bluuebunny/crossref_metadata_2025 huggingface dataset:
Impurity Distribution Profiles and Surface Disorder after Laser Induced Diffusion.
Authors: Fogarassy E. , Stuck R. , Siffert P. , Broutet F. , Desoyer J. C.
Published: March 2011

A model for laser induced diffusion is proposed, assuming the melting of Si surface under pulsed laser irradiation and the diffusion ,in liquid phase, of a thin filmof impurity deposited according to the “limited source” conditions. Depending on the thickness of the film, it results in a dopant distribution profile with a surface disordered layer induced either by segregation effects or precipitation of the dopant in excess of the solubility limit achieved by laser annealing. Experimental results, obtained for a ruby laser irradiation of thin films of different impurities of group III and V, like antimony, bismuth, gallium and indium deposited on silicon substrates are in good agreement with the model. Their effective segregation coefficients have been deduced by fitting the experimental amount of dopant precipitated in the disordered surface layer with the numerical calculations. A cellular structure is seen on surface.
Defect Control During Epitaxial Regrowth by Rapid Thermal Annealing
Authors: Baumgart H. , Celler G. K. , Lischner D. J. , Robinson McD. , Sheng T. T.
Published: March 2011

Rapid Thermal Annealing (RTA) with tungsten halogen lamps provides excellent regrowth of silicon layers damaged by ion implantation. In addition to minimizing dopant redistribution, the inherent advantage of this technique is good control of temperature gradients. The latter is instrumental in reducing the density of extended defects in the annealed samples. In contrast, solid phase laser annealing, which involves steep temperature gradients, always leaves interstitial dislocation loops and point defect clusters. We present a comparative study of crystal quality following laser processing and incoherent light annealing as well as furnace annealing of As, P and B ion implanted Si wafers.
A Detailed Examination of Time-Resolved Pulsed Raman Temeperature Measurements of Laser Annealed Silicon
Authors: Jellison G. E. , Lowndes D. H. , Wood R. F.
Published: March 2011

Raman temperature measurements during pulsed laser annealing of Si by Compaan and co-workers are critically examined. It has been shown previously that the Stokes to anti-Stokes ratio depends critically upon the optical properties of silicon as a function of temperature. These dependences, coupled with the large spatial and temporal temperature gradients normally found immediately after the high reflectivity phase, result in large variations in the calculated temperature depending upon the probe laser pulse width and the pulse-to-pulse and spatial variations in the annealing pulse energy density.
The Contribution of Beam Processing to Present and Future Integrated Circuit Technologies
Authors: Hill C
Published: March 2011

A brief history and present state of beam processing techniques and applications to silicon integrated circuit technology are given. The viability of incorporating pulse-laser controlled doping profiles into the emitter-base structure of an advanced bipolar transistor is discussed. The areas of present I.C. technology which will constrain future device development are identified, and the contribution that beam processing can make in removing these constraints is discussed. The beam processing techniques most likely to be found in future I.C. technologies are described.
Pulsed Excimer Laser (308 nm) Annealing Of Ion Implanted Silicon and Solar Cell Fabrication
Authors: Lowndes D. H. , Cleland J. W. , Christie W. H , EBY R. E , Jellison G. E. , Narayan J. , Westbrook R. D. , Wood R. F. , Nilson J. A. , Dass S. C.
Published: March 2011

A pulsed ultraviolet excimer laser (XeCl, 308 nm wavelength, 40 nsec FWHM pulse duration) has been successfully used for laser annealing of both boron- and arsenic-implanted silicon. TEM, SIMS, and sheet electrical measurements are used to characterize specimens. C-V and I-V measurements demonstrate that near-ideal p-n junctions are formed (diode perfection factor A = 1.2). Electrical activation of implanted ions by single laser pulses is essentially complete for energy densities Eℓ≥ 1.4 J/cm2 , far below the threshold for substantial surface damage ∽4.5 J/cm2. Melting model calculations are in good agreement with observed thresholds for dopant redistribution and for epitaxial regrowth. Changes in annealing behavior resulting from multiple (1,2,5) laser pulses are also reported. Finally, we demonstrate the use of scanned overlapping excimer laser pulses for fabrication of large area (2 cm2 ) solar cells with good performance characteristics. In contrast to pulsed ruby laser annealing, high open circuit voltages can be obtained without the use of substrate heating.
Processing Of Shallow (Rp<150Å) Implanted Layers With Electron Beams
Authors: Mcmillan G.B. , Shannon J.M. , Ahmed H.
Published: March 2011

The multiple-scan method of electron beam annealing has been used to activate shallow (Rp<150Å), highly doped silicon layers produced by ion implantation of arsenic at 10keV. Beam conditions have been optimised (600Wcm−2 for 100ms) to produce essentially undiffused layers, as determined by high resolution SIMS, containing high concentrations of electrically active arsenic impurities. Computer modelling of diffusion effects in such layers has been used to identify optimum beam conditions and the calculations have been compared with experimental results. Hot electron device structures, which depend on negligible diffusion and high electrical activity, have been fabricated using the multiplescan method with a peak annealing temperature of 900°C.
A Comparison of Cw Laser and Electron-Beam Recrystallization of Polysilicon in Multilayer Structures
Authors: Drowley C.I. , Hu C.
Published: March 2011

A 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

In 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

This 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

Thin-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

We 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

Pulsed 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

InP 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

Short 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

We 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

Composition 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

The 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

Pulsed 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

In 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

The 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

The 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

The 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

Significant 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

An 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

The 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

A 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

We 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

We 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.
First-Principles Geometry Optimization of Polysilane
Authors: Mintmire John W.
Published: March 2011

A first-principles approach is reviewed for calculating the total energy of chain polymers using a linear combination of atomic orbitals local-density functional approach. The geometry for the all-trans conformation of polysilane is optimized by finding the minimum energy structure using this method.
Oxygen Precipitation in Silicon: Monte Carlo and Deterministic Studies
Authors: Lavine James P. , Taras Russell J. , Hawkins Gilbert A.
Published: March 2011

Interstitial 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

Pair 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

The 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

Using 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.
Stacking-Fault Energies in Silicon, Diamond, and Silicon Carbide
Authors: Denteneer P. J. H.
Published: March 2011

Stacking faults in a perfect crystal can be seen as limiting structures of certain series of polytypes of that crystal. A parametrization of the energy of polytypes in terms of interaction constants between layers therefore allows for the calculation of stacking-fault energies. The first-principles pseudopotential-density-functional method is used to calculate total energies of a few simple polytypes of silicon and carbon. The energies of intrinsic and extrinsic stacking faults (γISF and γESF , respectively) in silicon and diamond that follow from these calculations are in much better agreement with available experimental numbers than in previous theoretical approaches. I find: γISF = 47 mJm-2 and γESF = 36 mJm-2 for Si, γISF = 300 mJm-2 and γESF = 253 mJm-2 for diamond. From recently published similar calculations for polytypes of silicon carbide one obtains a negative energy for the extrinsic stacking fault, if zincblende silicon carbide is taken as the unfaulted structure, suggesting the observed occurrence in nature of polytypism in silicon carbide.
Molecular Dynamics Studies of Silicon Solidification and Melting
Authors: Grabow Marcia H. , Gilmer George H. , Bakker Aloysius F.
Published: March 2011

The motion of the crystal-melt interface of silicon has been investigated using molecular dynamics computer simulations. Solidification and melting have been studied for the diamond cubic (111) and (100) interfaces using the Stillinger-Weber interatomic potential for silicon. These results are compared with theory, and also with experimental results.
Atomistic Simulations of Interfaces in Metals and Alloys
Authors: Chen S. P.
Published: March 2011

We have used embedded atom potentials to simulate the surfaces, thin films and grain boundaries in metals (Ni and Al) and alloys (NiAl and Ni3Al). The calculated surface relaxations and ripplings of free surfaces are in good agreement with experiments. A new interference phenomena of interlayer relaxation in thin films are observed in the simulation. The segregation behavior of B and S and their effects on the mechanical properties of Ni3Al are correctly predicted with potentials fitted to data obtained by electronic band structure calculations.
Full Potential, Total Energy Lmto Calculation of Interface Structure in Ti-C and W-C Superlattices
Authors: Price David L. , Cooper Bernard R.
Published: March 2011

We discuss calculations of the electronic and crystallographic structure at the interfaces of titanium-carbon and tungsten-carbon superlattices. Specifically, we present total energy calculations for an arrangement of atoms designed to allow direct investigation of the competition between the formation of M-C bonds and C-C bonds. We conclude that the equilibrium structure is dominated by C-C bonding and so find that the interface has a graphite-like atomic arrangement rather than a carbide-like arrangement. These total energy calculations have been performed using a recently developed self-consistent linear combination of muffin-tin orbitals electronic structure method. This is a full-potential, all-electron, variation on standard LMTO electronic structure methods and, along with careful self-consistent determination of the parameters involved, allows accurate total energy calculations of the type of low symmetry systems involved in this study.
Computer Simulations of Epitaxial Interfaces
Authors: Dregia S. A. , Wynblatt P. , Bauer C. L.
Published: March 2011

The embedded-atom method was applied in computer simulations to study epitaxial Cu/Ag interfaces in cube-on-cube orientation relationship. Coherent and semicoherent interfaces were studied with inclinations parallel to (001), (011) and (111). The coherent boundary energy depends strongly on the predicted enthalpy of mixing. The interfacial energy for semicoherent boundaries was highly anisotropic, having its largest value (549 mJ/m2) for the (011) interface and its smallest value (231 mJ/m2) for the (111) interface. The periodic elastic relaxations correspond to networks of misfit dislocations lying in the plane of the interface; the maximum displacement in the (011) interface is about one-third the atomic diameter, but only one-eighth the atomic diameter in the (111) interface.
Mechanisms of Molecular Beam Epitaxial Growth on Reconstructed Si{100}: Thermal and Energized Beams
Authors: Garrison B. J. , Miller M. T. , Brenner D.W.
Published: March 2011

Molecular dynamics simulations have been performed that examine the microscopic mechanisms of rearrangements of atoms on the Si{ 1001 surface due to deposition of gas phase atoms. For thermal energy deposition we find that the gas atoms initially attach to dangling bonds of the surface dimer atoms. The dimer ’unreconstruction’ is due to a diffusion event on the surface, thus is temperature activated. We also find that dimers may open in regions of the surface where there are several atoms not at lattice sites, thus a low temperature amorphous structure. For 5-10 eV deposition there are direct mechanisms of dimer opening that occur on the 50-100 fs timescale. For energies greater than 15-20 eV there is implantation of the silicon atoms which leads to subsurface damage.
Beyond the Embedded Atom Interatomic Potential
Authors: Savino Eduardo J. , Pasianot R.
Published: March 2011

We briefly discuss some of the advantages and limitations of using embedded atom interatomic potentials for simulating the static configuration and dynamics of lattice defects. In metals, the embedded atom potentials provide a physically more realistic approximation than simple pair interaction potentials without a significant increase in computer time needed for defect simulation studies. However, in some cases, n-body shear forces, i.e bond angle interatomic forces may be needed for fitting experimental results related to defect configuration. One such example is the elastic neutron scattering data from N interstitials in Nb [1]. Also, such bond angle forces must be included in a realistic model of atomic interactions in metals, expecially in highly anisotropic bee transition metals. Extending the concept of the embedded atom method, we propose a new form for the interatomic potential in metals which includes bond angle forces. General expressions for the elastic constants in bee and fee structures are deduced.
A Semi-Empirical Potential for Graphite
Authors: Oh D. J. , Johnson R. A.
Published: March 2011

An Embedded Atom Method Model for graphite has been derived based on a short-range Morse two-body potential and an electron density function with both radial and angular terms. This part of the model involves interaction only within a hexagonal plane, and the interaction between planes is approximated by a Buckingham potential. The model is stable with respect to fcc, bcc, and diamond structures. The effective two-body potential is very small, indicating that defect properties are dominated by the noncentral many-body interactions.
A First-Principles Calculation of the Resistivity and Thermopower in Strong-Scattering Alloys
Authors: Brown Randall H. , Allen Philip B. , Nicholson Donald M. , Butler William H.
Published: March 2011

We investigate the concentration and short-range order dependence of the zero-temperature resistivity and thermopower for substitutionally disordered alloys from a first-principles approach. The alloy disorder is simulated by calculating the electronic structure of a large supercell (typically 200–250 atoms) with periodic boundary conditions. For the strong-scattering alloys we consider, the electron mean-free path is much less than the supercell dimension, causing artificial effects of periodicity to be negligible. In spite of strong scattering, there is no evidence for localized states near EF. The resistivity and thermopower are averaged over several configurations resulting in statistical error bounds of approximately ±10%. The concentration-dependent resistivity of substitutional V1−xAlx alloys agree well with Korringa-Kohn-Rostoker coherent potential approximation (KKR CPA) calculations. This confirms the accuracy of KKR CPA theory.
Density Profiles of Semi-Dilute Polymer Solutions Near a Hard Wall: Monte Carlo Simulation
Authors: Shih Wan Y. , Shih Wei-Heng , Aksay Ilhan A.
Published: March 2011

A semi-dilute polymer solution is one in which polymers overla1p. The bulk properties of semi-dilute polymer solutions have been studied extensively and much has been known. The scaling theory has been very successful. 1,2 The predictions of the scaling theory about various physical quantities as a function of polymer concentration, c, have been confirmed experimentally. 1,3
Bubble Dynamics in Polymer Melts
Authors: Briscoe Brian J. , Chaudhary Bharat I.
Published: March 2011

A system has been developed for studying the dynamic behaviour of gas bubbles in liquid media and is currently being used to investigate the behaviour of a single nitrogen bubble in molten LDPE. It involves the formation of an initial gas-liquid interface from a capillary by direct injection of the gas into the melt, subsequent growth until an equilibrium state is reached and the application of ambient pressure ramps which result in bubble expansion or contraction. The response depends on the rate of change of the ambient pressure. Experiments have been conducted at various temperatures above the crystalline melting temperature, Tm, of LDPE in the range 120°C-150°C. The numerical data acquired are in the form of pressure and temperature values, and these data are superimposed on stored video images of the bubbles for further processing on an image analyser whereby bubble sizes and shapes are determined.

The results obtained reveal the effect of melt viscoelasticity on the dynamics of bubbles in highly viscous fluid media. Furthermore, the changes in bubble shapes with time due to buoyancy effects are also shown. Clearly, the bubble response in the melt is governed by a combination of viscous and elastic effects. However, in the absence of suitable viscous solutions to the problem, we have attributed the behaviour to a time-dependent elastic response, but only as a first order approximation.
Corrosion of Aluminum Interconnect Passivated with Polyimide or Silicon Nitride
Authors: Comizzoli R. B. , Opila R. L. , Wong Y. H.
Published: March 2011

Polyimides have been considered the most promising organic polymers for use as an inner-layer dielectric or over-metal passivation layer on ICs. These polymers have certain processing advantages over traditional inorganic dielectrics such as SiO2 or Si3N4. However, polyimide (PI) must meet the stringent standards that inorganic materials have met, including good adhesion to the substrate and resistance to diffusion of water. Failure to meet these standards may result in increased aluminum corrosion rate and consequent degraded reliability.

In this study, the corrosion rate of sputtered aluminum test patterns passivated with either PI or plasma-deposited silicon nitride (SiN) was measured at 85°C and 85% relative humidity (RH). The objectives of this work were to: (1) assess the failure rates of biased aluminum interconnection with PI or SiN passivation; (2) determine the failure mechanisms in each case; and (3), as a result, evaluate the suitability of PI passivation for high voltage ICs in non-hermetic packages. In this report, the test device fabrication and evaluation procedures are first described. Then the results are presented, including both the failure rate measurements and the failure analyses. Finally, the results are compared and discussed.
Titanium 6/4 Single Lap Shear Adhesive Performance of Polyimide Homopolymers and Poly(Siloxane Imide) Segmented Copolymers
Authors: Yoon T. H. , Arnold C. A. , McGrath J. E.
Published: March 2011

Polyimides are attractive candidates for advanced electronic and space applications due to their high performance thermal and mechanical properties. However, the typical intractability and insolubility of polyimides has been a disadvantage. Utilization of the soluble intermediate amic acid can, to some extent, circumvent this problem. However, drawbacks to this approach include the hydrolytic instability of the amic acid and the liberation of water during its subsequent thermal cyclization. Residual stress build-up at the imide-substrate interface may occur due to swelling and drying cycles caused by the loss of water and solvent. In addition, the liberation of volatiles from a polyimide adhesive or coating can lead to the creation of voids which may significantly detract from mechanical properties. Polymeric adhesives must flow in order to provide good wetting of adherend surfaces and consolidation of the bond components. Thus, fully imidized, melt and solution processable, high Tg aromatic polyimides are of great interest.
Ion Beam Modification of Silicone Rubber
Authors: Suzuki Yoshiaki , Kusakabe Masahiro , Iwaki Masaya , Suzuki Masaaki
Published: March 2011

Ion implantation in silicone rubber has been carried out in order to study its effects on structure and chemical states. H+-, He+-, C+-, N+-, N2+-, O+-, O2+-, Ne+-, Na+-, Ar+-, and K+- ion implantations were performed at an energy of 150 keV with doses ranging from 1×1013 to 1×1017 ions/cm2 at room temperature. The depth profiles of the ion implanted elements and host elements were investigated by means of XPS and SIMS. The chemical properties were studied by FT-IR-ATR and Raman spectroscopy. XPS results indicated that most of the implanted elements showed a Gaussian like distribution in the silicone polymer matrix, but implanted He+, Ne+, and Ar+ could not be detected. Results of FT-IR-ATR showed that ion implantation broke CH3 and Si-O bonds to form new radicals such as SiOH, >C=0, CH2 and SiHx and the effects varied depending on the implanted ion species. The Raman spectroscopy results showed that ion implanted silicone contained both sp3 and sp2 bonded carbon.
“Automatized” Peel Testing: Calculated Stresses and Deflections in the Film
Authors: Suhir Ephraim
Published: March 2011

Film adhesion, which is an important reliability factor in many microelectronic structures, is usually evaluated by peel testing. The loading and the peel angle in peel tests can be controlled best if these tests are “automatized”, which could be done, for instance, by applying air pressure to a film through an opening in the substrate. We consider a rectangular opening and determine, how this pressure is related to the peel (membrane) loading and peel angle for the given film material and thickness. Our study is based on von-Kármán's equations for large deflections of plates. The obtained results provide mechanical fundamentals for a rational physical design of a peel test vehicle.
Xps Study of the Interface of Polyimide on Cr and Ni.
Authors: Garilli Marco , Marletta Giovanni , Puglisi Orazio , Oliveri Carmelo , Magro Carmelo , Ferla Giuseppe
Published: March 2011

The paper presents a study of three polyimide-oxide interfaces. The Cr-oxide-PI interface seems to undergo a drastic topographical structural rearrangement. The case of the Ni surface is indicative of heavy decomposition of the Ni oxide which induces the decomposition of the polymer film. On the contrary the stabilized Ni surface behaves in a normal manner indicating that the driving force for the decomposition is the instability of the oxide.
Ftir and Xps Studies of Polyimide/Metal Interface Formation
Authors: Stewart William C. , Leu Jihperng , Jensen Klavs F.
Published: March 2011

We describe infrared and x-ray photoelectron spectroscopy studies of the interfaces formed when the PMDA/ODA polyamic acid is imidized on gold, chromium, and copper. Polyimide films ranging from 34 ° to 1328 ° are analyzed as part of these studies. The IR and XPS results indicate that the gold interacts very little with the polyimide, while copper produces significant changes in the IR and XPS spectra. At elevated cure temperatures passivated chromium also reacts with the polyimide. In structures with chromium and copper, the thermal stability of the polyimide at the interface is reduced from that of bulk polyimide. The data demonstrate that the metals interact with the polymer structure at the point where ring closure occurs to form the polyimide from polyamic acid.
Elastic Softening in Nanocrystalline Silicon
Authors: Phillpot S. R. , Wolf D. , Lutsko J. F.
Published: March 2011

It is pointed out that some of the generic physical properties of a nanocrystalline material are similar to those of a grain-boundary superlattice. The structure and elastic properties of a superlattice of twist boundaries on the (110) plane of silicon are calculated as a function of modulation wavelength using a three-body potential. All elastic moduli are found to be softened. This softening is attributed to the relatively small amount of structural disorder at the interfaces.
Mechanical Properties of Metallic Interfaces
Authors: Walley K. P. , Gellman A. J.
Published: March 2011

We have constructed an instrument designed to make measurements of interfacial mechanical properties under ultra-high vacuum conditions. The device has been configured to allow two metallic surfaces to be prepared and characterized independently within a single UHV chamber. The two can then be brought into contact to allow measurements of the frictional properties of their interface. In this manner we are able to study the frictional properties of metallic surfaces modified by the presence of mono-molecular films. The instrument is described in this paper as are the results of initial measurements performed on modified tungsten surfaces. In addition we address the question of why it is that such ultra-thin films can modify the mechanical properties of surfaces brought into contact under macroscopic loads.
Scanning Auger and Xps Studies of Fracture Surfaces of B4C Hot Pressed with Excess Carbon
Authors: DeKoven Benjamin M. , Ness Eric A. , Hawn David D.
Published: March 2011

A series of boron carbide materials was hot pressed with 0-7% excess carbon. The strength of each material was determined by four point bending, and found to decrease from about 600MPa to 300MPa as the carbon content increased from 0% to 7%. Diamond indentation yielded hardness values that decreased from 28.3 to 25.OGPa and toughness values that increased from 3.5 to 4.5 MPa√mover the same carbon range. Each sample was fractured in situ in ultrahigh vacuum (UHV) and examined by scanning Auger microanalysis (SAM) and XPS to determine both the elemental and chemical state distributions. For the samples with excess carbon, localized carbonrich regions are observed on fracture surfaces by SAM. XPS reveals a 50% enhancement of excess carbon on the fracture surface compared to the bulk for the sample with 7% excess carbon. A correlation was observed between surface carbon composition and the bulk toughness and hardness. The C(ls) XPS spectra were utilized to determine the nature of carbon in B4C on freshly fractured and Ne+bombarded surfaces. Two distinct peaks were observed in the C(ls) region. Low dose ion bombardment resulted in a single broad C(ls) peak at the midpoint of the two initial peaks. It can be inferred from this data that there are C-C-C intericosahedral linkages in B4C.