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Some Compounds of Plutonium With Metalloid Elements

Description: From abstract: "Experimental methods of the type employed for alloy preparation in metallurgical research have been used in attempts to prepare compounds of plutonium with four different metalloid elements: phosphorous, arsenic, selenium, and tellurium. By means of their X-ray diffraction patterns the existences of six previously unknown compounds have been established, but the composition and crystal structures of only three of the compounds have been determined."
Date: 1955
Creator: Gorum, Alvin Eugene
Partner: UNT Libraries Government Documents Department

Stress relaxation of cellular silicone material: 1980

Description: Bendix Kansas City currently is evaluating the long-term (10 years) stress relaxation properties of cellular silicone materials at room temperature. The cellular structure is formed by using urea as a leachable filler. Both equilibrium (random copolymer) and condensation (block copolymer) type base polymers are included. Each material was compounded to yield two different densities for several thickness combinations. These density-thickness combinations then were compressed to nominal compressions of 20 and 40 percent with nine replicates at each condition. Five are tested regularly, two are 3 year controls, and two are 10 year controls.
Date: September 1, 1980
Creator: Schneider, J.W.
Partner: UNT Libraries Government Documents Department

Effect of Electronic Excitation on Thin Film Growth

Description: The effect of nanosecond pulsed laser excitation on surface diffusion during growth of Ge on Si(100) at 250 degrees C was studied. In Situ reflection high-energy electron diffraction (RHEED) was used to measure the surface diffusion coefficient while ex situ atomic force microscopy (AFM) was used to probe the structure and morphology of the grown quantum dots. The results show that laser excitation of the substrate increases the surface diffusion during growth of Ge on Si(100), changes the growth morphology, improves crystalline structure of the grown quantum dots, and decreases their size distribution. A purely electronic mechanism of enhanced surface diffusion of the deposited Ge is proposed. Ge quantum dots were grown on Si(100)-(2x1) by pulsed laser deposition at various substrate temperatures using a femtosecond Ti:sapphire laser. In-situ reflection high-energy electron diffraction and ex-situ atomic force microscopy were used to analyze the fim structure and morphology. The morphology of germanium islands on silicon was studied at differect coverages. The results show that femtosecond pulsed laser depositon reduces the minimum temperature for epitaxial growth of Ge quantum dots to ~280 degrees C, which is 120 degrees C lower then previously observed in nanosecond pulsed laser deposition and more than 200 degrees C lower than that reported for molecular beam epitaxy and chemical vapor deposition.
Date: January 31, 2011
Creator: Elsayed-Ali, Hani E.
Partner: UNT Libraries Government Documents Department

Selective Au-Si eutectic bonding for Si-based MEMS applications

Description: A novel method of fabricating three-dimensional silicon micro electromechanical systems (MEMS) is presented, using selectivity thin film deposited Au-Si eutectic bond pads. Utilizing this process, complicated structures such as microgrippers and microchannels are fabricated. Bond strengths are higher than the silicon fracture strength and the bond areas can be localized and aligned to the processed wafer. The process and the applications are described in this paper.
Date: May 22, 1995
Creator: Lee, A.; Lehew, S. & Yu, C.
Partner: UNT Libraries Government Documents Department

Effects of electronically neutral impurities on muonium in germanium

Description: Low-temperature measurements of muonium parameters in various germanium crystals have been performed. We have measured crystals with different levels of neutral impurities, with and without dislocations, and with different annealing histories. The most striking result is the apparent trapping of Mu by silicon impurities in germanium.
Date: April 1, 1983
Creator: Clawson, C.W.; Crowe, K.M.; Haller, E.E.; Rosenblum, S.S. & Brewer, J.H.
Partner: UNT Libraries Government Documents Department

Study of local atomic and electronic structure in glassy metallic alloys. Progress report, December 1, 1979-November 1, 1980

Description: During the first reporting period, March 1, 1979-December 1, 1979, small clusters such as Fe/sub 4/, Ni/sub 4/, Ni/sub 2/Fe/sub 2/ alone and containing the metalloid atoms P and B were investigated. The effect of P and B on the magnetic moment of the clusters was investigated and found to parallel the known experimental trend. Significant metal-metalloid bonding was found in all the clusters studied. During the present reporting period a detailed analysis of the bonding in these small clusters was carried out. As a result of this detailed analysis a very significant conclusion has been reached: there are preferential metal-metalloid interactions which are predicted on the basis of the calculations. Room temperature extended x-ray absorption fine structure (EXAFS) spectra above the K absorption edge of metal constituents in the following metal-metalloid and metal-metal glasses have been measured in the February and June 1980 runs at Stanford Synchrotron Radiation Laboratory: Fe/sub 1-x/B/sub x/, (FeNi)/sub 1-x/B/sub x/, Ni/sub 1-x/B/sub x/; Zr/sub 1-x/M/sub x/ (M- Fe, Co, Ni and Cu) and Nb/sub 1-x/Ni/sub x/.
Date: January 1, 1980
Creator: Messmer, R.P. & Wong, J.
Partner: UNT Libraries Government Documents Department

TEM studies of P/sup +/ implanted and subsequently laser annealed Si

Description: The present investigation is concerned with laser annealing of P/sup +/ implanted Si. The aim of the work was to study the crystallization behavior of damage structure occurring due to high dose rate implantation using transmission electron microscopy (TEM) as the method of examination.
Date: May 1, 1979
Creator: Sadana, D.K.; Wilson, M.C.; Booker, G.R. & Washburn, J.
Partner: UNT Libraries Government Documents Department

Model of amorphous-silicon-layer regrowth

Description: A new model which combines the heterogeneous nucleation and growth process for the mechanism of regrowth of amorphous silicon, in contact with a single crystal substrate, is presented. The model explains the effects of substrate orientation and impurity concentration on the kinetics of regrowth and also on the formation of twins during regrowth. The mechanism of redistribution of impurities and the formation of secondary defects during crystal regrowth are also discussed. A comparison of experimental results with the predictions of the model is also included.
Date: January 1, 1983
Creator: Ling, P.
Partner: UNT Libraries Government Documents Department

Many-body interactions in quasi-freestanding graphene

Description: The Landau-Fermi liquid picture for quasiparticles assumes that charge carriers are dressed by many-body interactions, forming one of the fundamental theories of solids. Whether this picture still holds for a semimetal such as graphene at the neutrality point, i.e., when the chemical potential coincides with the Dirac point energy, is one of the long-standing puzzles in this field. Here we present such a study in quasi-freestanding graphene by using high-resolution angle-resolved photoemission spectroscopy. We see the electron-electron and electron-phonon interactions go through substantial changes when the semimetallic regime is approached, including renormalizations due to strong electron-electron interactions with similarities to marginal Fermi liquid behavior. These findings set a new benchmark in our understanding of many-body physics in graphene and a variety of novel materials with Dirac fermions.
Date: June 3, 2011
Creator: Siegel, David; Park, Cheol-Hwan; Hwang, Choongyu; Deslippe, Jack; Fedorov, Alexei; Louie, Steven et al.
Partner: UNT Libraries Government Documents Department

SORPTION BEHAVIOR OF MONOSODIUM TITANATE AND AMORPHOUS PEROXOTITANATE MATERIALS UNDER WEAKLY ACIDIC CONDITIONS

Description: Inorganic, titanate-based sorbents are tested with respect to adsorption of a variety of sorbates under weakly acidic conditions (pH 3). Specifically, monosodium titanate (MST) and amorphous peroxotitanate (APT) sorption characteristics are initially probed through a screening process consisting of a pair of mixed metal solutions containing a total of 29 sorbates including alkali metals, alkaline earth metals, transition metals, metalloids and nonmetals. MST and APT sorption characteristics are further analyzed individually with chromium(III) and cadmium(II) using a batch method at ambient laboratory temperature, varying concentrations of the sorbents and sorbates and contact times. Maximum sorbate loadings are obtained from the respective adsorption isotherms.
Date: November 11, 2009
Creator: Hobbs, D.; Elvington, M. & Click, D.
Partner: UNT Libraries Government Documents Department

Enhancement of injection current at the metal-insulator interface

Description: Very deep traps may exist in amorphous insulators near a metal interface. When such traps are populated by photocarriers, large distortions in the electric field at the contact may result in carrier injection. A model of the time dependence and magnitude of the injection current is developed and compared with experimental results for the Si-SiO/sub 2/ interface and the metal-PET (polyethyleneterephthalate) interface.
Date: January 1, 1979
Creator: Hughes, R.C.
Partner: UNT Libraries Government Documents Department

Electronic properties of silicon grain boundaries

Description: Polycrystalline silicon is a clean and relatively simple prototype of electronic ceramics. The theory of the electrostatic barriers which form at silicon grain boundaries will be discussed. The use of experimental conductance and capacitance measurements to obtain the barrier height and energy density of grain boundary states will be illustrated.
Date: January 1, 1980
Creator: Pike, G.E. & Seager, C.H.
Partner: UNT Libraries Government Documents Department

Bulk band gaps in divalent hexaborides: A soft x-ray emission study

Description: Boron K-edge soft x-ray emission and absorption are used to address the fundamental question of whether divalent hexaborides are intrinsic semimetals or defect-doped bandgap insulators. These bulk sensitive measurements, complementary and consistent with surface-sensitive angle-resolved photoemission experiments, confirm the existence of a bulk band gap and the location of the chemical potential at the bottom of the conduction band.
Date: October 3, 2001
Creator: Denlinger, Jonathan D.; Gweon, Gey-Hong; Allen, James W.; Bianchi, Andrea D. & Fisk, Zachary
Partner: UNT Libraries Government Documents Department

Functional Analysis and Discovery of Microbial Genes Transforming Metallic and Organic Pollutants: Database and Experimental Tools

Description: Microbial functional genomics is faced with a burgeoning list of genes which are denoted as unknown or hypothetical for lack of any knowledge about their function. The majority of microbial genes encode enzymes. Enzymes are the catalysts of metabolism; catabolism, anabolism, stress responses, and many other cell functions. A major problem facing microbial functional genomics is proposed here to derive from the breadth of microbial metabolism, much of which remains undiscovered. The breadth of microbial metabolism has been surveyed by the PIs and represented according to reaction types on the University of Minnesota Biocatalysis/Biodegradation Database (UM-BBD): http://umbbd.ahc.umn.edu/search/FuncGrps.html The database depicts metabolism of 49 chemical functional groups, representing most of current knowledge. Twice that number of chemical groups are proposed here to be metabolized by microbes. Thus, at least 50% of the unique biochemical reactions catalyzed by microbes remain undiscovered. This further suggests that many unknown and hypothetical genes encode functions yet undiscovered. This gap will be partly filled by the current proposal. The UM-BBD will be greatly expanded as a resource for microbial functional genomics. Computational methods will be developed to predict microbial metabolism which is not yet discovered. Moreover, a concentrated effort to discover new microbial metabolism will be conducted. The research will focus on metabolism of direct interest to DOE, dealing with the transformation of metals, metalloids, organometallics and toxic organics. This is precisely the type of metabolism which has been characterized most poorly to date. Moreover, these studies will directly impact functional genomic analysis of DOE-relevant genomes.
Date: December 9, 2004
Creator: Wackett, Lawrence P. & Ellis, Lynda B.M.
Partner: UNT Libraries Government Documents Department

Damage nucleation in Si during ion irradiation

Description: Damage nucleation in single crystals of silicon during ion irradiation is investigated. Experimental results and mechanisms for damage nucleation during both room and liquid nitrogen temperature irradiation with different mass ions are discussed. It is shown that the accumulation of damage during room temperature irradiation depends on the rate of implantation. These dose rate effects are found to decrease in magnitude as the mass of the ions is increased. The significance of dose rate effects and their mass dependence on nucleation mechanisms is discussed.
Date: January 1, 1984
Creator: Holland, O.W.; Fathy, D. & Narayan, J.
Partner: UNT Libraries Government Documents Department

Study of short-range motion of atomic hydrogen in amorphous silicon by neutron reflectometry

Description: Preliminary results of neutron reflectometry (NR) measurements on rf sputter-deposited a-Si:H/a-Si:D bilayers indicate that this technique may be used to monitor H and D motions over distances of {approx} 10 to 200 {Angstrom} with a nominal resolution of 5--10 {Angstrom}. In studying rf sputter-deposited thin films containing a high density of microvoids annealed at 270 C, we found that the hydrogen diffused a distance of only {approx} 100 {Angstrom}. Further annealing at 270 and 280 C produced no additional motion. This result is consistent with a model of this system in which the hydrogen is trapped in microvoids after moving a relatively short distance.
Date: May 1, 1992
Creator: Dozier, W.D. (Argonne National Lab., IL (United States)); Herwig, K.W. (Missouri Univ., Columbia, MO (United States). Research Reactor Facility); Shinar, R. (Iowa State Univ. of Science and Technology, Ames, IA (United States). Microelectronics Research Center); Jia, H. & Shinar, J. (Ames Lab., IA (United States))
Partner: UNT Libraries Government Documents Department

Hydrogen in amorphous silicon

Description: The structural aspects of amorphous silicon and the role of hydrogen in this structure are reviewed with emphasis on ion implantation studies. In amorphous silicon produced by Si ion implantation of crystalline silicon, the material reconstructs into a metastable amorphous structure which has optical and electrical properties qualitatively similar to the corresponding properties in high-purity evaporated amorphous silicon. Hydrogen studies further indicate that these structures will accomodate less than or equal to 5 at.% hydrogen and this hydrogen is bonded predominantly in a monohydride (SiH/sub 1/) site. Larger hydrogen concentrations than this can be achieved under certain conditions, but the excess hydrogen may be attributed to defects and voids in the material. Similarly, glow discharge or sputter deposited amorphous silicon has more desirable electrical and optical properties when the material is prepared with low hydrogen concentration and monohydride bonding. Results of structural studies and hydrogen incorporation in amorphous silicon were discussed relative to the different models proposed for amorphous silicon.
Date: January 1, 1980
Creator: Peercy, P. S.
Partner: UNT Libraries Government Documents Department

Structure and stability of microvoids in A-Si:H

Description: Microvoids appear to be universally present in a-Si:H as demonstrated by small angle X-ray scattering including the presence of microvoids in device quality glow discharge a-Si:H. We have studied the structural properties of these microvoids with molecular dynamics simulations. Using molecular dynamics simulations with classical potentials, we have created microvoids by removing Si and H atoms from a computer generated a-Si:H network. The internal surfaces of the microvoids were passivated with additional H atoms and the microvoids were fully relaxed. Microvoids over a limited range of sizes (5--90 missing atoms) were examined. We obtained a relaxed microvoid structure with no dangling bonds for a microvoid with 17 missing atoms, whereas other sizes examined produced less relaxed models with short H-H distances at the microvoid surface. The strains near the microvoid surface are described. The microvoid model was stable to local excitations on weak bonds in the vicinity of the microvoid.
Date: January 1, 1993
Creator: Biswas, R. (Iowa State Univ. of Science and Technology, Ames, IA (United States). Microelectronics Research Center) & Kwon, I. (Los Alamos National Lab., NM (United States))
Partner: UNT Libraries Government Documents Department

Semiconductor chip processing. Final report

Description: The processes necessary to assemble metal-oxide semiconductor devices in hermetic ceramic packages were developed. The assembly techniques developed were gold-silicon die attachment, 25.4-..mu..m aluminum wire interconnection, and gold-tin cover attachment.
Date: July 1, 1980
Creator: Grimm, A.V.
Partner: UNT Libraries Government Documents Department

Magnetic decoupling in sputtered Fe/Si superlattices and multilayers

Description: A series of sputtered Fe/Si superlattices was grown to study the magnetic coupling between ferromagnetic Fe layers (30[Angstrom] thick) for Si spacer-layer thicknesses (t[sub Si]) between 10 and 40[Angstrom]. The material is ferromagnetically coupled for t[sub Si]<13[Angstrom] and antiferromagneticly coupled for 13[Angstrom]<t[sub Si]<17[Angstrom]. For t[sub Si]>17[Angstrom] the magnetic Fe layers are uncoupled. X-ray analysis indicates that the system is well layered, but that the crystal structure remains coherent only for t[sub Si]<17[Angstrom]. These results, along with our Moessbauer investigation, strongly suggest that the Si layer is crystalline for t[sub Si]<17[Angstrom], and is iron silicide in nature. For thicker spacers, Si becomes amorphous. We propose a model of the layering that is consistent with the known properties of Fe-silicide.
Date: September 1, 1992
Creator: Fullerton, E.E.; Mattson, J.E.; Lee, S.R.; Sowers, C.H.; Huang, Y.Y.; Felcher, G. et al.
Partner: UNT Libraries Government Documents Department

Characterization of on-chip polycrystalline silicon photoconductors

Description: We report experimental and modeling studies of on-ship photoconductor pulse generation and sampling. Specifically, we discuss (a) the effect of ion-beam damage on carrier lifetime and sampling-aperture time, (b) the circuit limits to pulse risetime, and (c) the room-temperature stability of ion-beam-damaged sampling gates.
Date: January 1, 1986
Creator: Fitzpatrick, D.K.; Bowman, D.R. & Hammond, R.B.
Partner: UNT Libraries Government Documents Department