bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Bombardment of High Energy Ions onto Growing Surface on Structure and Properties of Sputtered Magnetic Films
Authors: Terada N. , Naoe M.
Published: March 2011

Magnetic thin films (Co-Ta, Co-Zr and pure iron films) have been deposited by means of dual ion beam sputtering and the effect of bombardment of high energy ions onto growing surface on their structure and properties has been investigated. The bombardment of argon ions with proper kinetic energy has the effects as follows;I. suppression of growth of crystallites, II. improvement of structural ordering in micro-scale and III. improvement of structural uniformity in macro-scale. Therefore, the films deposited with the proper bombardment are composed of fine crystallites with good atomic ordering. This causes an increase of 4лMs and reduction of Hc of the films;Co-Zr:4лMs=16 kG, Hc<0.6 Oe, Co-Ta:4лMs=15 kG,Hc<0.3 Oe and iron films:4лMs=21 kG,Hc=l Oe.
Shape Memory Behaviour in Rapidly Solidified TiNi Alloys
Authors: Igharo M. , Wood J.V.
Published: March 2011

Equiatomic TiNi alloy has been rapidly solidified by melt spinning. The M3 temperature of ribbon is depressed with respect to samples made from elemental powders. This phenomenon is related to grain refinement. Some of the ribbons have been crushed and the consolidation characteristics of the resulting pre-alloyed powder is compared with that of elemental blends. Sintering activity is higher in elemental compacts as a result of the dominant effect of the a]loy formation energy in elemental blends.
Comparison of Structures of Gas Atomized and of Emulsified Highly Undercooled Ni-Sn Alloy Droplets
Authors: Yamamoto Michiharu , Wu Yanzhong , Shiohara Yuh , Flemings Merton C.
Published: March 2011

A comparison is made of microstructures of droplets of Ni-Sn alloys rapidly solidified (a) by gas atomization and (b) in a glass emulsifying medium. Cooling rate of the gas atomized particles ranged from 103 to 106K/s depending on droplet diameter (20-230μm). In the hypoeutectic alloy studied (Ni-25wt%Sn), most particles showed a dendritic structure. These same particles, melted and resolidified in a glass medium using DTA (Differential Thermal Analysis), showed undercoolings up to 280K: the structures were dendritic at low undercoolings and non-dendritic at undercoolings above about 220K. It is concluded that (1) the gas atomized particles exhibited little or no undercooling before nucleation, (2) the solidification time of the undercooled emulsified droplets is substantially less than that of gas atomized droplets, and (3) the undercooling required to achieve non-dendritic structure depends on sample size.
Improvement of Thermal Fatigue Resistance of A Wrought Nickel-Base Superalloy by Laserglaze
Authors: Qi Zhao , Yunlong Ge , Zhuangqi Hu , Ming Jiang , Changshu Shih
Published: March 2011

Laserglaze with appropriate post heat treatment has improved the thermal fatigue resistance of a wrought nickel-base superalloy. It was found that laserglaze was able to eliminate the blocky MC phase, refine grains and form a very interesting microstructure of serrated grain boundaries. Careful selection of post heat treatment markedly increased the strength in the laser irradiated region. The initiation and propagation of thermal fatigue cracks were suppressed by this novel microstructure.
Electronic Structure and Glass Formability in Metallic Glasses
Authors: Hasegawa R. , Tanaka K.
Published: March 2011

Recent developments in theory and experiment seem to enable us to relate the electronic structure to the formability of glassy states in transition metal-metalloid base alloys. Especially stressed is the role of the antibonding states in the glass formation.
High Resolution Transmission Electron Microscope Study of Amorphous and Partially Crystalline Fe7 8B1 3Si9Alloy
Authors: Bhatti A.R. , Barry J.C. , Cantor B
Published: March 2011

Amorphous and partially crystalline Fe7 8B1 3Si9alloys have been examined by high resolution transmission electron microscopy at 200kV. In lattice imaging mode, the as-quenched alloy shows small regions, with a mean size of - 20Å, consisting of well defined patterns of fringes. Three different types of crystals can be identified at the very earliest stages of crystallisation of the alloy.
An Experimental Comparison of Alternative Solid Forms for Savannah River High-Level Wastes
Authors: Stone John A.
Published: March 2011

Samples of borosilicate glass, high-silica glass, tailored ceramic, and SYNROC, incorporating simulated Savannah River high-level defense waste sludges, were leached by the MCC-1 procedure for times up to 28 days. Cesium, uranium, and cerium leach rates are reported for waste forms containing a composite sludge, at 40°C in deionized water, and at 90°C in deionized water, silicate water, and brine. The ordering of the waste forms from best to worst differs for each element leached, and none of the forms show a clear advantage for all the key radwaste elements. Some cesium leach rates for forms containing high-aluminum or high-iron sludges also are presented. So far, only small effects of sludge type have been observed, with one exception. This study is one of several inputs for selection of an alternative waste form for Savannah River waste.
The System SrMoO4-BaMoO4-CaMoO4: Compatibility Relations, The Implications for Supercalcine Ceramics
Authors: Scheetz Barry E. , Phelps Freeborn W. , Pepin John , White William B.
Published: March 2011

The stability of a tailored ceramic waste form under hydrothermal conditions was the subject of several previous papers [1,7–10] from this laboratory. One of the results reported in these studies was the apparent dissolution and reprecipitation of the alkaline-earth molybdate phases (scheelite-structure phase). The composition of the scheelite-structure phase after hydrothermal treatment was different from that before treatment (approximately Ca95 Sr5 after and Ca35 Sr40 Ba25 before). A schematic phase diagram was presented at that time to explain the results obtained.

This paper is a report of our attempt to experimentally determine the phase relations in the alkaline-earth molybdate (Ca, Sr, and Ba) and verify our previous interpretation. For this work, we prepared compositions throughout the ternary system and heated them at 1200°C for periods of 2 to 24 hours. The experimental products were characterized by x-ray diffraction and SEM/EDX examination.

At 1200°C, the two-phase solvus is nearly symmetric and extends from near the pure calcium and barium end-members to about 35 mole percent strontium at the critical point of the solvus. The increase in grain size, uniformity of composition within and between grains of the same phase and the approach to “textural equilibrium” in the 1200°C experiments all strongly suggest that equilibrium was attained.

New, calcium-rich compositions are suggested for the scheelite-structure phases in the supercalcine-ceramics based upon the interpretation of data from this study. This observation forces a re-examination of the assumption concerning the partitioning of Sr and Ba amongst the phases in the supercalcine-ceramic.
Study of Polyhalite from the Wipp Site, New Mexico
Authors: Brookins Douglas G.
Published: March 2011

Polyhalite (K2Ca2Mg(SO4).2H2o) is an important mineral present in the bedded evaporites of the WIPP site, southeastern New Mexico. Polyhalite contains two structurally bonded water molecules, and it is thus important to know if this mineral formed at or close to the time of sedimentation or, as proposed by others (1,2) more or less continuously throughout the Mesozoic and Cenozoic. If formed much later than original evaporite formation, then this implies a new source of water in order for polyhalite to form in turn raising questions about water abundance and mobility in the bedded evaporites. Polyhalite is not well suited for Rb-Sr geochronologic study becauseof the large amounts of common Sr (3), but it has been shown to be suitable for study by the K-Ar geochronologic methods(4). Pure polyhalites and those mixed with very small amounts of impurities yield K-Ar dates in the range of 200 – 220 MYBP and indicate little if any, loss of *40Ar. Polyhalites mixed with sylvite, halite, and (Na,K)Cl yield lower ages due to loss of *40Ar from the halides. Apparent age lowering is proportional to halide content and an extrapolated age of formation of near 225 MYBP results. Collectively, the K-Ar data convincingly show that the polyhalites formed at the time of sedimentation (except for isolated occurrences near dike intrusions) in Late Permian time. Finally, thermodynamic calculations, supported by petrographic study, show that polyhalite is often stable with respect to carnallite, sylvite and other minerals formerly thought to be older than polyhalite.
Predictions of Radionuclide Migration Rates for a Subseabed Repository
Authors: Brush L. H.
Published: March 2011

Geochemical research carried out by the U.S. Subseabed Disposal Program is described. Data from studies of high temperature interactions between sediments and porewater (seawater), and of sorption and diffusion of radionuclides in oxidized, deep-sea sediments are used, along with results from heat transfer studies, to predict migration rates of radionuclides in a subseabed repository.

Preliminary results for most radionuclides in oxidized sediments are very encouraging: fission products with moderate values of KD (generally 10 to 10 ml/g), and actinides with high values of KD (generally 103 to 106 ml/g) would not migrate significant distances before decaying to innocous concentrations. 137Cs, 90Sr, and 239Pu are among this group. The results for anionic species are less encouraging, but preliminary work with reduced sediments indicates that Tc can be effectively isolated.

Planning for a field verification of these laboratory and modeling studies is also described.
Solidification of Radioactive Wastes With Thermosetting Resin
Authors: Hayashi M. , Kobayashi K. , Okamoto O. , Kagawa T. , Wakamatsu K. , Irie H. , Matsuura H. , Yasumura K. , Nakayama Y.
Published: March 2011

Dried simulated radioactive wastes were solidified with thermosetting resin and their properties were investigated with laboratory scale and real scale products through extensive testings, such as mechanical resistance, resistance to leaching and swelling in water, radiation resistance, fire resistance and resistance to temperature cycling. The typical results were as follows: over 600 kg/cm2 of compressive strength, diffusion constant of ֮10−5 cm2/day for 137Cs leaching from solidified waste products, no significant change was found for up to 5 × 108 RAD irradiation, and damages were limited to the surface of the products after the thermal test and dropping impact test.
Processing of Titanates and Zeolites and use of a Cartridge System for ’Reactor‘ Wastes
Authors: Forberg S. , Westermark T. , Svärdströbm K. , FÄlth L.
Published: March 2011

New methods were introduced in order to facilitate the production of i) very coarse-grain pure mordenite at a large scale ii) mono-disperse sodium titanate of a low price also at small volumes, and iii) a composite ion exchanger with up to 20 W-% of mordenite in beads of sodium titanate.

Zeolites and titanates were converted to ceramic bodies by hot isostatic pressing at 1 300°C or by cold pressing followed by sintering at temperatures up to 1 300° C. Processed materials were zeolites, titanates and mixtures of them. The mechanical properties of sintered titanates were inferior to the hot pressed ones. Diffraction studies, static leaching at 40°C and Soxhlet leach tests were performed. The leach rates were much higher for mixed materials than for pure ones.

For the handling of inorganic ion exchangers through all processes from packing of inactive beds and immobilization of radioactive species to the sintering or hot pressing for final disposal a system of cartridges is suggested. A lay-out of the system is presented together with some special arguments and some practical experiences. Simple, safe and hygienic operations with an optimal use of the inorganic sorbents are expected to result from this system.
Immobilization of Savannah River High-Level Wastes in Synroc: Results From Product Performance Tests
Authors: Campbell John H. , Hoenig Clarence L. , Bazan Fernando , Ryerson Frederick J. , Rozsa Rudolf
Published: March 2011

Large samples (up to 15cm diameter) of SYNROC D containing simulated Savannah River (SRL) waste sludge have been prepared and performance tested. Waste loadings of 60-65 wt% for the SRL composite sludge have been achieved; this corresponds to a waste concentration (volumetric) loading of approximately 2.3-2.5 g/cm3. A typical SYNROC D sample has a density of about 4.0 g/cm3 with less than 0.2% porosity. The compressive and flexural strengths of SYNROC D are 51,200 and 9,400 psi, respectively and Young's Modulus is 20.1 × 106 psi by ultrasonic measurement. The quantity of respirable fines (less than 10 μm) generated during a constant energy density impact (10J/cm3) was less than 0.16 wt%. Values for the thermal conductivity (22°C) and the thermal expansion coefficient (22–950°C) were measured to be 1.7 W/m·K and 11 × 10−6 K−1, respectively. Normalized elemental leach rates determined by 28-day MCC-1 tests (90°C) for Cs, Sr, U and Nd are 0.7, 0.3, 5×10−5 and < 8×10−3 g/m2·d respectively.
Leaching Studies of Radionuclides from Solidified Wastes with Theremosetting Resin
Authors: Suzuki Kazunori , Kuribayashi Hiroshi , Morimitsu Wataru , Ono Isamu
Published: March 2011

This paper reports on studies of the leachability of Co–60 and Cs–137 from simulated LWR radwastes solidified with thermosetting resin and evaluates the effects of chemical fixation on leachability. It is concluded that insolubilization by a nickel-ferrocyanide compound offers an effective chemical fixation of these radionuclides and is a recommended pretreating method for radwastes that are to be solidified.
Rheological Characterization of Cementitious Grouts used to Dispose of Intermediate-Level Radioactive Waste By Hydrofracturing at Oak Ridge National Laboratory
Authors: Mcdaniel E. W. , Moore J. G.
Published: March 2011

The hydrofracturing process is a waste disposal process in use at the Oak Ridge National Laboratory for the permanent disposal of locally generated waste solutions. This process is now being modified for use in the disposal of sludge that results from the sodium hydroxide neutralization of acid waste solutions. In this process, the sludges will be slurried in a bentonite clay suspension and mixed with a solids blend of cement and other additives. The amount of dry solids required for each liter of waste slurry will be determined from a rheogram that relates the viscosity of the slurry with the grams per liter recommended for grouts with desirable flow properties.

A description of the process and the development of rheograms are included. Data are presented on the use of chemical additives to control the flow properties of grouts.
Tailored ion Exchange Resins for Combined Cesium and Strontium Removal From Soluble Srp High-Level Waste
Authors: Ebra Martha A. , Wallace Richard M. , Walker Darrell D. , Wille Roice A.
Published: March 2011

Novel organic resins that achieve high selectivities for both cesium and strontium have been synthesized. They are condensation polymers of resorcinol and formaldehyde withattached chelating groups. Their column performance compares favorably with that of commercially available resins for either cesium or strontium removal. By combining Cs+ and Sr2+ removal in the same bed, these resins can significantly reduce the size and complexity of proposed facilities for processing defense high-level waste.
Xps Valence State Determination of Np And Pu in Multicomponent Borosilicate Glass and Application to Leached 76–68 Waste Glass Surfaces
Authors: Karim D. P. , Lam D. J. , Diamond H. , Friedman A. M. , Coles D. G. , Bazan F. , Mcvay G. L.
Published: March 2011

Current plans for high-level radioactive waste disposal call for long term emplacement of canisters of a suitably leach resistant waste form in deep underground repositories. Proposed regulations [11] call for canisters with a designed lifetime of 1000 years. After this initial period, most of the remaining activity in the waste will be associated with the actinide elements. Thus, the leach behavior of the actinides takes on special importance. In particular, the leaching mechanisms must be understood if we are to attach any confidence to long term predictive extrapolation of short term leach tests. The actinides, unlike the rare earths, are not particularly similar in chemical behavior nor is their behavior reliably modeled by that of other elements. Thus, more studies directed toward the behavior of the actinides in candidate waste forms are important.
Nuclear Regulatory Commission Activities Related to High-Level Waste Materials Issues
Authors: Cook F. Robert
Published: March 2011

This paper describes the materials related activities of the Nuclear Regulatory Commission's (NRC's) staff in the area of high-level waste licensing of a geologic repository for nuclear waste. It frames these activities in the context of existing draft regulations for high-level waste disposal.
The Study of the Interaction of the Components of Imitator-Glasses of Glassified Radioactive Wastes With Various Surrounding Rocks
Authors: Spitsyn V. I. , Minaev A. A. , Barsova L. I. , Glazunov P. Ya. , Vetchkanov V. N.
Published: March 2011

This work is one of the first attempts to work out a proper technique for the determination of the diffusion of the phosphate glass components into various rocks by using X-ray microanalysis. Under study was thermal and radiationenhanced diffusion of phosphorus, chromium from phosphate glasses into the samples of basalt, metagabbro, metadunite and quartz at high temperatures (to 600°) during gamma irradiation. Radiation enhanced diffusion of ions into rocks.
Development of Sphene-Based Glass Ceramics Tailored for Canadian Waste Disposal Conditions
Authors: Hayward Peter J. , Cecchetto E.V.
Published: March 2011

Glass ceramics and ceramics based on minerals of proven thermodynamic stability in Canadian Shield groundwaters are being developed to host the wastes arising from future CANDU* fuel recycling. Sphene-based glass ceramics, produced by melti0n g Na2 O-CaO-Al2O3-TiO2-SiO2 compositions at 1400° C, cooling, ang then reheating the phaseseparated glasses to approximately 1000° C, show strong partitioning of waste ions into the sphene (CaTiSiO5 ) lattice. Leaching results suggest that these materials are durable in deionized water. In simulated groundwaters, the sphene phase appears to suffer no net leaching. Leach testing and manufacturing methods are discussed.
Structural Inhomogeneities in Silicate Glass
Authors: Bochynski Zenon
Published: March 2011

Low- and wide-angle X-Ray scattering methods were applied to determine the size of structural inhomogeneities in the surface and internal layers of silicate glass.

The functions of radial and cylindrical distribution of electron density in oxide glass, determined by Fourier-Bessel transformation method, were applied.

The corrected structural parameters (mainly distances and packing coefficients) were obtained enabling preliminary determination of the most probable space model of glass. Structural inhomogeneities appearing due to defects and local distortions of the components of elementary space structure of glass, were determined.

The method was applied in investigation of SiO2 in form of quartz glass and gel as well as the system SiO2-H2 O (hydrated gel). Them, it was transformed to investigation of a complex oxide glass (SiO2 -Na2 O-CaO-MgO-R2 O3).

In result of the analysis we obtained the structural parameters of glass (a1, a2, a3, … , an; Zcl, Zc2, Zc3, …, Zcn) as well as the parameters describing degree of crystallization, concentration and size of inhomogeneities.
Effects of Radiation Induced Defects on Laser-Induced Breakdown in SiO2
Authors: Soileau M. J. , Mansour Nastaran , Canto Edesly , Griscom D. L.
Published: March 2011

The effects of radiation damage on bulk laser-induced breakdown in Si02 were studied. Samples studied included Spectrasil A, B, and WF (water free). Measurements of laser-induced breakdown were conducted with 532 and 1064 nm laser pulses of approximately 30 nsec duration. Reductions of up to 50% in the laser-ind ced breakdown threshold were observed at 530 nm for samples exposed to 108 rads of γ-radiation.
Point Defects in Amorphous SiO2: What Have We Learned from 30 Years of Experimentation?
Authors: Griscom David L.
Published: March 2011

Point defects in amorphous silicon dioxide (a-SiO2) have been studied for over 30 years by numerous spectroscopic techniques, including optical absorption and emission and electron spin resonance (ESR). While all of these experimental approaches have yielded valuable insights, only ESR has afforded detailed atomic-scale structural characterizations. ESR spectra of two fundamental classes of defects in a-SiO have been knon since the 1956 work of Weeks. However, many crucial detaiis such as the 29Si and 17O hyperfine structures of these centers have been provided only within the past dozen years. From these results, it is known that the so-called E′ center comprises an unpaired electron in a dangling tetrahedral orbital of a single silicon atom at the site of an oxygen vacancy; at least three variants of the E′ center have been distinguished in a-SiO2. Two additional intrinsic defect types, the nonbridging oxygen hole center and the superoxide radical, have also been identified by ESR, these being relatively more prevalent in irradiated silicas of high and low hydroxyl contents, respectively. Recent theoretical developments have proven indispensible to the modeling of the E′ centers and have yielded valuable insights on the superoxide defects.
Transition-Metal Ions in Nd-Doped Glasses: Spectra and Effects on Nd Fluorescence
Authors: Stokowski S. E. , Krashkevich D.
Published: March 2011

We have measured transition-metal ion (Ti, V, Cr, Mn, Fe, Co, Ni, Cu) spectra and their effects on Nd fluorescence quenching in Nd-doped phosphate and silicate glasses. Our purpose was to determine the maximum allowable impurity content given particular limits on the absorption loss at 1053 nm and the Nd fluorescence quenching rate. To keep the absorption loss <0.1 m−1 the transition-metal impurity content should be kept below 0.5 ppmw. To keep the increase in the Nd fluorescence decay rate below 1%, the impurity content should be <3 ppmw. We have also found that the Nd quenching rates do not scale as predicted by the Forster- Dexter dipole-dipole energy transfer theory if we assume that the dominant variation with transition metal is the overlap integral of the Nd fluorescence spectrum and the transition-metal absorption. We suggest that phonon-assisted energy transfer to transition metals is effective in quenching Nd. We find that quenching rates increase 1.5 to 4 times as the Nd concentration increases from 0.5 to 10 × 1020 cm−2.
New Phosphorus Oxygen Hole Center in Γ-Irradiated SiO2:P2O5 Optical Fiber
Authors: Kawazoe H. , Kohketsu M. , Watanabe Y. , Shibuya K. , Muta K.
Published: March 2011

The formation of paramagnetic centers upon γ-irradiation was examined for the silica based waveguides doped with P2O5 by using ESR and optical absorption. The centers inherent in SiO2 glasses such as Si-E′ and OHC were found to be replaced with P-related centers such as phosphorus oxygen hole centers and phosphorus electron center by introducing a small amount of P2O5. New type of POHC was detected especially in the glass with [P2O5] of 1.3 mol % at 77K, which was assumed to be a precursor of the POHC stable at room temperature. The correlation between γ-induced loss-increase and the formation of these defects was examined.
Drawing- or Radiation-Induced Paramagnetic Defects Associated with Ge in SiO2:GeO2 Optical Fiber
Authors: Kawazoe H. , Watanabe Y. , Shibuya K. , Muta K.
Published: March 2011

ESR hyperfine structure produced by 73Ge of the drawing induced center in 10GeO2:90SiO2 or 30GeO2:70SiO2 fibers was detected and analyzed by taking into account site to site fluctuation in the glasses. The current assignment of the center to Ge-E′ in which an unpaired spin occupies one of sp3 hybrids of Ge was confirmed by the observation. The stress assisted radical cleavage of Ge-O bond was proposed to explain the enhancement of Ge-E′ formation in the fibers under quenching process. The hyperfine structure of the Y-induced center was also detected and similarly analyzed. New model structure was proposed for γ-induced center in which an electron is trapped on a Ge atom having four oxygen neighbors.
Mössbauer Spectroscopy – A Local Probe of Short and Medium Range Order in Network Glasses
Authors: Boolchand P.
Published: March 2011

Abtract

The principal defects in the stoichiametric chalcogenide glass GeSe2 are identified as hcapolar bonds which break the chemical order of the network. Glass compositional variation of this broken symmetry indicates that the hcmopolar bonds are not randcmly distributed in the network but dress edges of characteristic clusters. The cluster morphology is based on the layered structure of the stoichiametric crystalline ccmpound. The size of molecular clusters in the glass is found to be 50–75 Å
The Cross-Linked Chain-Cluster Model for Low Dimensional SixSe1−xInorganic Polymer Glasses
Authors: Griffiths James E.
Published: March 2011

Crystalline SiSe2and a series of SixSe1−xclear yelloworange glasses (0.33 × 0.40) were synthesized from the elements and were studied by Raman spectroscopy. Spectra of crystals were analysed in terms of the crystal structure of SiSe2whereas for the glasses a new cross-linked chain-cluster (CLCC) model is proposed and forms the basis of extensive spectral analysis. Extended chain only and random network models are inconsistent with the data. The CLCC model is characterized by well defined chains of edge-sharing (SiSe4) tetrahedra, as in the crystal, which are cross-linked via corner sharing (SiSe4) tetrahedra to form very large highly viscous inorganic polymers. The structure has considerable medium range order and provides for a self-consistent mechanism for transition to non-stoichiometric glasses in the range SiSe2to Si2Se3The smooth transition is monitored through spectral changes i the Si-Se vibrational stretching region from 150 to 300 cm and in the regiof of the collective modes at lower frequencies from 0 to 150 cm The frequencies and band contours of the latter dramatically track the introduction of disorder as the compositions move away from the stoichiometric SiSe2composition. The CLCC model is quite different from the raft model for GeSe2in some ways just as the crystalline structures of SiSe2and GeSe2differ from each other. Photoactivity in GeSe glass is one consequence of these structural differences in the two vitreous materials.
Intermediate Range Order in SixSe1−x Glasses
Authors: Susman S. , Johnson R. W. , Price D. L. , Volin K. J.
Published: March 2011

Six (chalcogen)1−x glasses represent a class of amorphous, binary, semiconducting solids of increasing theoretical and technological importance. In our laboratory, attention has been directed to these systems since they can form the basis of a remarkable series of fast ion conducting glasses. These vitreous materials are being considered as solid electrolytes for advanced electrochemical cells of high specific energy. For example, when stoichiometric SiS 2 is appropriately combined with Na2S, a Na-ion conducting glass results that has a room-temperature Na-ion conductivity that is several orders of magnitude greater than that of its oxide counterpart [1].The structures and defects present in these alkali-modified, ternary glasses are not known [2]. In fact, until recently, there has been a paucity of attention directed to the “simple” binary glass systems Si/S, Si/Se, and Si/Te. Therefore, four years ago, we began a systematic study of the structure and dynamics of Si xS1 SixSe1−x, and SixTe1−x covalent glasses. Of necessity, an interdisciplinary approach was adopted.
Dynamic Properties of Composite Materials Using a T-Matrix to Describe Microstructure
Authors: Varadan V. V. , Varadan V. K.
Published: March 2011

A dispersion equation is obtained for plane wave propagation in a discrete random medium. The effect of multiple scattering between the discrete inhomogeneities, statistical correlation in the position of the scatterers, details of the geometry, size and properties of the inhomogeneity via the T-matrix are considered. The resulting effective wavenumber for the average or composite medium depends on the above parameters and the frequency. The complex effective wavenumber in turn can be related to the effective properties of the composite material. The formalism is extremely well suited for numerical computation and can thus yield results suited for engineering applications. The other advantage is that the generality of the T-matrix description makes it convenient for describing acoustic, electromagnetic and elastodynamic problems.
Hunting Magnetic Phases with Total-Energy Spin-Polarized Band Calculations
Authors: Marcus P. M. , Moruzzi V. L. , Schwarz K.
Published: March 2011

Comments are made on total energy band calculations as tools for exploring properties of solids; the importance of fixed spin moment calculations is noted. Use of energy - magnetisation curves to locate magnetic phases is described. Detailed results for fcc and bcc Co and Ni and phase diagrams on the magnetisation - volume plane exhibit two new phases for each metal and show that ferromagnetic fcc Co and bcc Ni break down at small volumes and make first order transitions to nonmagnetic phases in a metamagnetic volume range.
Monte Carlo Simulation of Growth of Crystalline and Amorphous Silicon
Authors: Dodson Brian W. , Taylor Paul A.
Published: March 2011

The authors have previously introduced a method, based on Monte Carlo techniques, for simulation of crystal growth processes in a continuous space. We have applied the method, initially used to simulate growth of two-dimensional Lennard-Jones systems, to treat growth of silicon in three dimensions. The interaction model for silicon is taken to be the recently introduced Stillinger-Weber (S-W) potential, which is a two- and threebody classical potential. Although the early stages of growth seem to be well modelled by the S-W potential, growth of even a single monolayer of epitaxial (111) silicon does not seem to be possible. Modifications to the S-W potential were considered, and found to be unacceptable physically. More accurate treatment of non-ideal atomic configuration energies is necessary to arrive at physically realistic growth simulations.
A Highly Parallel Computer for Molecular Dynamics Simulations
Authors: Auerbach D. J. , Bakker A. F. , Chen T. C. , Munshi A. A. , Paul W. J.
Published: March 2011

We are constructing a highly parallel computer array well suited to the requirements of molecular dynamics simulations of the behavior of large systems of interacting particles. A tightly coupled message passing structure is used based on a specially designed processor with 12 MFLOPS peak performance. High speed synchronous communication over a full permutation network and hardware support for operations important in molecular dynamics codes are also provided. An analysis of this configuration indicates that efficient use can be made of 1000 processors working simultaneously.
Cooperative Premelting Effects on a (110) FCC Surface: A Molecular Dynamics Study
Authors: Rosato V. , Pontikis V. , Ciccotti G.
Published: March 2011

The thermodynamicaL and structural behavior of a (110) face of a (12–6) Lennard-Jones fcc solid has been investigated by MoLecuLar Dynamics computer simulation on the solid-gas coexistence Line up to a temperature T= 0.94 TM (TM: melting point). We have found evidence for cooperative defect production on free surfaces which Leads to a structural transitiDn above T≈0.7 TM. This transition is studied using as an order parameter the excess energy for surface Layers due to missing bonds parallel to the surface with respect to the bulk. Furthermore we report the vaLues of the mean square displacement for surface and bulk atoms as a function of temperature. Despite their high values at the surface, surface Layers are not molten but only highly disordered above the transition temperature.
Calculations of Resistivity and Superconducting Tc in Transition Metals
Authors: Allen P. B. , Beaulac T. P. , Khan F. S. , Butler W. H. , Pinski F. J. , Swihart J. C.
Published: March 2011

A survey is given of various electron-phonon effects which have been vcalculated for the metals Nb, Mo, Ta, Pd, and Cu. These effects include the mass enhancement γ, superconducting Tc, electrical and thermal resistivity, Hall coefficient, magnetoresistance, and the successfully tested predictions of linewidths yQ of phonons. The calculations use local density approximations (LDA) energy bands, experimental phonons, and the rigid muffin tin (RMT) approximation. Mesh size noise is less than 1% and the Bloch-Boltzmann integral equation has been solved to unprecedented accuracy.
Thermal Wave Inspection in IC Manufacturing
Authors: Rosencwaig Allan
Published: March 2011

We describe a highly sensitive, noncontact method for inspecting important, but previously difficult to monitor, processes used in the manufacture of integrated circuits. This technique, based on the detection of thermal waves through laser-induced modulation of the sample's optical reflectance, has proven to be an excellent means for detecting and quantifying the extent of lattice damage or disorder in silicon and gallium arsenide wafers that results from chemopolishing, ion implantation and etching processes. This technique thus provides a powerful and cost effective method for monitoring the quality of incoming wafers, the dose and uniformity of ion implantations and the efficiency and uniformity of dry etch processes. Furthermore this method may be used on actual product wafers as well as test wafers since the measurements are performed in a completely nondamaging fashion and with micronscale resolution.
Interface Resolution in Auger Depth Profiling
Authors: Coulman D. , Turner A.
Published: March 2011

It has been well established that sputtering artifacts such as ion beam mixing, preferential sputtering and cone formation ultimately limit interface resolution in Auger and ESCA depth profiling. We have conducted a comparision of the effect of sample rotation, and of the angle of incidence of the ion beam using one and two ion guns on interface resolution. Our investigation has concentrated on the interface resolution and detection of impurities at the various interfaces of a typical semiconductor metallization scheme [Al 700 nm/ TiW 100 nm/ Si02 100 nm/Si]. We have determined that in going from a standard sputtering geometry of a 67 degree tilt from the surface normal to 80 degrees one obtains a factor of five improvement in interface resolution. Sample rotation, on the other hand, was found to improve interface resolution by a factor of two at 67 degrees and to result in minor improvement at 80 degrees. The effect of two ion guns was found to have a negligible effect on the samples studied.
Relative Lattice Parameter Measurement in Quaternary (InGaAsP) Layers on InP Substrates Using Convergent Beam Electron Diffraction
Authors: Twigg M. E. , Chu S. N. G. , Joy D. C. , Maher D. M. , Macrander A. T. , Nakahara S. , Chin A. K.
Published: March 2011

With X-ray diffraction techniques, it is possible to routinely measure lattice parameters to several parts in 104 for macroscopic specimens. However, measurements of lattice parameter changes for quaternary (InGaAsP) device structures several microns in width are not usually feasible with X-ray diffraction techniques. Convergent Beam Electron Diffraction (CBED), which is one of the techniques available on a modern transmission electron microscope (TEM), may be sensitive to these small, localized lattice parameter changes. Unfortunately, dynamical diffraction effects prevent direct extraction of changes in the lattice parameter from CBED patterns which are obtained from high atomic number materials. For this reason, we have chosen to calibrate the relative position of CBED features with X-ray lattice parameter measurements which were obtained from planar quaternary layers grown on InP substrates. For the active quaternary region of an electro-optical device structure, it is shown that this approach may be sensitive to a relative change in the lattice parameter as small as ±2 parts in 104, which is the uncertainty in the X-ray calibration measurements.
Electron Optical Characterization of Amorphous SIC:H CVD Films
Authors: Fisher R. M. , Posthill J. B. , Sarikaya M. , Reimer J. A. , Petrich M.
Published: March 2011

The utility of various electron optical methods to characterize the microstructure and composition of thin films of amorphous silicon-carbon films formed by plasma-activated CVD of SiH4 and CH4 has been investigated. The techniques employed include conventional and high resolution transmission electron microscopy and diffraction, non-dispersive x-ray spectroscopy and electron energy loss spectroscopy.
A New Technique for High Speed X-Ray Double Crystal Rocking Curve analysis
Authors: Tanner B. K. , Xi Chu , Bowen D. K.
Published: March 2011

A novel technique for high speed X-ray double crystal rocking curve analysis of epitaxial layers is described. It employs specimen rotation about an axis almost normal to the Bragg planes in order to optimize Bragg plane tilts. Very rapid set-up is possible by peak searching using this rotation axis rather than the standard ω scan. A rotation stage suitable for a Bede Scientific Instrument Model 6 diffractometer is described and its performance assessed. Experimental and theoretical values of the shift in centroid of the ω scan rocking curve as a function of rotation angle are in excellent agreement.
Scattering and Absorption of Infrared Light on EL2 Clusters in GaAs Semi-Insulating Materials
Authors: Fillard J. P. , Castagne M. , Bonnafe J. , Gall P.
Published: March 2011

It is known that dislocations and EL2 clusters participate in infrared transmission images. Optical quenching of the typical cell patterns at low temperature also charge EL2 with contributing to images. A point yet is not clearly established: such optical contrast could originate in a quantum absorption process or as well in a scattering of the photons. This paper aims at showing that both optical processes are likely to occur in most of the GaAs SI samples and that the two phenomenons can be considered as localy correlated. So monitoring EL2 center density by optical “absorption” could be a trap for the unwarry.
A Rapid, Precise Measurement of the Thickness and Compcsiticn of Multilayer Metalfilms
Authors: Linier Robert E. , Klainik G. , Augenstine J.
Published: March 2011

We have developed general algorithms for interpreting X-ray fluorescence data from single and multilayer metal films to yield precise values for both thickness and composition. As an example, the precision for replicate analyses of a Permalloy sample was measured to be 0.07 weight % Ni (1σ). The thickness was measured to be 1.387 ± 0.005 microns, a 1σ precision of 0.3% relative. Several examples will be presented.

The fundamental parameter algorithms are quite general and are capable of dealing with variable compositions in each of the films in a multilayer stack. The only restrictions are that: 1) Each element analyzed must appear only once in the films or substrate, and 2) The signal from each element is not obscured by that of another element. The accuracy and precision of the measurement is improved if a substrate signal is observed.
Variable Angle of Incidence Spectroscopic Ellipsometric Study of Semiconductor Multilayer Structures
Authors: Snyder Paul G. , Woollam John A. , Alterovitz Samuel A.
Published: March 2011

The sensitivity of spectroscopic ellipsometry data to multilayer model parameters is shown to be a strong function of the angle of incidence. A quantitative study for a GaAs-AlxGa1-xAs-GaAs structure shows that maximum sensitivity to layer thicknesses and ternary composition occurs near the wavelength-dependent principal angle. These results are verified by experimental measurements on two MBE-grown samples. Moderately high doping levels in the ternary layers are also found to strongly affect the data at photon energies below the ternary bandgap. Null ellipsometry measurements at only two wavelengths are sufficient to determine layer thicknesses.
A New Application of Rbs-Pixe with High Energy Microbeam
Authors: Raicu B. , Bakhru H. , Fesseha S. , Gibson W. M.
Published: March 2011

A beam of 2 MeV He+ ions with a diameter of 2 microns was used to perform Rutherford backscattering (RBS) and particle induced x-ray emission (PIXE) analysis on large residual defects formed by high dose arsenic (As) ion implantation and furnace annealing. Research results concerning contamination in implanted silicon wafers generated by primary beam sputtering, inadequate wafer transport system, and other technological factors are presented.
Proton Induced Kossel Diffraction of X-Rays in Copper
Authors: Rickards C. Jorge
Published: March 2011

A 700 keV proton beam was used to induce the emission of X-rays in a single crystal copper target. The X-rays are diffracted inside the target, giving rise to a large number of lines, which were recorded on photographic film. The presence of certain lines and the absence of others, as well as the variable intensity along the lines, are explained qualitatively with a kinematical approach.
Secondary Ion Imaging with a CCD Camera
Authors: Anthony J. M. , Farrington D. L. , Gove R. J.
Published: March 2011

A digital image processing system based on a charge-coupled device (CCD) camera interfaced to a Texas Instruments Professional Computer (TIPC) has been implemented on the Cameca IMS-3F Ion Microscope to improve lateral imaging capabilities. The CCD sensor, produced at TI, generates a 376 × 288 pixel image, and a hardware interface to the TIPC provides an 8-bit grayscale (256 levels) for subsequent storage and display. The Cameca ion microscope projects secondary ions from the sample onto a microchannel plate/fluorescent screen combination. The CCD array images the screen directly and no vacuum modifications to the Cameca are required. Nitrogen cooling of the CCD imager to reduce thermal noise allows low light levels to be integrated for several minutes and displayed on the TIPC, providing a substantial increase in sensitivity over the standard optics. False color imaging enhances the contrast of various features in the ion image to provide ease of identification. A variety of software options, such as frame mosaicking, multiple frame overlays, color threshold modification and histogram equalization are available. The TIPC has also been interfaced to the Cameca controlling computer to allow display of ion images during depth profiling.
Quantitative Distribution Analysis of Phosphorus with Sims in the Layer System SiO2/Si
Authors: Stingeder G. , Traxlmayr U. , Guerrero E. , Grasserbauer M. , Pötzl H.
Published: March 2011

The measurement technique for quantitative distribution analysis of P in the layer system SiO2/Si was optimized. Oxygen primary ions and an increased oxygen pressure ( 5.10E-5mbar) in the sample chamber were used for elimination of the matrix effect.A computer routine for precise adjustment of the mass spectrometer during depth profiling with high mass resolution was developed. Charging effects were compensated by flooding the sample with electrons, optimized biasing of the accelerating potential of the secondary ions and normalization to a reference signal. The improved measurement technique was used for determination of segregation coefficients which are used as input parameters for process modeling in MOS transistor production.
Modulating Functions Waveform Analysis of Multi-Exponential Transients for Deep-Level Transient Spectroscopy
Authors: Ransom C. M. , Chappell T. I. , Freeouf J. L. , Kirchner P. D.
Published: March 2011

An improved method for the analysis of multi-exponential transients with high resolution has been applied to DLTS. Full-waveform fittings, using the technique of Modulating Functions, are made to digitized transients captured by a computer. This technique is described and results for both simulated data (with noise) and real data are shown. The advantages over previously published techniques in resolution, calculation speed, insensitivity to truncation error and noise are discussed. Also, how this method allows for a determination of the number of components is presented.
Multi-Exponential Analysis of DLTS by Contin
Authors: Morimoto Jun , Kida Tatsuo , Miyakawa Toru
Published: March 2011

Deep level transient spectroscopy (DLTS), which assumes a single exponential decay form for the transient junction capacitance, is the most commonly used method to characterize deep impurity levels in semiconductors. However conventional DLTS may lead to erroneous results if there are several closely spaced energy levels or the emission rate has a continuous spectrum. To overcome this difficulty a novel method named the multi-exponential analysis of DLTS by CONTIN (MEDLTS by CONTIN) is proposed. This method analyzes the emission rate to have a finite continuous spectrum S(λ) which appears in the transient junction capacitance C(t)=, by using the program “CONTIN” developed by Provencher in biophysics. Even if S(λ) includes two peaks at λ1 and λ2, those peaks can be distinguished for λ2/ λ1>2. As an example of the application of this method, deep levels in Si:Au were experimentally investigated. According to the three dimensional S(λ)-T2/λ-1/T representation, the single peak in the conventional DLTS was clarified to consist of two adjacent levels with activation energies and capture cross sections EB1=0.51eV, σB1=4.0×10−15cm2 and EB2=0.47eV, σB2=1.1×10−15cm2. With the assumption of the finite continuous spectrum S(λ) for the emission rate, MEDLTS by CONTIN permits one to get much information correctly. MEDLTS by CONTIN is superior to the conventional DLTS because it is a single-temperature scan, multi-exponential analysis instead of the conventional multi-temperature scan, single-exponential analysis.
Contactless Spatially Resolved Measurement of Bulk Free-Carrier Lifetime in Silicon Ingots
Authors: Johnson S. M. , Johnson L. G. , Hemphill R.
Published: March 2011

A contactless spatially resolved measurement of bulk free-carrier lifetime in polycrystalline silicon ingots was accomplished using optically modulated free-carrier infrared absorption. Using a CW Nd:YAG laser (λ = 1.319 μm) for a probe and novel pulsed, tunable, infrared dye laser (λ = 1.10 to 1.13 μm) with photon energies near the Si bandgap, for a pump, the free-carrier lifetime was determined from transient absorption measurements to a maximum depth of 3.0 cm from the surface of an ingot. The spatial dependence of the free-carrier lifetime and the distribution of precipitates (determined from infrared probe transmission measurements) measured along the growth axis of an ingot were found to be strongly related to the spatial dependence of the I–V characteristics of large area solar cells fabricated from the subsequently wafered ingot.
Neutron-Zwischenreflex-Scattering from Point Defects in Crystals
Authors: Dosch H. , Peisl J.
Published: March 2011

Diffuse neutron or x-ray scattering close to the Bragg peaks (Huang scattering) and far away from Bragg peaks (Zwischenreflex-scattering) supplies detailed information on point defects and small agglomerates in crystals [1]. The defect structure, i.e. the lattice location, the displacements of the near neighbours and the strength and symmetry of the long ranged displacement field can be determined. In order to demonstrate the power of this technique, we report on recent experimental results. Interstitially dissolved N and O in Nb are located on octahedral sites and create rather large displacements in their vicinity. Their long ranged displacement field shows the symmetry of the defect site. The light interstitials H and D in Nb are located on tetrahedral sites and their long ranged displacement field shows the symmetry of the host lattice. A rather complicated defect model is necessary in order to explain the local defect structure.