bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impurity Effects of Metal Ions in Chalcogenide Glass Films
Authors: Suzuki M. , Okano S. , Machi S. , Yamakawa H. 
Published: March 2011

ABSTRACTDoping effects of metal ions in chalcogenide glass films were studied. Doped impurities were found to act as donor or acceptor centers, when impurity ions were introduced in chalcogenide glass films below the glass transition temperature. Rectifying effects were realized in chalcogenide glass films doped with Al, Cd and Mg, so it is certain that the p-n junction was formed by the impurity doping. The tunneling of electrons through gap states, however, appeared to increase the reverse current of heavily doped diodes, so that large rectifying effects were not attained. A high density of defect states especially in the surface region would be responsible for low temperature diffusion of metal ions.
Defects in Gel-Derived Glasses
Authors: Brinker C. J. , Tallant D. R. , Roth E. P. , Ashley C. S. 
Published: March 2011

ABSTRACTDefects in gel-derived glasses were reviewed for the three principal stages of the sol-gel process: solution, porous gel, and consolidated glass. The most prominent defects in gel-derived SiO2 are Raman active defects characterized by sharp bands at 490 cm−1(D1) and 608 cm−1(D2) 18O enrichment, experimental estimates of heats of formation, and structural studies of cyclic model compounds were used to identify the structural origins of D1 and D2 in gels. We conclude that D1 and D2 in gel-derived SiO2 are the oxygen breathing modes of 4- and 3-fold siloxane rings, respectively, as originally proposed by Galeener to explain these Raman-active defects in conventional vitreous silica (v-SiO2). During heat treatments near Tg (defined by n = 1013.5 poises), the gel-derived SiO2 structure rapidly approaches that of conventional v-SiO2.
The Nature of the Paramagnetic States in SiO2-GeO2-Sol-Gel Glasses
Authors: Kordas George , Mukherjee S. P. 
Published: March 2011

ABSTRACTThe 9.5 GHz ESR-spectra of gamma-ray irradiated 94 SiO2 6 GeO2 (mol%) aero gels heat treated at 462°C were recorded at 300 K. The ESR-spectrum of this gel consisted of an asymmetric line (g1 = 2.001, g2 = 1.995, and g3 = 1.994) attributed to the Ge(3)-center and other components which have not yet been identified. The 94 SiO2 6 GeO2 gel was treated at 1000 and 1280°C and then exposed to gamma-ray radiation. The Ge(1)- and Ge(3)-centers were identified in the 94 SiO2 6 GeO2 gel with TH = 1000°C. At TH = 1280°C the signal of the Ge(1)-center dominated the spectrum of this sample. The spectra of the 58 SiO2 42 GeO2 gels with TH = 1200 and 1400°C can be described by the Ge(3)-center. The Ge(1)-center was of minor importance in these samples.
The Thermal Conductivity of Several Fluoride Glasses
Authors: McCarthy K. A. , Sample H. H. , Koss M. B. 
Published: March 2011

ABSTRACTThe thermal conductivities of beryllium fluoride glass and a fluoroberyllate glass have been measured in the 2–100K temperature range. These results are compared with earlier results on fluorozirconate glasses. The “plateau” region is well-defined for both materials. The plateau-center conductivity for BeF2 glass is the lowest yet recorded for any glass; it is some three times lower than the fluoroberyllate glass and four times lower than the fluorozirconates. A preliminary analysis of the data show a strong correlation between plateau-center conductivity and average cation mass of the material.
Structural, Electronic, and Magnetic Properties of Surfaces, Interfaces, and Superlattices
Authors: Freeman Arthur J. , Fu C. L. , Oguchi T. 
Published: March 2011

ABSTRACTAdvances in all-electron local density functional theory approaches to complex materials structure and properties made possible by the implementation of new computational/theoretical algorithms on supercomputers are exemplified in our full potential linearized augmented plane wave (FLAPW) method. In this total energy self-consistent approach, high numerical stability and precision (to 10 in the total energy) have been demonstrated in a study of the relaxation and reconstruction of transition metal surfaces. Here we demonstrate the predictive power of this method for describing the structural, magnetic and electronic properties of several systems (surfaces, overlayers, sandwiches, and superlattices).
Pseudopotential Calculations of Structural Properties of Solids
Authors: Cohen Marvin L. 
Published: March 2011

ABSTRACTThrough the development of a total energy pseudopotential approach, it has become possible to compute structural, electronic, and vibrational properties of solids using only the atomic numbers and atomic masses of the constituent atoms as input. The method has been applied to semiconductors, insulators, and metals; and agreement with experiment for most properties is usually within a few percent.Applications include the determination of lattice constants for specific structural phases, properties of structural phase transitions, cohesive energies, bulk moduli, lattice vibrational spectra, electron-lattice interaction parameters, and electronic and superconducting properties. A recent example is the prediction of superconductivity in highly condensed hexagonal silicon which was subsequently found experimentally.
Fracture and Flow Via Nonequilibrium Molecular Dynamics
Authors: Hoover W. G. , De Lorenzi G. , Moran B. , Moriarty J. A. , Ladd A. J. C. 
Published: March 2011

ABSTRACTThe scope of molecular dynamics problems designed to simulate materials properties is described, focussing on the limits computation imposes on space and time scales, as well as the limits theoretical understanding imposes on our knowledge of interatomic forces. Five strategies for improving the efficiency of the simulations are described. Shock-induced solid-solid phase transformations are discussed to illustrate these ideas.
Electronic Properties of Liquid Silicon
Authors: Broughton J. Q. , Allen P. B. 
Published: March 2011

ABSTRACTThe electronic properties of liquid silicon were computed by coupling molecular dynamics and tight binding methods. By employing the Stillinger-Weber potential, atomic configurations of liquid Si at 1740°C were generated by molecular dynamics. Tight binding parameters chosen to fit fcc,bcc, simple cubic and diamond cubic band structures of silicon, were then used to obtain the electronic properties of the system. All states within 10eV of the Fermi level are found to be delocalized, the density of states spectrum similar (but much broadened) to that of diamond cubic silicon and the optical conductivity is found to be almost featureless with no Drude behavior.
Interatomic Forces and Structure of Grain Boundaries
Authors: Vitek V. , de Hosson J. Th. M. 
Published: March 2011

ABSTRACTOver the past two decades, grain boundary structures have been investigated, with increasing frequency, using computer simulation techniques. The accuracy of the potentials used to describe the interaction between atoms is essential to the success of any computer modelling and practically all these studies have been made assuming that the atoms exert pair-wise forces on each other. This paper discusses the applicability and limitations of this assumption and the validity and applicability of the simulation results obtained with pair-potentials. First, it is shown that certain structural features of grain boundaries are independent of the potential used. Such results form, for example, the basis of the structural unit model which relates the structures of boundaries corresponding to different misorientations. Secondly, the multiplicity of boundary structures and its physical implications are discussed. In particular, we report on the complexities of the structure of Σ=5 [001] twist boundaries and on alternative structures of [111] twist boundaries near the Σ=3 twin orientation, both found by computer modelling. These results, which are of general nature, are compared with experimental observations by X-ray diffraction and transmission electron microscopy and a very good agreement is found. However, exact positions of atoms in calculated structures depend on the potential used. Hence, to study properties sensitively dependent on these positions requires to go beyond the pair-potentials.
Surface Reconstruction of SI(100)
Authors: Weber Thomas A. 
Published: March 2011

ABSTRACTThe reconstruction of the Si(100) surface has been studied using a potential consisting of two- and three-body interactions [1]. Minimum energy quenches of a slab of 320 Si atoms 10 layers thick with periodic boundary conditions in the xy plane found the p(2×l) reconstruction lower in energy than the c(2×2) reconstruction. The potential energy contours for the addition of an adatom to the (100) surface were determined for the unreconstructed surface and for the p(2×l) and c(2×2) reconstructions.
Progress in Spin Glasses and Random Fields – Research with a Special Purpose Computer
Authors: Ogielski A. T. 
Published: March 2011

ABSTRACTExtensive numerical simulations of random magnetic materials have been recently performed at AT&T Bell Laboratories with a fast specially designed computer. I will discuss certain issues concerning the use of specialized computers in research, and I will review some major results obtained in simulations of a three-dimensional spin glass and an antiferromagnet with random fields.
Hartree-Fock Cluster Computations for Ionic Crystals
Authors: Vail J. M. , Pandey R. 
Published: March 2011

ABSTRACTThe ICECAP code is applied to charged and uncharged color centers in alkali halides and alkaline-earth oxides, to test the usefulness of complete-cation pseudopotentials for reproducing the cluster boundary conditions. The physical model includes consistency up to electrostatic octupole order between the Hartree-Fock cluster and the surrounding infinite shell-model lattice. The total energy of the system is determined variationally, including distortion and polarization of the cluster and lattice, and LCAO-MO gaussian-localized cluster wave functions. Electronic states with the lattice unrelaxed are also analysed, yielding color-center optical transition energies. Furthermore, consistency between quantum (cluster) and classical (shell-model) descriptions of the perfect lattice is tested.
Theoretical Investigation of the Jahn-Teller Vibronic 1E ⊗ ɛ State in the Neutral Vacancy of Silicon
Authors: Malvido J. C. , Madhavan P. V. , Whitten J. L. 
Published: March 2011

ABSTRACTA method for constructing Jahn-Teller coupled vibronic states is developed by projecting distorted electronic eigenstates onto undistorted states and, with the aid of irreducible tensor methods, the force constants can be identified with reduced matrix elements of the normal mode expansion of the vibrational Hamiltonian. A scheme is then realized for estimating the force constants as well as the total vibronic energy from the calculated energie of the distorted electronic states. An application of the method to the 1 E ⊗E vibronic state of the neutral silicon vacancy is presented as an illustration
Vibrational Properties of the π-Bonded Chain Model of the Si(111)2×l Surface
Authors: Alerhand O. L. , Allan D. C. , Mele E. J. 
Published: March 2011

ABSTRACTA tight-binding theory is used to study vibrational excitations of the π-bonded chain model of the Si(111)2×l surface. Some aspects of the surface phonon spectrum are discussed. We study the charge fluctuations driven by the vibrational excitations and the surface conductivity associated with the phonons. We find that a longitudinal optical phonon on the surface chains dominates the surface conductivity.
Defect Behaviour in Oxides
Authors: Cormack A. N. , Catlow C. R. A. , Lewis G. V. , Freeman C. M. 
Published: March 2011

ABSTRACTWe describe computer-based atomistic simulation studies of defect behaviour in oxides. In illustrating the value of the technique, contact with experiment is discussed through comparison with measured energies of ion migration and other energies. Since the success of these methods is dependent on the extent to which the interatomic potentials used provide a realistic model of the material, consideration is given to transferability of potentials, especially to tenary compounds where the widely adopted practice of fitting potential parameters to available crystal data is not feasible. Our principal examples will include ionic conductivity in gadolinium zirconate, electronic defect properties of BaTiO3 and grossly nonstoichiometric rutile.
Simulation of Equilibrium Segregation in Alloys Using the Embedded Atom Method
Authors: Foiles Stephen M. 
Published: March 2011

ABSTRACTThe Embedded Atom Method (EAM) is combined with Monte Carlo simulation techniques to determine the equilibrium segregation at internal defects and surfaces. This approach has been applied in the Ni-Cu alloy system to the calculation of the surface composition profiles and the segregation at an edge dislocation. The surface composition profile of these alloys as a function of distance from the surface is found to vary non-monotonically with the top atomic layer strongly enriched in Cu and the near surface atomic layers enriched in Ni. The compositional variation in the core region of an edge dislocation shows enrichment of Ni in the compressed regions of the partial dislocation core and Cu enrichment in the expanded regions. In addition, the composition changes abruptly at the slip plane of the dislocation.
Defect Structure and Dynamics in Silicon
Authors: Pantelides S. T. , Car R. , Kelly P. J. , Oshiyama A. 
Published: March 2011

ABSTRACTThis paper gives a brief account of recent calculations of equilibrium configurations, formation energies, and migration energies of intrinsic lattice defects (vacancies, self-interstitials) and complexes of dopant impurities (phosphorus, aluminum) with these defects. The results have been used to provide a comprehensive interpretation of low- and high-temperature diffusion data.
Depth-Profiling of Near-Surface Atomic Correlations by Total Reflection of Synchrotron Radiation
Authors: Dosch H. , Wack D. C. , Batterman B. W. 
Published: March 2011

AbstractWe report measurement of Bragg intensities obtained from an Fe3Al(110) single crystal under the condition of total reflection. It is demonstrated that depth-resolved near-surface atomic correlations can be achieved by the independent control of both ocurring grazing angles.
Scanning Optical Fiber Microscope for High Resolution Laser Beam Induced Current Images of Semiconductor Materials
Authors: Ogura M. , Tajima M. , Tokumaru Y. 
Published: March 2011

AbstractLaser beam induced current images (LBIC) of polycrystalline silicon and liquid encapsulated Czochralski (LEC) GaAs are observed with a new scanning optical fiber microscope (SOFM), which utilizes an optical fiber as a mobile light source. In this system, fine optical probing with the beam diameter less than lm is achieved without requiring severe mechanical precision. A variety of light sources are employed to reveal different defect species. The distribution of deep levels in LEC GaAs is visualized with extrinsic photo-excitation by using a Nd:YAG laser.
Channeling Contrast Microscopy: A Powerful Tool for Examining Semiconductor Structures
Authors: McCallum J. C. , Brown R. A. , Nygren E. , Williams J. S. , Olson G. L. 
Published: March 2011

AbstractChanneling contrast microscopy with a He+ microbeam has been employed to measure 3-dimensional damage distributions and impurity profiles in ion implanted laser annealed silicon. Refinements to the technique are described, involving construction of a precision goniometer to allow accurate orientation of the microbeam with respect to micron-scale- sample features. We have found that indium diffusion in amorphous silicon is significantly less for laser annealing than with lower temperature furnace annealing. Lateral variations in the extent of crystal growth have also been observed across laser irradiated areas less than 100μm.
Characterization of the DFZ in Silicon Wafers by a Non-Destructive Technique
Authors: Borrego J. M. , Gutmann R. J. , Jensen N. , Lo C. S. , Paz O. 
Published: March 2011

AbstractThis paper presents a non-destructive technique for characterizing The Defect Free Zone (DFZ) of silicon wafers. The method consists in measuring the decay of microwave reflection following the creation of excess carriers by a light pulse. For wafers with similar surface passivation we have found a direct correlation between the transient duration and the size of the DFZ. A computer model of the microwave reflection in silicon wafers with different size of DFZ agrees with experimental observation.
Microstructural Characterization of GaAs Substrates
Authors: Moore T. M. , Matteso S. , Duncan W. M. , Matyi R. J. 
Published: March 2011

AbstractThe defect microstructures of GaAs substrates have been investigated in a multi-technique approach including integral cathodoluminescence (CL), scanning electron acoustic microscopy (SEAM), double crystal x-ray topography (XRT), and defect delineation etch. The XRT, CL, and SEAM studies are of identical areas on
<100> SI GaAs(Cr) grown by the liquid encapsulated Czochralski (LEC) method and by the horizontal Bridgman (HB) method. Correlation was made to the defect structure revealed by defect delineation etching. The samples were also characterized by Fourier transform photoluminescence (FTPL) to qualitatively identify the major transitions contributing to the CL images. The CL, SEAM, XRT, and defect delineation etch images of each material are compared and their different perspectives are discussed.
Recent Progress with Surface Analysis by Laser Ionization
Authors: Becker Christopher H. 
Published: March 2011

AbstractThis paper briefly reviews previous results and developments, then presents new results, using a novel surface analytical technique that uses non-resonant multiphoton ionization (MPI) of neutral atoms and molecules sputtered by an ion beam, or desorbed by an electron beam or laser beam. In this method, which we call surface analysis by laser ionization (SALI), the non-resonant MPI, or “laser ionization,” is coupled with state-of-the-art time-of-flight mass spectrometry to provide extremely sensitive, general, and readily quantifiable surface analysis. Examples are presented for two applications relevant to the semiconductor industry and for the analysis of the near surface region of two specially pretreated stainless steels. A discussion also describes the favorable prospects for implementation of SALI with submicron dimension liquid metal ion beams for microanalysis, including situations with electron beam sensitive samples.
Ion Beam Channeling in Superlattices
Authors: Chu Wei-Kan , Allen W. R. , Picraux S. T. , Ellison J. A. 
Published: March 2011

AbstractIon beam channeling analysis has recently been applied to lattice strain measurements on strained-layer superlattices (SLS). In this review talk, we outline three different methods of strain measurement: axial dechanneling, angular scans, and planar resonance. We describe the principles and illustrate them with examples; we also give a detailed theoretical treatment of the planar resonance effect in SLS's.
Pulsed Beams and Ion-Beam Mixing: Metal-Si and Metalmetal Structures
Authors: Mayer J. W. , Fastow R. , Galvin G. , Hung L. S. , Nastasi M. , Thompson M. O. , Zheng L. R. 
Published: March 2011

ABSTRACTEnergy deposition and heat-flow determine the temperature distributions in pulsed-beam irradiated structures. In laser irradiated Si, transient conductance measurements indicated a liquid/solid interface velocity of 2.8 m/sec during crystallization in agreement with a heat flow model. With pulsed ionbeam annealing of metal-Si structures, melting starts at the interface; epitaxial NiSi2 layers have been formed. Ion-beammixing experiments on polycrystalline and epitaxial Au-Ag bilayers show that intermixing is more pronounced in the polycrystalline structures as is the case with thermal annealing. Superlattice structures are formed in the epitaxial structures.
Effect of Ion Irradiation on the Formation of Ni, Cr and Pt Silicide
Authors: Wielunski Leszek S. , Lien Chuen-Der , Liu Bai-Xin , Nicolet Marc-A. 
Published: March 2011

ABSTRACTThe influence of Xe+, As+ and Si+ irradiation on the Ni, Cr and Pt-silicide formed upon subsequent thermal annealings has been investigated. Helium MeV backscattering spectrometry and x-ray diffraction have been used to analyze the samples. The effect of silicon-metal interface contamination has been observed using an intentionally formed thin silicon oxide layer. The oxide layer was thick enough to prevent thermal silicide formation in unirradiated samples. In irradiated samples, the silicide forms thermally in spite of the presence of this oxide layer for Ni and Cr, but not for Pt. Similar results were obtained for Xe+, As+ and Si+ irradiations. We attribute this effect to ion mixing of the interfacial layer. The differences between results obtained with Ni, Cr and Pt are discussed. These results demonstrate that a low-dose irradiation can render the process of silicide formation upon thermal annealing tolerant to interfacial impurities. On the other hand, we also show that ion irradition can inhibit Pt and Ni silicide formation.
Structure and Properties of Single Crystal Al2O3 Implanted with Chromium and Zirconium
Authors: Mchargue C. J. , Naramoto H. , Appleton B. R. , White C. W. , Williams J. M. 
Published: March 2011

ABSTRACTSingle crystals of Al2O3 were implanted with chromium and zirconium to fluences of 1 × 1016 to 1 × 1017 ions cm−2. Rutherford backscattering-channeling studies showed the surface layers to be damaged but crystalline with the implanted ions randomly distributed. The microhardness and indentation fracture toughness were higher for the random solutions than for conventionally formed solid solutions. Changes in structure and properties caused by annealing in air at temperatures up to 1800°C were studied.
Metastable Percolation Phase Formation in Lif Implanted with Alkali Ions
Authors: Davenas J. , Thevenard P. , Dupuy C. 
Published: March 2011

ABSTRACTThe formation of a continuous metallic layer in the doped region of LiF crystals implanted at low temperature, has been explained by the formation of bridges between next neighbouring alkali ions of the lattice around-each implanted ion. For a critical concentration of implanted ions it is possible to show using statistical arguments that conducting chains are formed by the union of these links, according to a percolation mechanism. We show that the assumption of a distribution of isolated implanted ions at low temperature is justified by the observation of their precipitation when the crystal is warmed up to room temperature. The transformation of the metallic optical absorption into the colloidal band associated with precipitates of implanted ions is correlated with the transition from a conducting state to an insulating state of the implanted layer. We show that this evolution towards an equilibrium situation may be reversed by a reirradiation, which is used as an external perturbation and that the conducting state associated with dispersed implanted ions is then once again obtained.
Implantation into Covalent Polymeric Materials
Authors: Weber David C. , Brant Patrick , Carosella Carmine A. 
Published: March 2011

ABSTRACTIon implantation has been used to modify the organic semiconducting polymer, polyacetylene, (CH)x, and the semimetal, graphite, Cx. Implantation results in the formation of a unique polymer-fluorine interaction. This interaction leads to increased conductivity. The implantation also made the “doped” (CH)x resistant to the usual air oxidation which normally occurs with the conventionally doped polymers.