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A search for particle dark matter using cryogenic germanium and silicon detectors in the one- and two- tower runs of CDMS-II at Soudan

Description: Images of the Bullet Cluster of galaxies in visible light, X-rays, and through gravitational lensing confirm that most of the matter in the universe is not composed of any known form of matter. The combined evidence from the dynamics of galaxies and clusters of galaxies, the cosmic microwave background, big bang nucleosynthesis, and other observations indicates that 80% of the universe's matter is dark, nearly collisionless, and cold. The identify of the dar, matter remains unknown, but weakly … more
Date: April 1, 2008
Creator: Ogburn, Reuben Walter, IV
Partner: UNT Libraries Government Documents Department
open access

Transient and temperature-dependent phenomena in Ge:Be and Ge:Zn far infrared photoconductors

Description: An experimental study of the transient and temperature-dependent behavior of Ge:Be and Ge:Zn photoconductors has been performed under the low background photon flux conditions (p dot approx. = 10/sup 8/ photons/second) typical of astronomy and astrophysics applications. The responsivity of Ge:Be and Ge:Zn detectors is strongly temperature-dependent in closely compensated material, and the effect of compensation on free carrier lifetime in Ge:Be has been measured using the photo-Hall effect tech… more
Date: November 1985
Creator: Haegel, Nancy Marie
Partner: UNT Libraries Government Documents Department
open access

Gas phase thermochemistry of organogermanium compounds

Description: A variety of silyl- and alkyl-germylene precursors have been synthesized and subsequently pyrolyzed in the gas phase. Arrhenius parameters were obtained employing a pulsed-stirred flow reactor for these unimolecular decompositions. These precursors are divided into two major categories by mechanism of germylene extrusion: {alpha}-elimination precursors and germylacetylenes. The extrusion of germylenes from germylacetylene precursors is of primary interest. A mechanism is proposed employing a ge… more
Date: December 7, 1993
Creator: Engel, J. P.
Partner: UNT Libraries Government Documents Department
open access

Uniaxially stressed Ge:Ga and Ge:Be

Description: The application of a large uniaxial stress to p-type Ge single crystals changes the character of both the valence band and the energy levels associated with the acceptors. Changes include the splitting of the fourfold degeneracy of the valence band top and the reduction of the ionization energy of shallow acceptors. In order to study the effect of uniaxial stress on transport properties of photoexcited holes, a variable temperature photo-Hall effect system was built in which stressed Ge:Ga and … more
Date: December 1, 1992
Creator: Dubon, O. D. Jr.
Partner: UNT Libraries Government Documents Department
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Development and Performance of Detectors for the Cryogenic Dark Matter Search Experiment with an Increased Sensitivity Based on a Maximum Likelihood Analysis of Beta Contamination

Description: The Cryogenic Dark Matter Search (CDMS) uses cryogenically-cooled detectors made of germanium and silicon in an attempt to detect dark matter in the form of Weakly-Interacting Massive Particles (WIMPs). The expected interaction rate of these particles is on the order of 1/kg/day, far below the 200/kg/day expected rate of background interactions after passive shielding and an active cosmic ray muon veto. Our detectors are instrumented to make a simultaneous measurement of both the ionization ene… more
Date: January 1, 2004
Creator: Driscoll, Donald D. & U., /Case Western Reserve
Partner: UNT Libraries Government Documents Department
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Structural/magnetic phase transitions and superconductivity in Ba(Fe<sub>1-x</sub>TM<sub>x</sub>)<sub>2</sub>As<sub>2</sub> (TM=Co, Ni, Cu, Co/Cu, Rh and Pd) single crystals

Description: Since its discovery in 1911, superconductivity has been one of the most actively studied fields in condensed matter physics and has attracted immense experimental and theoretical effort. At this point in time, with more and more superconductors discovered in elements, alloys, intermetallic compounds and oxides, it is becoming clear that superconductivity is actually not so rare in nature. Almost half of the elements in the periodic table and hundreds of compounds have been found to be supercond… more
Date: January 1, 2009
Creator: Ni, Ni
Partner: UNT Libraries Government Documents Department
open access

Preparation, crystallography, magnetic and magnetothermal properties of Ce5SiGe4-x alloys

Description: An investigation of the crystal structure and the phase relationships in the Ce{sub 5}Si{sub 4-x}Ge{sub x} system has been carried out. The crystal structures of the single phase intermetallics were characterized using X-ray powder diffraction and subsequent refinement employing the Rietveld analysis technique was performed. The intermetallic system was found to crystallize in three distinct crystal structures. The Ce{sub 5}Si{sub 4}-based solid solution extends from x = 0 to x = 2.15 and it wa… more
Date: May 1, 2005
Creator: Vijayaraghavan, Rangarajan
Partner: UNT Libraries Government Documents Department
open access

Organogermanium Chemistry: Germacyclobutanes and digermane Additions to Acetylenes

Description: This dissertation comprises two main research projects. The first project, presented in Chapter 1, involves the synthesis and thermochemistry of germacyclobutanes (germetanes). Four new germetanes (spirodigermetane, diallylgermetane, dichlorogermetane, and germacyclobutane) have been synthesized using a modified di-Grignard synthesis. Diallylgermetane is shown to be a useful starting material for obtaining other germetanes, particularly the parent germetane, germacyclobutane. The gas-phase ther… more
Date: December 12, 2003
Creator: Chubb, Andrew Michael
Partner: UNT Libraries Government Documents Department
open access

Liquid phase epitaxial growth and characterization of germanium far infrared blocked impurity band detectors

Description: Germanium Blocked Impurity Band (BIB) detectors require a high purity blocking layer (&lt; 10{sup 13} cm{sup -3}) approximately 1 mm thick grown on a heavily doped active layer ({approx} 10{sup 16} cm{sup -3}) approximately 20 mm thick. Epilayers were grown using liquid phase epitaxy (LPE) of germanium out of lead solution. The effects of the crystallographic orientation of the germanium substrate on LPE growth modes were explored. Growth was studied on substrates oriented by Laue x-ray diffrac… more
Date: May 12, 2001
Creator: Bandaru, Jordana
Partner: UNT Libraries Government Documents Department
open access

Magnetic, Caloric and Crystallographic Properties of Dy5(SixGe1-x)4 Alloys

Description: Polycrystals of the intermetallic compound of the Dy{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} system, where x = 0, 0.25, 0.5, 0.625, 0.675, 0.725, 0.75, 0.775, 0.825, 0.875, and 1, have been prepared by electric-arc-melting on water-cooled copper hearth in an argon atmosphere. A study of phase relationships and crystallography in the pseudobinary system Dy{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} using X-ray powder diffraction data and optical metallography was completed. It revealed that silicides in th… more
Date: July 19, 2002
Creator: Ivchenko, Vitaliy Vladislavovich
Partner: UNT Libraries Government Documents Department
open access

High Growth Rate Deposition of Hydrogenated Amorphous Silicon-Germanium Films and Devices Using ECR-PECVD

Description: Hydrogenated amorphous silicon germanium films (a-SiGe:H) and devices have been extensively studied because of the tunable band gap for matching the solar spectrum and mature the fabrication techniques. a-SiGe:H thin film solar cells have great potential for commercial manufacture because of very low cost and adaptability to large-scale manufacturing. Although it has been demonstrated that a-SiGe:H thin films and devices with good quality can be produced successfully, some issues regarding grow… more
Date: May 31, 2002
Creator: Liu, Yong
Partner: UNT Libraries Government Documents Department
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Investigation of the Wett-Ability of Various Pure Metals and Alloys on Beryllium

Description: Thesis submitted to University of Tennessee, Knoxville. Activities in a program to determine the wetting behavior of pure metals such as Au, Ag, Ge, Al, and Cu on solid Be are reported. Results of similar investigations of binary alloys such as Be--Ti, Be-Zr, and Be--Pd are also included. The contact angles of the molten metals on Be as a function of temperature, exposure time, and atmosphere were measured. The solid-liquid interfacial reactions occurring as a function of test temperature and a… more
Date: June 13, 1963
Creator: Gilliland, R. G.
Partner: UNT Libraries Government Documents Department
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Spin distribution in preequilibrium reactions for 48Ti + n.

Description: Cross section measurements were made of prompt {gamma}-ray production as a function of incident neutron energy on a {sup 48}Ti sample. Partial {gamma}-ray cross sections for transitions in {sup 45-48}Ti, {sup 44-48}Sc, and {sup 42-45}Ca have been determined. Energetic neutrons were delivered by the Los Alamos National Laboratory spallation neutron source located at the LANSCE/WNR facility. The prompt-reaction {gamma} rays were detected with the large-scale Compton-suppressed germanium array for… more
Date: April 6, 2005
Creator: Dashdorj, D
Partner: UNT Libraries Government Documents Department
open access

Extending the Sensitivity to the Detection of WIMP Dark Matter with an Improved Understanding of the Limiting Neutron Backgrounds

Description: The Cryogenic Dark Matter Search (CDMS) uses position-sensitive Germanium and Silicon crystals in the direct detection of Weakly Interacting Massive Particles (WIMPs) believed to constitute most of the dark matter in the Universe. WIMP interactions with matter being rare, identifying and eliminating known backgrounds is critical for detection. Event-by-event discrimination by the detectors rejects the predominant gamma and beta backgrounds while Monte Carlo simulations help estimate, and subtra… more
Date: January 1, 2005
Creator: Kamat, Sharmila & U., /Case Western Reserve
Partner: UNT Libraries Government Documents Department
open access

THE CARRIER-RECOMBINATION BEHAVIOR AND ANNEALING PROPERTIES OF RADIATION- INDUCED RECOMBINATION CENTERS IN GERMANIUM

Description: Carrier recombination and annealing of radioinduced recombination centers were investigated for both n- and ptype Ge. The experimental results are explained by a model in which recombination occurs at 0.36 ev above the valence band in gamma -irradiated, n-type Ge; the position of this level is shifted slightly downward for neutron-irradiated Ge. Trapping levels occur in As-doped Ge (at 0.17 ev above the valence band) which are not present in Sb-doped Ge. For p-type Ge, an energy level present i… more
Date: June 1, 1961
Creator: Curtis, O.L. Jr. & Crawford, J.H. Jr.
Partner: UNT Libraries Government Documents Department
open access

EMISSION SPECTRA OF ELECTRON IRRADIATED METAL FOILS

Description: Thesis submitted to Univ. of Tennessee by L. C. Emerson. An experimental investigation of the visible and ultraviolet light emitted when a charged particle moves across a boundary between two media with different dielectric properties was carried out. The spectral distributions of the light from evaporated foils of copper, germanium, silver, tin, and antimony bombarded by a 1.5-microamp beam of electrons were measured as a function of electron energy between 25 and 100 kev. The analysis was car… more
Date: August 1, 1963
Creator: Emerson, L. C.; Arakawa, E. T.; Ritchie, R. H. & Birkhoff, R. D.
Partner: UNT Libraries Government Documents Department
open access

Low temperature carrier transport properties in isotopically controlled germanium

Description: Investigations of electronic and optical properties of semiconductors often require specimens with extremely homogeneous dopant distributions and precisely controlled net-carrier concentrations and compensation ratios. The previous difficulties in fabricating such samples are overcome as reported in this thesis by growing high-purity Ge single crystals of controlled {sup 75}Ge and {sup 70}Ge isotopic compositions, and doping these crystals by the neutron transmutation doping (NTD) technique. Th… more
Date: December 1994
Creator: Itoh, K.
Partner: UNT Libraries Government Documents Department
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Advanced far infrared detector and double donor studies in Ge

Description: This has application to astronomy and astrophysics. Selenium in Ge has been studied with a doping technique which limits complex formation. Only one ionization level has been found to correspond to selenium, which presumably occupies a substitutional site. This level is extremely unstable and its concentration decreases after annealing at 400C. Future work is planned to anneal the fast neutron damage before much selenium has formed in the {sup 74/76}Ge samples. It is expected that the observed … more
Date: December 1, 1994
Creator: Olsen, C.S.
Partner: UNT Libraries Government Documents Department
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Effect of uniaxial stress on gallium, beryllium, and copper-doped germanium hole population inversion lasers

Description: The effects of stress on germanium lasers doped with single, double, and triple acceptors have been investigated. The results can be explained quantitatively with theoretical calculations and can be attributed to specific changes in the energy levels of acceptors in germanium under stress. In contrast to previous measurements, gallium-doped Ge crystals show a decrease in lasing upon uniaxial stress. The decrease seen here is attributed to the decrease in heavy hole effective mass upon applicati… more
Date: May 1998
Creator: Chamberlin, D. R.
Partner: UNT Libraries Government Documents Department
open access

Electronic processes in uniaxially stressed p-type germanium

Description: Effect of uniaxial stress on acceptor-related electronic processes in Ge single crystals doped with Ga, Be, and Cu were studied by Hall and photo-Hall effect measurements in conjunction with infrared spectroscopy. Stress dependence of hole lifetime in p-type Ge single crystals is used as a test for competing models of non-radiative capture of holes by acceptors. Photo-Hall effect shows that hole lifetime in Ga- and Be-doped Ge increases by over one order of magnitude with uniaxial stress at liq… more
Date: February 1, 1996
Creator: Dubon, O.D. Jr.
Partner: UNT Libraries Government Documents Department
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Synthesis and Gas Phase Thermochemistry of Germanium-Containing Compounds

Description: The driving force behind much of the work in this dissertation was to gain further understanding of the unique olefin to carbene isomerization observed in the thermolysis of 1,1-dimethyl-2-methylenesilacyclobutane by finding new examples of it in other silicon and germanium compounds. This lead to the examination of a novel phenylmethylenesilacyclobut-2-ene, which did not undergo olefin to carbene rearrangement. A synthetic route to methylenegermacyclobutanes was developed, but the methyleneger… more
Date: December 31, 2002
Creator: Classen, Nathan Robert
Partner: UNT Libraries Government Documents Department
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