bluuebunny/crossref_metadata_2025_split huggingface dataset:
Point Defects in Amorphous SiO2: What Have We Learned from 30 Years of Experimentation?
Authors: Griscom David L. 
Published: March 2011

ABSTRACTPoint 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

ABSTRACTWe 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

ABSTRACTThe 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

ABSTRACTESR 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

AbtractThe 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

ABSTRACTCrystalline 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

ABSTRACTSix (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

ABSTRACTA 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

ABSTRACTComments 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

ABSTRACTThe 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

ABSTRACTWe 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

ABSTRACTThe 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

ABSTRACTA 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

AbstractWe 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

AbstractIt 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

AbstractWith 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

AbstractThe 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

AbstractA 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

AbstractIt 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

AbstractWe 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

AbstractThe 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

AbstractA 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

AbstractA 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

AbstractA 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

AbstractThe 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.