfully activated through the use of a focused incoherent energy source. High mobility values and excellent carrier concentrations, both directly comparable to values attained using conventional furnace annealing, are achieved with this technique. Under optimized anneal conditions, electrical evaluation also indicates no surface anomalies such as those encountered with pulsed laser or electron beam annealed InP.The annealing technique described here makes use of the output from two broad spectrum 1000 watt incandescent sources. Through the use of elliptical mirrors, a combined thermal image of these sources is formed as the output at a common focus. The sample is placed at this focus during the anneal cycle. Anneal time is controlled electronically and for these experiments is varied for 1 to 15 sec. Substrate temperature is measured with a low-mass thermocouple recorder readout system placed at the focus in contact with the sample. Annealing temperatures range from 750°C to 950°C. To prevent phosphorus loss and other surface anomalies, dielectric encapsulation and a solid phosphorus proximity source technique are examined. While the proximity technique has proven useful, PSG/Si02 double layered dielectric encapsulants appear to provide the most consistent results.
Laser-Generated Glassy Phases
Authors: Von Allmen Martin 
Published: March 2011

ABSTRACTShort laser pulses have recently been discovered to be powerful means for glass formation in binary alloys as well as in some pure elements Due to relevant cooling rates in excess of 1010°K/s, glass formation is achieved in binary systems over most of the phase diagram, even in systems not previously known as glass formers. We first give a review of recent progress in laser melt quenching, and then discuss the kinetic conditions of glass formation by laser irradiation.
Pulsed Laser Melting of Metallic Glasses
Authors: Jain Animesh K. , Sood D.K. , Battaglin G. , Carnera A. , Della Mea G. , Kulkarni V.N. , Mazzoldi P. , Nandedkar R.V. 
Published: March 2011

ABSTRACTWe have studied pulsed ruby laser melting of metallic glasses – Fe40Ni40P14B6 and Fe40Ni40B20. Both amorphous and crystallised samples were used, and some of them were implanted with Ru to serve as a marker species. SEM measurements on surface topography and RBS (1.8 MeV He+) depth profiling of Ru marker redistribution were used to establish melting above about 1 J/cm2. Heat flow calculations and liquid phase diffusion analysis of the Ru marker species under a moving melt front have been performed. The observed redistribution of Ru upto 2.5 J/cm2 is consistent with an effective D ∼ 5 × 10−5 cm2 s−1. The flat Ru depth profiles at higher energy densities are shown to arise from convection effects. Results on crystallised and amorphous samples are similar. Preliminary TEM measurements of quenched regions on a crystallised sample show an unexpected absence of amorphous phase.
Pulsed Ion Beam Interface Melting of Ptcr and Crta Alloys on Si Structures
Authors: Palmstrom C. J. , Fastow R. 
Published: March 2011

ABSTRACTComposition profiles of thermal and pulsed ion beam annealed PtCr/Si and CrTa/Si have been determined using Rutherford backscattering analysis. Thermal annealing resulted in layered phase separation with Pt-silicide in the PtCr/Si case, and CrSi 2 in the CrTa/Si case, forming at the Si surface. Pulsed ion beam annealing, 300–380 keV protons at energy densities ~0.75–1.6 J/cm2 , produced interface melting with no layered phase separation.
Ultra-High Speed Solidification and Crystal Growth in Transiently Molten Semiconductor Layers
Authors: Cullis A.G. 
Published: March 2011

ABSTRACTThe use of Q-switched laser melting techniques to investigate new rapid solidification phenomena is described. It has been found that Si, Ge, GaP and GaAs can give rise to orientation dependent, kinetically-controlled defect generation processes during fast recrystallization from the melt. Indeed, these materials yield amorphous phases at sufficiently high solidification rates. Ultra-fast pulsed melting permits the study of the basic thermodynamic properties of amorphous solids. It is shown that amorphous Si melts to give a normal, low viscosity, undercooled liquid and that novel explosive crystal growth processes can occur in this low temperature regime.
Nonlinear Laser Melting Of Indium Antimonide And Silicon
Authors: Hasselbeck Michael P. , Kwok H. S. 
Published: March 2011

ABSTRACTPulsed 10.6μm TEA CO2 laser light has been used to melt the semiconductors silicon and InSb. Measurements indicate that generation of free carriers necessary for melting may take place by nonlinear processes such as two-photon absorption or intraband avalanche ionization. If the semiconductor is sufficiently doped, melting may also result from linear free carrier absorption. In all cases, it appears that the molten depth exceeds several μm, which is much greater than obtained with lasers of shorter wavelength.
Development Of Foam Glass Structural Insulation Derived from Fly Ash
Authors: Hojaji H. 
Published: March 2011

ABSTRACTIn the first part of this study, fly ash has been used as a main component in developing glass compositions which are cellulated through carbonization and oxidation processes. The resulting foam glasses have highly uniform closed pore structure and negligible water permeability with densities ranging from 140 kg/m3 to >800 kg/m3. Foam glasses with open pore structure have also been produced and characterized. In the second part, mechanical and thermal properties are discussed. These include the stressing rate effect on the fracture strength in compressive and flexural loading for different densities. Variations of thermal conductivity and overall strength with density and pore size are also described.
Porosity in the Microstructure of Blended Cements Containing Fly Ash
Authors: Patel H. H. , Pratt P. L. , Parrott L. J. 
Published: March 2011

ABSTRACTThe changes in porosity of OPC and an OPC-fly ash blended cement during hydration have been studied at water/solids ratios of 0.35, 0.47 and 0.59, cured for times of up to 1 year at 25°C. The porosity was measured indirectly by methanol exchange and methanol adsorption techniques and, directly, by quantitative image analysis using backscattered electron imaging in the scanning electron microscope. Measurements of porosity and of remaining anhydrous material by image analysis showed good correlation with indirect methods. Measurement of the diffusion of methanol and of the compressive strength were made in parallel with the determination of the porosity during hydration and attempts were made to relate the properties to the microstructure. For both binders the reduction of total porosity with increased reaction was small. The major change in pore structure was the subdivision of coarse pores by gel to form finer pores. Compressive strength and diffusion properties were dominated by the relative volume of coarse pores.
Relationships Between Permeability and Microstructural Characteristics of Fly Ash Mortars
Authors: Day Robert L. , Konecny Ladislav 
Published: March 2011

ABSTRACTThe paper describes research to evaluate permeability and the microstructure of mortars containing fly ash as a partial replacement for cement. The replacement levels of cement by fly ash were 35 and 50% by volume and 50% by weight; effectiveness of mortars made with four types of fly ash at two water/cement ratios, 0.47 and 0.65, were assessed. Three types of permeability measurements were made: (a) water permeability, (b) oxygen permeability and (c) permeability to chloride ion by the 6-hour rapid permeability test. Measurements were performed at 7, 28 and 160 days age. Strength gain in the mortar mixes was also monitored. In an attempt to explain trends observed in permeability, the pore structures of oven-dried and solventexchanged specimens were examined by mercury porosimetry. Mortars manufactured with fly ash displayed superior engineering properties when compared to the control mortars. Significant correlations were found among measurements of permeability by water, oxygen and chloride ion. Relationships were also observed between permeability and some microstructural indicators, especially the volume of mercury intruded up to a pressure of 41 MPa (6000 psi).
Heat of Hydration and Characterization of Reaction Products of Adiabatically Cured Fly Ash and Slag Mixtures
Authors: Kaushal S. , Roy D. M. , Licastro P. H. 
Published: March 2011

ABSTRACTThe hydration of cementitious materials is an exothermic process which results in significant temperature increases in large masses of these materials. The thermal environment under these conditions is nearly adiabatic. The heat of hydration of cementitious aluminosilicate blend materials incorporating fly ash and granulated blast-furnace slag was calculated from the adiabatic temperature rise. Additional reaction of siliceous fly ash with alkaline solutions results in the formation of zeolitic reaction products. Studies were carried out to characterize the hydration products by X-ray diffraction and through analysis of solutions. In addition, zeolitic reaction products were prepared by reacting the pure Class F fly ash at 90°C with NaOH and different anions. This study has implications for general thermal properties of hydrating cementitious materials, and for costeffective immobilization of radioactive and chemical waste cations and anions.
Sulphur Oxidation States in Residues from a Small-Scale Circulating Fluidized Bed Combustor
Authors: Berry E. E. , Hemmings R. T. , Cornelius B. J. , Anthony E. J. 
Published: March 2011

ABSTRACTSignificant concentrations (∼6%, as CaS) of sulphides or other reduced-sulphur species in solid residues from a small-scale circulating fluidized bed (CFB) combustor have been reported in the literature. The presence of sulphides in similar quantities in residues from a utility-scale combustor would present significant difficulties with handling, disposal or utilization of the residues. This paper discusses the preliminary findings of an investigation of sulphur capture in a small-scale circulating fluidized bed combustion (CFBC) unit using a limestone bed and burning a high-S, high-Fe, Eastern Canadian coal. Data are presented on sulphur capture and chemical speciation for residue samples taken from a number of locations in the circulating bed during operation. The results are discussed in terms of probable mechanisms for the formation of sulphur compounds of reduced oxidation state in the bed and the combustion-gas cleaning system.
Accurate Tight-Binding Studies of Antiferromagnetic States in La2CuO4
Authors: Pickett W. E. , Papaconstantopoulos D. A. 
Published: March 2011

AbstractAn accurate tight-binding parametrization of the electronic structure of La2CuO4 is used to investigate the effects of spin polarization of the Cu ion on the band structure and magnetic moment in the antiferromagnetic state. It is found that when an exchange splitting on the d(x2-y2) orbitals is imposed, a gap in the spectrum is obtained, whereas no gap is found if the splitting is imposed on all of the d orbitals or even on both d(x2 -y2) and d(z2) orbitals. This result suggests large anisotropy of the exchange field on the Cu ion.
Electronic Structure vs Phase in Al3V
Authors: Xu J.-H. 
Published: March 2011

AbstractThe electronic structure of Al3V vs its two different crystal structures (DO22 and Ll2) were investigated using local density total energy approach. The calculated results of the total energy showed that in Al3V the tetragonal DO22 phase is energetically favored as compared to the cubic Ll2 phase, the total energy in the former case is about 60 mRy/F.U. lower than that in the later case. The calculated lattice constant (a=3.72 Å, c=8.20 Å) is in fairly good agreement with experiment (a=3.778 Å, c=8.326 Å),and the bulk modulus (1.3 Mbar) is comparable with the experimental Young modulus (150 GPa) for Al3Ti. Furthermore, it is interesting to note that the density of states at EF in the tetragonal DO22 phase (0.14 states/eV-F.U.) is about one order magnitude smaller than that in the Ll2 phase (2.89 states/eV-F.U.). The electronic structure of Al3V seems to be fairly satisfactory in explaining its phase stability.
Studies of Large Lithium Clusters and their Vacancies with Highly Optimized Localized Orbitals
Authors: Pederson Mark R. , Harrison Joseph G. , Klein Barry M. 
Published: March 2011

AbstractA first-principles local-density based algorithm which employs optimized Gaussian-type orbitals is used to carry out calculations on a large variety of lithium clusters consisting of one to twenty-seven atoms. Bulk moduli, bond lengths and cohesive energies for the isolated clusters are presented and the results are extrapolated so as to predict the bulk (BCC) cohesive energy as well. Vacancy formation energies and vacancy induced lattice relaxation are also presented for three BCC fragments and compared to the bulk experimental results. For our largest cluster, we obtain a vacancy formation energy of 0.36 eV which is in good agreement with the experimental result of 0.34 eV.
Meg Density Functional Calculation of Zeolite Energies
Authors: Hummel Harry H. , Gordon Roy G. 
Published: March 2011

AbstractWe have calculated the total energy of a simple zeolite structure, sodalite, Na8Cl2Si6Al6O24 using the Modified Electron Gas (MEG) technique for the static lattice and for spherical ions. Comparison with the constituent oxides and chlorides gives a ΔGf of -0.394 au. Calculated bond lengths in the aluminosilicate framework are within 4% of the values obtained from experiment, but bond angles have error up to 12%.
A Tight Binding Monte Carlo Simulation Approach to the Cohesive Energy of Amorphous Metallic Alloys
Authors: Lançon Frederic , Billard Luc , Pasturel Alain 
Published: March 2011

AbstractWe present microscopic calculations of the cohesive energy of amorphous metallic alloys. Our method is based on a tight-binding and Monte Carlo simulation approaches to calculate the equilibrium atomic structure. The same model tight-binding Hamiltonian is then used to calculate electronic structure and energy using a Bethe-Cluster approximation.
Oxygen Precipitation in Silicon: Monte Carlo and Deterministic Studies
Authors: Lavine James P. , Taras Russell J. , Hawkins Gilbert A. 
Published: March 2011

AbstractInterstitial oxygen precipitates in silicon during thermal treatment. The amount precipitated increases in an S-shaped fashion as a function of increasing initial interstitial oxygen concentration. A likely hypothesis for this behavior is that the number of nucleation sites that develop into precipitates (successful sites) varies with the initial interstitial oxygen concentration as well as with the precipitation rate at each site. In this paper, a deterministic precipitate growth model is first used to show that a fit to the present data requires the precipitate density to increase by more than a factor of 10 when the oxygen concentration goes from 24 to 40 ppma.Three-dimensional Monte Carlo calculations are then used to show how the nucleation site survival probability depends on the initial number of oxygen atoms at the site and the oxygen concentration. The program treats oxygen diffusion, growth at nucleation sites by the addition of oxygen atoms, and loss at nucleation sites by the escape of oxygen atoms.
Computer Simulation of Point Defects in Hexagonal Close Packed Metals
Authors: Savino Eduardo J. , Monti Ana M. 
Published: March 2011

AbstractPair interaction potentials have been developed by spline fitting cubic functions to reproduce perfect lattice properties. The lattice symmetry is taken as hcp with the rigid sphere c/a ratio and a cut-off distance between second and third neighbor is assumed. The lattice parameter, elastic constants and vacancy formation energy of Mg, Ti and Zr are consistently fitted by the potentials. We have calculated the lattice relaxation predicted by these potentials for the vacancy, and self interstitial in an otherwise perfect hcp lattice. The stability and dynamics of those defects are studied within the quasi-harmonic approximation. The interstitial site occupancy in hcp lattice and the vacancy and interstitial diffusion are discussed.
The Embedded Atom Method: Theory and Application
Authors: Baskes M. I. , Daw M. S. , Foiles S. M. 
Published: March 2011

AbstractThe Embedded Atom Method (EAM), a modem theory of metallic bonding, has been developed to provide a simple but accurate method of evaluating the energy and forces for an arbitrary arrangement of atoms. The relationships between the EAM and the underlying electron density theory will be discussed. Specific examples of EAM calculations of surface reconstruction for (110) fcc materials will be predicted and compared to experiment. The examples will include temperature effects in gold. The results of molecular dynamics calculations of the mechanical properties of nickel also will be presented. Topics to be discussed include dislocation mobility and dislocation emission from a stressed crack in nickel. The dislocation calculations will be related to continuum modelling.
Molecular Dynamics Study of Crack Propagation in Ni-Al
Authors: Charpenay S. , Clapp P.C. , Rifkin J.A. , Yu Z.Z. , Voter A.F. 
Published: March 2011

AbstractUsing an Embedded Atom Method calculation of the interatomic potentials and volume forces in the Ni-Al alloy system, we have examined the plastic and elastic response of an ordered bcc Ni-Al crystal with a pre-existing crack under Mode I loading at various temperatures, stresses and crystal orientation. Depending upon those conditions we found evidence of slip and dislocation generation near the crack tip concomitant with crack propagation. we also saw evidence of a brittle to ductile transition above a certain temperature which is manifested by copious slip and dislocation production. Atomic arrays up to 4000 atoms have been studied.