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Occurrence and Determination of Germanium in Coal Ash from Powerplants

Description: From Summary: "In this study the concentration of germanium was determined in numerous samples of coal and ash. A number of miscellaneous waste materials also were examined in the course of the investigation; the results are reported as a matter of general interest. The methods and equipment employed are discussed in detail."
Date: 1959
Creator: Corey, R. C.; Myers, J. W.; Schwartz, C. H.; Gibson, F. H. & Colbassani, P. J.
Partner: UNT Libraries Government Documents Department

The Occurrence of Germanium

Description: The following report discusses the possible sources of the uncommon element, germanium. It is the first in a series of reports to be prepared by the Geological Survey discussing rare and uncommon elements.
Date: February 1945
Creator: Fleischer, Michael & Harder, J. C.
Partner: UNT Libraries Government Documents Department

The Effect of Ashing Temperatures on the Volatility of Germanium in Lignite Samples

Description: Abstract: A study has been conducted to provide data on the loss of germanium from ashed lignite samples. The lignite samples, of known germanium content, were ashed at various temperatures as high as 1000 °C with varying rates of heating and varying amounts of surface area of the lignites. The results indicate that no germanium was volatilized during the various ignitions.
Date: September 1952
Creator: Tucker, Wendell P. & Waring, Claude L.
Partner: UNT Libraries Government Documents Department


Description: A bootstrapped-emitter-follower circuit that achieves an input impedance greater than 10/sup 7/ ohms with germanium transistors is described. The circuit is analyzed and compared with a single emitter follower and a super-alpha- connected emitter follower for input impedance characteristics. (auth)
Date: September 1, 1958
Creator: Baum, J.J.
Partner: UNT Libraries Government Documents Department


Description: A theoretical discussion is presented of the P-N junction theory and the junction transistor. A P-N juncion is where the two regions of a Ge crystal meet, one side of which is P-type, the other N-type. An NPN junction transistor consists of a single crystal, one end of which is N-type, a middle section which is P-type, and the composite end which is N-type. Silicon and Ge are the semiconductors commonly used. (W.L.H.)
Date: June 1, 1958
Creator: Leivo, W J
Partner: UNT Libraries Government Documents Department

Unique Rock-n-Roll Dynamic Appearance of a Ge-Si Ad-Dimer on Si(001)

Description: The authors carry out a comparative study of the energetic and dynamics of Si-Si, Ge-Ge, and Ge-Si ad-dimers on top of a dimer row in the Si(001) surface, using first-principles calculations. The dynamic appearance of a Ge-Si dimer is distinctively different from that of a Si-Si or Ge-Ge dimer, providing a unique way for its identification by scanning tunneling microscopy (STM). Its rocking motion, observed in STM, actually reflects a 180{degree} rotation of the dimer, involving a piecewise-rotation mechanism. The calculated energy barrier of 0.74 eV is in good agreement with the experimental value of 0.82 eV.
Date: July 24, 2000
Partner: UNT Libraries Government Documents Department

Picosecond Measurement of Interband Saturation, Intervalence Band Absorption, and Surface Recombination in Germanium

Description: The picosecond optical response of five thin germanium samples was measured following intense optical excitation using two variations of the excitation and probe technique. Seven-picosecond laser pulses of wavelength 1.054 um were used to measure the optical transmission of the samples for a variety of probe delays, excitation fluences, and sample temperatures. These parametric experiments were performed in an effort to determine if carrier cooling, carrier diffusion, or carrier recombination dominates the carrier dynamics immediately following excitation. The studies of a 5.7 um thick sample indicated that Auger recombination does not dominate the carrier dynamics, but that the carriers most likely cool immediately to within a few optical phonons of the lattice temperature. Lattice heating may also occur depending on excitation level. Neither cooling nor diffusion was ruled out as a major contributor to the transient optical response. A numerical analysis indicated that, although diffusion may be minimized in the thinner samples, the importance of surface recombination increases as the sample thickness decreases. The lattice temperature dependence of the optical transmission was found not to be in disagreement with the known temperature dependence of the low-density diffusion coefficient. Finally, new structure was observed in the data which is consistent with an increased intervalence band absorption at the highest excitation levels.
Date: August 1984
Creator: Perryman, Gary Paul
Partner: UNT Libraries

The Effect of Intervalence-Band Absorption, Auger Recombination, Surface Recombination, Diffusion and Carrier Cooling on the Picosecond Dynamics of Laser-Induced Plasmas in Germanium

Description: The picosecond optical response of germanium is investigated by performing excitation-probe experiments on a thin, intrinsic-germanium wafer maintained at 135 K. The results of three distinct experiments are reported: (1) the transmission of a single pulse is measured as a function of irradiance, (2) the probe transmission is measured at a fixed time after excitation as a function of the excitation energy, and (3) the transmission of a probe pulse is monitored as a function of time after excitation. These experiments employ 10-picosecond laser pulses at 1.06 um and Stokes-shifted pulses at 1.55-um.
Date: May 1983
Creator: Lindle, James Ryan
Partner: UNT Libraries

Ultra High-Rate Germanium (UHRGe) Modeling Status Report

Description: The Ultra-High Rate Germanium (UHRGe) project at Pacific Northwest National Laboratory (PNNL) is conducting research to develop a high-purity germanium (HPGe) detector that can provide both the high resolution typical of germanium and high signal throughput. Such detectors may be beneficial for a variety of potential applications ranging from safeguards measurements of used fuel to material detection and verification using active interrogation techniques. This report describes some of the initial radiation transport modeling efforts that have been conducted to help guide the design of the detector as well as a description of the process used to generate the source spectrum for the used fuel application evaluation.
Date: June 7, 2012
Creator: Warren, Glen A. & Rodriguez, Douglas C.
Partner: UNT Libraries Government Documents Department

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. The resulting net-impurity concentrations and the compensation ratios are precisely determined by the thermal neutron fluence and the [{sup 74}Ge]/[{sup 70}Ge] ratios of the starting Ge materials, respectively. This method also guarantees unprecedented doping uniformity. Using such samples the authors have conducted four types of electron (hole) transport studies probing the nature of (1) free carrier scattering by neutral impurities, (2) free carrier scattering by ionized impurities, (3) low temperature hopping conduction, and (4) free carrier transport in samples close to the metal-insulator transition.
Date: December 1994
Creator: Itoh, K.
Partner: UNT Libraries Government Documents Department

Opacity measurements: extending the range and filling in the gaps

Description: A series of experiments to explore Ge opacity at temperatures where the M-shell is almost filled will be discussed. Data are obtained at lower temperatures than previously explored and allow us to investigate the role of atomic structure calculations and their impact on opacity scalings. The experiment uses the Nova laser to irradiate a gold hohlraum within which a CH-tamped Ge sample is radiatively heated. A Nd backlight probes the sample 2 ns later to produce Ge spectral absorption features in the 1.2-1.5 keV energy range. Temperature is monitored by the use of an Al dopant and density is monitored by measuring the edge-on expansion of the sample. Temporal resolution of about 200 ps is obtained by using a short pulse backlight. Calculations in this photon energy region show significant changes in the spectral features.
Date: March 17, 1997
Creator: Back, C.A.; Perry, T.S.; Bach, D.R.; Wilson, G.; Iglesias, G.A.; Laden, O.L. et al.
Partner: UNT Libraries Government Documents Department

HPGe compton suppression using pulse shape analysis

Description: We present a new technique for High Purity Germanium (HPGe) Compton suppression using pulse shape analysis (PSA). The novel aspect of our approach involves a complete unfolding of the charge pulse shape into a discrete sum of component y-ray interactions. Using the energy and position information obtained from such an unfolding, an algorithm is then applied which favorably rejects Compton escape events. The advantage of the current PSA approach, as compared with other recent approaches, is the potential to reject not only single-site escape events, but also multiple site escape events. Here we discuss the details of our algorithm, and present experimental results from a real-time implementation on a 5 cm X 5 cm HPGe. An experimental comparison with a standard BGO suppresser is shown. We also discuss the possible improvements to the current PSA approach that could be obtained if the HPGe could be highly segmented on the outer contact.
Date: April 15, 1998
Creator: Schmid, G.J.; Beckedahl, D.; Blair, J.J. & Kammeraad, J.E.
Partner: UNT Libraries Government Documents Department

Optical properties of colloidal germanium nanocrystals

Description: Highly crystalline germanium (Ge) nanocrystals in the size range 2--10 nm were grown in inverse micelles and purified and size-separated by high pressure liquid chromatography with on-line optical and electrical diagnostics. The nanocrystals retain the diamond structure of bulk Ge down to at least 2.0 nm (containing about 150 Ge atoms). The background- and impurity-free extinction and photoluminescence (PL) spectra of these nanocrystals revealed rich structure which was interpreted in terms of the bandstructure of Ge shifted to higher energies by quantum confinement. The shifts ranged from {minus}0.1 eV to over 1 eV for the various transitions. PL in the range 350--700 nm was observed from nanocrystals 2--5 nm in size. The 2.0 nm nanocrystals yielded the most intense PL (at 420 nm) which is believed to be intrinsic and attributed to direct recombination at {Gamma}. Excitation at high energy (250 nm) populates most of the conduction bands resulting in competing recombination channels and the observed broad PL spectra.
Date: May 1, 2000
Partner: UNT Libraries Government Documents Department

Epitaxial growth simulation employing a combined molecular dynamics and Monte Carlo approach

Description: The epitaxial growth of Ge on Si(OO1) is simulated by employing a hybrid approach based on molecular dynamics to describe the initial kinetic behavior of deposited adatoms and Monte Carlo displacements to account for subsequent equilibration. This method is well suited to describe initial nucleation and growth. Stillinger-Weber potentials are employed to describe interatomic interactions.
Date: July 1, 1995
Creator: Grein, C.H.; Benedek, R. & Rubia, T. de la
Partner: UNT Libraries Government Documents Department

Novel SiGe Coherent Island Coarsening: Ostwald Ripening, Elastic Interactions, and Coalescence

Description: Real-time measurements of island coarsening during SiGe/Si (001) deposition reveal unusual kinetics. In particular, the mean island volume increases superlinearly with time, while the areal density of islands decreases at a faster-than-linear rate. Neither observation is consistent with standard considerations of Ostvvald ripening. We attribute our observed kinetics to the effect of elastic interactions in the densely growing island array. Island coalescence likely plays an important role as well.
Date: June 30, 1999
Creator: Chason, E.; Floro, J.A.; Freund, L.B.; Hwang, R.Q.; Lucadamo, G.A.; Sinclair, M. et al.
Partner: UNT Libraries Government Documents Department

High resolution XPS study of oxide layers grown on Ge substrates

Description: High resolution X-ray Photoelectron Spectroscopy (XPS) was used to analyze thin layers of germanium oxide grown on germanium substrates under various conditions. The results reveal the presence of high density of electron states located at the oxide/germanium interface that lead to the energy band bending. The surface of native oxide layers and that of thin oxide layer grown under dry oxygen correspond to GeO2 composition. Under Ar etching, lower oxidation states were revealed. Short in-situ heat treatment at T=400 degrees C under ultra high vacuum leads to the removal of the oxide layer. In addition, the analysis of the layer grown at T=380 degrees C under dry oxygen suggest that carbides form at the oxide/substrate interface.
Date: July 29, 2002
Creator: Tabet, N.; Faiz, M.; Hamdan, N.M. & Hussain, Z.
Partner: UNT Libraries Government Documents Department

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 thermochemistries of spirodigermetane, diallylgermetane and germacyclobutane have been explored via pulsed stirred-flow reactor (SFR) studies, showing remarkable differences in decomposition, depending on the substitution at the germanium atom. The second project investigates the thermochemical, photochemical, and catalytic additions of several digermanes to acetylenes. The first examples of thermo- and photochemical additions of Ge-Ge bonds to C{triple_bond}C are demonstrated. Mechanistic investigations are described and comparisons are made to analogous disilane addition reactions, previously studied in their group.
Date: December 12, 2003
Creator: Chubb, Andrew Michael
Partner: UNT Libraries Government Documents Department

FY08 Annual Report: Amorphous Semiconductors for Gamma Radiation Detection (ASGRAD)

Description: This is the annual report for an old project funded by NA22. The purpose of the project was to develop amorphous semiconductors for use as radiation detectors. The annual report contains information about the progress made in synthesizing, characterizing, and radiation response testing of these new materials.
Date: February 1, 2009
Creator: Johnson, Bradley R.; Riley, Brian J.; Crum, Jarrod V.; Ryan, Joseph V.; Sundaram, S. K.; McCloy, John S. et al.
Partner: UNT Libraries Government Documents Department

CryoFree Final Report

Description: CryoFree, a gamma-ray spectrometer, has been built and successfully tested. This instrument is based on a planar germanium semiconductor detector and is optimized for high-resolution spectroscopy in the range of a 30 keV to a few hundred keV to detect U and Pu. The spectrometer is cooled with a mechanical cryocooler that obviates the need for liquid cryogen. Furthermore, the instrument is battery powered. The combination of mechanical cooling and battery operation allows high-resolution spectroscopy in a highly-portable field instrument. A description of the instrument along with its performance is given.
Date: November 7, 2006
Creator: Burks, M
Partner: UNT Libraries Government Documents Department

MARS Flight Engineering Status

Description: The Multi-sensor Airborne Radiation Survey Flight Engineering project (MARS FE) has designed a high purity germanium (HPGe) crystal array for conducting a wide range of field measurements. In addition to the HPGe detector system, a platform-specific shock and vibration isolation system and environmental housing have been designed to support demonstration activities in a maritime environment on an Unmanned Surface Vehicle (USV). This report describes the status of the equipment as of the end of FY09.
Date: April 6, 2010
Creator: Fast, James E.; Dorow, Kevin E.; Morris, Scott J.; Thompson, Robert C. & Willett, Jesse A.
Partner: UNT Libraries Government Documents Department