Sample records for gaas gypsum plaster

  1. FGD gypsum's place in American agriculture

    SciTech Connect (OSTI)

    Haynes, C. [US Department of Agriculture (United States). Agricultural Research Service

    2007-07-01T23:59:59.000Z

    Surface cracks and soil clumps form when saline-sodic, high-clay soil dries out. Treatment with FGD gypsum and irrigation water flowing into these cracks leaches salts until the aggregates swell and the cracks close up. The article describes research projects to develop agricultural uses of FGD gypsum from coal-fired power plants that have been conducted by university researchers and USDA-Agricultural Research Service scientists.

  2. Automatic 3D modeling of palatal plaster casts Marco Andreetto

    E-Print Network [OSTI]

    Abu-Mostafa, Yaser S.

    duplicated by 3D printers. A second application where 3D models of palatal casts could also be usefulAutomatic 3D modeling of palatal plaster casts Marco Andreetto Dept. of Information Engineer corte@dei.unipd.it Abstract This work introduces a procedure for automatic 3D model- ing and discusses

  3. What You Need to Know About Gypsum

    E-Print Network [OSTI]

    Balser, Teri C.

    TestCa(ppm) Arlington Ashland Lancaster Spooner 0 100 200 300 400 500 600 700 SoilTestMg(ppm) Arlington Ashland applied (t/a) 5.8 6.0 6.2 6.4 6.6 6.8 7.0 SoilpH Arlington Ashland Lancaster Spooner 5.8 6.0 6.2 6.4 6.6 6.8 7.0 7.2 SoilpH Arlington Ashland Lancaster Spooner 0 1 4 16 Effect of gypsum additions on soil p

  4. Crack coalescence in molded gypsum and Carrara marble

    E-Print Network [OSTI]

    Wong, Ngai Yuen

    2008-01-01T23:59:59.000Z

    This thesis investigates the fracturing and coalescence behavior in prismatic laboratory molded gypsum and Carrara marble specimens, which consist of either one or two preexisting open flaws, under uniaxial compression. ...

  5. Fate of Mercury in Synthetic Gypsum Used for Wallboard Production

    SciTech Connect (OSTI)

    Jessica Marshall Sanderson

    2006-06-01T23:59:59.000Z

    This report presents and discusses results from Task 5 of the study ''Fate of Mercury in Synthetic Gypsum Used for Wallboard Production,'' performed at a full-scale commercial wallboard plant. Synthetic gypsum produced by wet flue gas desulfurization (FGD) systems on coal-fired power plants is commonly used in the manufacture of wallboard. The FGD process is used to control the sulfur dioxide emissions which would result in acid rain if not controlled. This practice has long benefited the environment by recycling the FGD gypsum byproduct, which is becoming available in increasing quantities, decreasing the need to landfill this material, and increasing the sustainable design of the wallboard product. However, new concerns have arisen as recent mercury control strategies developed for power plants involve the capture of mercury in FGD systems. The objective of this study is to determine whether any mercury is released into the atmosphere when the synthetic gypsum material is used as a feedstock for wallboard production. The project is being co-funded by the U.S. DOE National Energy Technology Laboratory (Cooperative Agreement DE-FC26-04NT42080), USG Corporation, and EPRI. USG Corporation is the prime contractor, and URS Group is a subcontractor. The project scope includes five discrete tasks, each conducted at various USG wallboard plants using synthetic gypsum from different FGD systems. The five tasks were to include (1) a baseline test, then variations representing differing power plant (2) emissions control configurations, (3) treatment of fine gypsum particles, (4) coal types, and (5) FGD reagent types. However, Task 5, which was to evaluate gypsum produced from an alternate FGD reagent, could not be conducted as planned. Instead, Task 5 was conducted at conditions similar to a previous task, Task 3, although with gypsum from an alternate FGD system. In this project, process stacks in the wallboard plant have been sampled using the Ontario Hydro method. The stack locations sampled for each task include a dryer for the wet gypsum as it enters the plant and a gypsum calciner. The stack of the dryer for the wet wallboard product was also tested as part of this task, and was tested as part of Tasks 1 and 4. Also at each site, in-stream process samples were collected and analyzed for mercury concentration before and after each significant step in wallboard production. The Ontario Hydro results, process sample mercury concentration data, and process data were used to construct mercury mass balances across the wallboard plants. Task 5 was conducted at a wallboard plant processing synthetic gypsum from a power plant that fires Eastern bituminous coal. The power plant is equipped with a selective catalytic reduction (SCR) system for NOX emissions control, but the SCR was bypassed during the time period the gypsum tested was produced. The power plant has a single-loop, open spray tower, limestone reagent FGD system, with forced oxidation conducted in a reaction tank integral with the FGD absorber. The FGD system has gypsum fines blow down as part of the dewatering step. Gypsum fines blow down is believed to be an important variable that impacts the amount of mercury in the gypsum byproduct and possibly its stability during the wallboard process. The results of the Task 5 stack testing, as measured by the Ontario Hydro method, detected that an average of 51% of the incoming mercury in the FGD gypsum was emitted during wallboard production. These losses were distributed as 2% or less each across the wet gypsum dryer and product wallboard dryer, and about 50% across the gypsum calciner. Emissions were similar to what Task 3 results showed, on both a percentage and a mass basis, for gypsum produced by a power plant firing bituminous coal and also having gypsum fines blow down as part of the FGD dewatering scheme. As was seen in the Task 1 through 4 results, most of the mercury detected in the stack testing on the wet gypsum dryer and kettle calciner was in the form of elemental mercury. In the wallboard dryer kiln, a more signific

  6. Fate of Mercury in Synthetic Gypsum Used for Wallboard Production

    SciTech Connect (OSTI)

    Jessica Sanderson

    2007-12-31T23:59:59.000Z

    This report presents and discusses results from the project 'Fate of Mercury in Synthetic Gypsum Used for Wallboard Production', performed at five different full-scale commercial wallboard plants. Synthetic gypsum produced by wet flue gas desulfurization (FGD) systems on coal-fired power plants is commonly used in the manufacture of wallboard. This practice has long benefited the environment by recycling the FGD gypsum byproduct, which is becoming available in increasing quantities, decreasing the need to landfill this material, and increasing the sustainable design of the wallboard product. However, new concerns have arisen as recent mercury control strategies involve the capture of mercury in FGD systems. The objective of this study has been to determine whether any mercury is released into the atmosphere at wallboard manufacturing plants when the synthetic gypsum material is used as a feedstock for wallboard production. The project has been co-funded by the U.S. DOE National Energy Technology Laboratory (Cooperative Agreement DE-FC26-04NT42080), USG Corporation, and EPRI. USG Corporation is the prime contractor, and URS Group is a subcontractor. The project scope included seven discrete tasks, each including a test conducted at various USG wallboard plants using synthetic gypsum from different wet FGD systems. The project was originally composed of five tasks, which were to include (1) a base-case test, then variations representing differing power plant: (2) emissions control configurations, (3) treatment of fine gypsum particles, (4) coal types, and (5) FGD reagent types. However, Task 5,could not be conducted as planned and instead was conducted at conditions similar to Task 3. Subsequently an opportunity arose to test gypsum produced from the Task 5 FGD system, but with an additive expected to impact the stability of mercury, so Task 6 was added to the project. Finally, Task 7 was added to evaluate synthetic gypsum produced at a power plant from an additional coal type. In the project, process stacks in the wallboard plant were sampled using the Ontario Hydro method. In every task, the stack locations sampled included a gypsum dryer and a gypsum calciner. In Tasks 1 and 4 through 7, the stack of the dryer for the wet wallboard product was also tested. Also at each site, in-stream process samples were collected and analyzed for mercury concentration before and after each significant step in wallboard production. These results and process data were used to construct mercury mass balances across the wallboard plants. The results from the project showed a wide range of percentage mercury losses from the synthetic gypsum feedstocks as measured by the Ontario Hydro method at the process stacks, ranging from 2% to 55% of the mercury in the gypsum feedstock. For the tasks exceeding 10% mercury loss across the wallboard plant, most of the loss occurred across the gypsum calciner. When total wallboard emissions remained below 10%, the primary emission location varied with a much less pronounced difference in emission between the gypsum dryer, calciner and board dryer. For all seven tasks, the majority of the mercury emissions were measured to be in the elemental form (Hg{sup 0}). Overall, the measured mercury loss mass rates ranged from 0.01 to 0.17 grams of mercury per dry ton of synthetic gypsum processed, or 0.01 to 0.4 pounds of mercury released per million square feet of wallboard produced from synthetic gypsum. The Coal Combustion Product Production and Use Survey from the American Coal Ash Association (ACAA) indicate that 7,579,187 short tons of synthetic gypsum were used for wallboard production in 2006. Extrapolating the results of this study to the ACAA industry usage rate, we estimate that mercury releases from wallboard production plants in 2006 ranged between 150 to 3000 pounds for the entire U.S. wallboard industry. With only seven sets of wallboard plant measurements, it is difficult to draw firm conclusions about what variables impact the mercury loss percentages across the wallboard plants. One significant o

  7. Gypsum and Polyacrylamide Soil Amendments Used With High Sodium Wastewater

    E-Print Network [OSTI]

    Gardiner, Duane

    and sodium. Two soil amendments were applied to plots furrowirrigated with wastewater. The amendments were gypsum (11 Mg ha-1), and PAM added to irrigation water at rates of 25 mg L-1 PAM applications were made during every irrigation and during every second...

  8. Fate of Mercury in Synthetic Gypsum Used for Wallboard Production

    SciTech Connect (OSTI)

    Jessica Sanderson; Gary M. Blythe; Mandi Richardson

    2006-12-01T23:59:59.000Z

    This report presents and discusses results from Task 6 of the study 'Fate of Mercury in Synthetic Gypsum Used for Wallboard Production,' performed at a full-scale commercial wallboard plant. Synthetic gypsum produced by wet flue gas desulfurization (FGD) systems on coal-fired power plants is commonly used in the manufacture of wallboard. This practice has long benefited the environment by recycling the FGD gypsum byproduct, which is becoming available in increasing quantities, decreasing the need to landfill this material, and increasing the sustainable design of the wallboard product. However, new concerns have arisen as recent mercury control strategies involve the capture of mercury in FGD systems. The objective of this study is to determine whether any mercury is released into the atmosphere when the synthetic gypsum material is used as a feedstock for wallboard production. The project is being co-funded by the U.S. DOE National Energy Technology Laboratory (Cooperative Agreement DE-FC26-04NT42080), USG Corporation, and EPRI. USG Corporation is the prime contractor, and URS Group is a subcontractor. The project scope now includes six discrete tasks, each conducted at various USG wallboard plants using synthetic gypsum from different FGD systems. The project was originally composed of five tasks, which were to include (1) a baseline test, then variations representing differing power plant: (2) emissions control configurations, (3) treatment of fine gypsum particles, (4) coal types, and (5) FGD reagent types. However, Task 5, which was to include testing with an alternate FGD reagent, could not be conducted as planned. Instead, Task 5 was conducted at conditions similar to Task 3, although with gypsum from an alternate FGD system. Subsequent to conducting Task 5 under these revised conditions, an opportunity arose to test gypsum produced at the same FGD system, but with an additive (Degussa Corporation's TMT-15) being used in the FGD system. TMT-15 was expected to impact the stability of mercury in synthetic gypsum used to produce wallboard, so Task 6 was added to the project to test this theory. In this project, process stacks in the wallboard plant have been sampled using the Ontario Hydro method. For every task, the stack locations sampled have included a dryer for the wet gypsum as it enters the plant and a gypsum calciner. For Tasks 1, 4, 5 and 6, the stack of the dryer for the wet wallboard product was also tested. Also at each site, in-stream process samples were collected and analyzed for mercury concentration before and after each significant step in wallboard production. The Ontario Hydro results, process sample mercury concentration data, and process data were used to construct mercury mass balances across the wallboard plants. Task 6 was conducted at a wallboard plant processing synthetic gypsum from a power plant that fires Eastern bituminous coal. The power plant has a single-loop, open spray tower limestone forced oxidation FGD system, with the forced oxidation conducted in the reaction tank integral with the FGD absorber. The FGD system has gypsum fines blow down as part of the dewatering step. The power plant is equipped with a selective catalytic reduction (SCR) system for NOX emissions control, and the SCR was in service during the time period the gypsum tested was produced. Also, as mentioned above, Degussa additive TMT-15 was being added to the FGD system when this gypsum was produced. The results of the Task 6 stack testing, as measured by the Ontario Hydro method, detected that an average of 55% of the incoming mercury was emitted during wallboard production. These losses were distributed as about 4% across the dryer mill, 6% across the board dryer kiln, and 45% across the kettle calciner. Emissions were similar to what Task 5 results showed on a percentage basis, but about 30% lower on a mass basis. The same power plant FGD system produced the synthetic gypsum used in Task 5 (with no use of TMT-15) and in Task 6 (with TMT-15 added to the FGD system). The lower emissions on a mass basis appeared

  9. Is Gypsum Application Beneficial to Soil? Francisco J. Arriaga

    E-Print Network [OSTI]

    Balser, Teri C.

    (A2809-Laboski & Peters, 2012) #12;Liming Value Material Neutralizing agent CaCO3 equivalent (pure material) ---- % ---- Dolomitic limestone CaCO3·MgCO3 110-118 Calcitic limestone CaCO3 100 Wood ash K2CO3, CaCO3, MgCO3 20-90 Gypsum none 0 (A3588-Management of Wisconsin Soils) #12;Sulfur in Wisconsin Soils

  10. EFFECT OF GYPSUM ON AVAILABLE PHOSPHORUS EVALUATED BY MEHLICH-1, ION EXCHANGE RESIN, AND Pi-PAPER IN A BRAZILIAN TROPICAL OXISOL

    E-Print Network [OSTI]

    Silva, Rodrigo Coqui da; Chien, Sen Hsuing; Prochnow, Luís Ignácio

    2009-01-01T23:59:59.000Z

    Pure gypsum Source average Phosphate Rock (100 mg kg -1 P)Pure gypsum Source average Phosphate Rock (100 mg kg -1 P) bPure gypsum Source average Phosphate Rock (100 mg kg -1 P)

  11. Z .Geoderma 96 2000 4761 The terminology and the concepts of gypsum-rich

    E-Print Network [OSTI]

    Ahmad, Sajjad

    earth-surface processes. q 2000 Elsevier Science B.V. All rights reserved. Keywords: gypsum; gypsiferous of soils and surficial formations containing gypsum is rarely considered in the global environmental December 1999 Abstract Many terms in earth sciences, and their underlying ideas, have been developed

  12. Manufacture of ammonium sulfate fertilizer from FGD-gypsum. Technical report, September 1--November 30, 1994

    SciTech Connect (OSTI)

    Chou, M.I.M.; Rostam-Abadi, M.; Lytle, J.M. [Illinois State Geological Survey, Champaign, IL (United States); Hoeft, R. [Illinois Univ., Urbana, IL (United States); Blevins, F.Z. [Allied-Signal, Inc., Morristown, NJ (United States); Achron, F. [Southeast Marketing Chemical Process, Inc. (United States)

    1994-12-31T23:59:59.000Z

    The overall goal of this project is to assess the technical and economic feasibility for producing commercial-grade ammonium sulfate fertilizer from gypsum produced as part of limestone flue gas desulfurization (FGD) processes. This is a cooperative effort among the ISGS, the UIUC, AlliedSignal, SE-ME, Henry Fertilizer, Illinois Power Co. (IP), and Central Illinois Public Services (CIPS). Bench-scale experiments will be conducted to obtain process engineering data for manufacture of ammonium sulfate from FGD-gypsum and to help evaluate technical and economical feasibility of the process. Controlled greenhouse experiments will be conducted at UIUC to evaluate the chemical impact of the produced ammonium sulfate on soil properties. A process flow sheet will be proposed and market demand for the products will be established. An engineering team at IP will provide an independent review of the economics of the process. AlliedSignal will be involved in testing and quality evaluation of ammonium sulfate samples and is interested in an agreement to market the finished product. CIPS will provide technical assistance and samples of FGD-gypsum for the project. In this quarter, a literature study that should give detailed insight into the chemistry, process schemes, and costs of producing ammonium sulfate from gypsum is in progress at the ISGS. Acquisition of a high quality FGD-gypsum sample was completed. Collecting of the other lower grade sample was scheduled to be conducted in December. Characterization of these feed materials is in progress.

  13. Gypsum Effect on the Aggregate Size and Geometry of Three Sodic Soils Under Reclamation

    E-Print Network [OSTI]

    Ahmad, Sajjad

    Gypsum Effect on the Aggregate Size and Geometry of Three Sodic Soils Under Reclamation I. Lebron- tion of clays occurs because of the repulsion of similarReclamation of sodic soils is imperative in many areas where deteri- charged clay platelets and the ability of the soil solutionoration of land

  14. Manufacture of ammonium sulfate fertilizer from FGD-gypsum. Technical report, March 1--May 31, 1995

    SciTech Connect (OSTI)

    Chou, M.I.M.; Rostam-Abadi, Ml; Lytle, J.M.; Bruinius, J.A.; Li, Y.C. [Illinois State Geological Survey, Urbana, IL (United States); Hoeft, R. [Illinois Univ., Urbana, IL (United States); Dewey, S. [AlliedSignal-Chemicals (United States); Achorn, F. [Southeast Marketing Chem. Process INc. (SE-ME) (United States)

    1995-12-31T23:59:59.000Z

    Goal is to assess technical and economic feasibility for producing fertilizer-grade ammonium sulfate from gypsum produced in limestone flue gas desulfurization (FGD). This is the 1st year of a 2-year program among Illinois State Geological Survey, University of Illinois (Urbana-Champaign), Allied-Signal, Marketing Chem. Process Inc., Henry Fertilizer, Illinois Power Co., and Central Illinois Public Services. In previous quarter, chemistry and process conditions were reviewed and a reactor system set up and used to conduct laboratory tests. FGD-gypsum from Abbott power plant was used. The scrubber, a Chiyoda Thoroughbred 121 FGD, produced a filter cake (98.36% gypsum and < 0.01% CaSO{sub 3}). Conversion of FGD- gypsum to ammonium sulfate was tested at 60-70{degree}C for 5-6 hr. Yield up to 82% and purity up to 95% were achieved for the ammonium sulfate production. During this quarter, more bench-scale experiments including a mass balance analysis were conducted; a yield up to 83% and up to 99% purity were achieved. A literature survey was completed and a preliminary process flow sheet was developed. Economics of the process is being estimated.

  15. GaAs photoconductive semiconductor switch

    DOE Patents [OSTI]

    Loubriel, G.M.; Baca, A.G.; Zutavern, F.J.

    1998-09-08T23:59:59.000Z

    A high gain, optically triggered, photoconductive semiconductor switch (PCSS) implemented in GaAs as a reverse-biased pin structure with a passivation layer above the intrinsic GaAs substrate in the gap between the two electrodes of the device is disclosed. The reverse-biased configuration in combination with the addition of the passivation layer greatly reduces surface current leakage that has been a problem for prior PCSS devices and enables employment of the much less expensive and more reliable DC charging systems instead of the pulsed charging systems that needed to be used with prior PCSS devices. 5 figs.

  16. GaAs photoconductive semiconductor switch

    DOE Patents [OSTI]

    Loubriel, Guillermo M. (Sandia Park, NM); Baca, Albert G. (Albuquerque, NM); Zutavern, Fred J. (Albuquerque, NM)

    1998-01-01T23:59:59.000Z

    A high gain, optically triggered, photoconductive semiconductor switch (PCSS) implemented in GaAs as a reverse-biased pin structure with a passivation layer above the intrinsic GaAs substrate in the gap between the two electrodes of the device. The reverse-biased configuration in combination with the addition of the passivation layer greatly reduces surface current leakage that has been a problem for prior PCSS devices and enables employment of the much less expensive and more reliable DC charging systems instead of the pulsed charging systems that needed to be used with prior PCSS devices.

  17. Surface Science Analysis of GaAs Photocathodes Following Sustained...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Analysis of GaAs Photocathodes Following Sustained Electron Beam Delivery. Abstract: Degradation of the photocathode materials employed in photoinjectors represents a challenge for...

  18. GyPSuM: A Detailed Tomographic Model of Mantle Density and Seismic Wave Speeds

    SciTech Connect (OSTI)

    Simmons, N A; Forte, A M; Boschi, L; Grand, S P

    2010-03-30T23:59:59.000Z

    GyPSuM is a tomographic model fo mantle seismic shear wave (S) speeds, compressional wave (P) speeds and detailed density anomalies that drive mantle flow. the model is developed through simultaneous inversion of seismic body wave travel times (P and S) and geodynamic observations while considering realistic mineral physics parameters linking the relative behavior of mantle properties (wave speeds and density). Geodynamic observations include the (up to degree 16) global free-air gravity field, divergence of the tectonic plates, dynamic topography of the free surface, and the flow-induced excess ellipticity of the core-mantle boundary. GyPSuM is built with the philosophy that heterogeneity that most closely resembles thermal variations is the simplest possible solution. Models of the density field from Earth's free oscillations have provided great insight into the density configuration of the mantle; but are limited to very long-wavelength solutions. Alternatively, simply scaling higher resolution seismic images to density anomalies generates density fields that do not satisfy geodynamic observations. The current study provides detailed density structures in the mantle while directly satisfying geodynamic observations through a joint seismic-geodynamic inversion process. Notable density field observations include high-density piles at the base of the superplume structures, supporting the fundamental results of past normal mode studies. However, these features are more localized and lower amplitude than past studies would suggest. When we consider all seismic anomalies in GyPSuM, we find that P and S-wave speeds are strongly correlated throughout the mantle. However, correlations between the high-velocity S zones in the deep mantle ({approx} 2000 km depth) and corresponding P-wave anomalies are very low suggesting a systematic divergence from simplified thermal effects in ancient subducted slab anomalies. Nevertheless, they argue that temperature variations are the primary cause of P-wave, S-wave, and density anomalies in the mantle.

  19. D10.7.2: Results for GaAs photocathodes

    E-Print Network [OSTI]

    Xiang, R

    2013-01-01T23:59:59.000Z

    HZDR plans to apply bulk GaAs photocathode in SRF gun for high current electron source. Supported by this project, a preparation system for GaAs photocathode has been developed. The cathode plugs special for GaAs wafer have been modified and proofed in SRF gun real running conditions. Virgin GaAs wafer was tested in the SRF gun cavity, and the first GaAs activation was performed.

  20. The development of integrated chemical microsensors in GaAs

    SciTech Connect (OSTI)

    CASALNUOVO,STEPHEN A.; ASON,GREGORY CHARLES; HELLER,EDWIN J.; HIETALA,VINCENT M.; BACA,ALBERT G.; HIETALA,S.L.

    1999-11-01T23:59:59.000Z

    Monolithic, integrated acoustic wave chemical microsensors are being developed on gallium arsenide (GaAs) substrates. With this approach, arrays of microsensors and the high frequency electronic components needed to operate them reside on a single substrate, increasing the range of detectable analytes, reducing overall system size, minimizing systematic errors, and simplifying assembly and packaging. GaAs is employed because it is both piezoelectric, a property required to produce the acoustic wave devices, and a semiconductor with a mature microelectronics fabrication technology. Many aspects of integrated GaAs chemical sensors have been investigated, including: surface acoustic wave (SAW) sensors; monolithic SAW delay line oscillators; GaAs application specific integrated circuits (ASIC) for sensor operation; a hybrid sensor array utilizing these ASICS; and the fully monolithic, integrated SAW array. Details of the design, fabrication, and performance of these devices are discussed. In addition, the ability to produce heteroepitaxial layers of GaAs and aluminum gallium arsenide (AlGaAs) makes possible micromachined membrane sensors with improved sensitivity compared to conventional SAW sensors. Micromachining techniques for fabricating flexural plate wave (FPW) and thickness shear mode (TSM) microsensors on thin GaAs membranes are presented and GaAs FPW delay line and TSM resonator performance is described.

  1. The use of gypsum and a coal desulfurization by-product to ameliorate subsoil acidity for alfalfa growth

    E-Print Network [OSTI]

    Chessman, Dennis John

    2004-09-30T23:59:59.000Z

    the effectiveness of surface-applied gypsum and a flue gas desulfurization by-product for reducing the toxic effects of acid subsoils on alfalfa. The materials were applied at rates of 0, 5, 10, and 15 Mg ha-1. In addition, a glasshouse experiment was conducted...

  2. Field dependent emission rates in radiation damaged GaAs

    SciTech Connect (OSTI)

    Fleming, R. M.; Myers, S. M.; Wampler, W. R.; Lang, D. V.; Seager, C. H.; Campbell, J. M. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1415 (United States)

    2014-07-07T23:59:59.000Z

    We have measured the temperature and field dependence of emission rates from five traps in electron damaged GaAs. Four of the traps have previously been identified as radiation defects. One of the traps, seen in higher doped diodes, has not been previously identified. We have fit the data to a multiphonon emission theory that allows recombination in GaAs to be characterized over a broad range of temperature and electric field. These results demonstrate an efficient method to calculate field-dependent emission rates in GaAs.

  3. Electrical degradation mechanisms of RF power GaAs PHEMTs

    E-Print Network [OSTI]

    Villanueva, Anita A. (Anita Ariel), 1978-

    2007-01-01T23:59:59.000Z

    GaAs Pseudomorphic High-Electron Mobility Transistors (PHEMTs) are widely used in RF power applications. Since these devices typically operate at high power levels and under high voltage biasing, their electrical reliability ...

  4. Nonlinear Terahertz Metamaterials via Field-Enhanced Carrier Dynamics in GaAs

    E-Print Network [OSTI]

    Fan, Kebin

    We demonstrate nonlinear metamaterial split ring resonators (SRRs) on GaAs at terahertz frequencies. For SRRs on doped GaAs films, incident terahertz radiation with peak fields of ?20–160??kV/cm drives intervalley scattering. ...

  5. TESLA-FEL 2007-03 Application of low cost GaAs LED as neutron

    E-Print Network [OSTI]

    neutrons in unbiased Gallium Arsenide (GaAs) Light Emitting Diodes (LED) resulted in a reduction Keywords: COTS components, Displacement damage, Electron Linear Accelerator, GaAs Light emitting diode (LED) Gallium Arsenide (GaAs) light emitting diode (LED) for the assessment of integrated neutron fluence

  6. Simple intrinsic defects in GaAs : numerical supplement.

    SciTech Connect (OSTI)

    Schultz, Peter Andrew

    2012-04-01T23:59:59.000Z

    This Report presents numerical tables summarizing properties of intrinsic defects in gallium arsenide, GaAs, as computed by density functional theory. This Report serves as a numerical supplement to the results published in: P.A. Schultz and O.A. von Lilienfeld, 'Simple intrinsic defects in GaAs', Modelling Simul. Mater. Sci Eng., Vol. 17, 084007 (2009), and intended for use as reference tables for a defect physics package in device models. The numerical results for density functional theory calculations of properties of simple intrinsic defects in gallium arsenide are presented.

  7. Ga nanoparticle-enhanced photoluminescence of GaAs

    SciTech Connect (OSTI)

    Kang, M.; Al-Heji, A. A.; Jeon, S.; Wu, J. H. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)] [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Lee, J.-E.; Saucer, T. W.; Zhao, L.; Sih, V. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)] [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States); Katzenstein, A. L. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, Eckerd College, St. Petersburg, Florida 33711-4744 (United States); Sofferman, D. L. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, Adelphi University, Garden City, New York 11530-0701 (United States); Goldman, R. S. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)

    2013-09-02T23:59:59.000Z

    We have examined the influence of surface Ga nanoparticles (NPs) on the enhancement of GaAs photoluminescence (PL) efficiency. We have utilized off-normal focused-ion-beam irradiation of GaAs surfaces to fabricate close-packed Ga NP arrays. The enhancement in PL efficiency is inversely proportional to the Ga NP diameter. The maximum PL enhancement occurs for the Ga NP diameter predicted to maximize the incident electromagnetic (EM) field enhancement. The PL enhancement is driven by the surface plasmon resonance (SPR)-induced enhancement of the incident EM field which overwhelms the SPR-induced suppression of the light emission.

  8. Gallium Arsenide (GaAs) EDWARD D. PALIK

    E-Print Network [OSTI]

    Pulfrey, David L.

    constants of pure (semi-insulating) GaAs are derived from a number of papers including the far-infrared at. [4]; the near-IR work of Pikhtin and Yas'kov [5]; the calorim- etry work of Christensen et al. [6 reflection work of Philipp and Ehrenreich [9]; and the synchrotron transmission work of Cardona et al. [10

  9. Response of GaAs to fast intense laser pulses

    E-Print Network [OSTI]

    Graves, JS; Allen, Roland E.

    1998-01-01T23:59:59.000Z

    . The Hamiltonian is H ~ r !5 S ?1 V~r ! V ~ r ! ?2 D , ~1.1! so the bonding and antibonding states have energies ? 6 5 1 2 ~?11?2!6 1 2 @~?12?2! 2 14V ~ r !2#1/2. ~1.2! PRB 580163-1829/98/58~20!/13627~7!/$15.00 t intense laser pulses R. E... to TABLE II. Repulsive potential parameters for GaAs and Si. These values are appropriate when distances are measured in ? and energies in eV. a b g GaAs 263.7 -1227.5 3653.1 Si 263.2 -1027.0 2631.8 PRB 58D R. E. ALLEN an intense laser pulse...

  10. Accurate characterization and improvement of GaAs microstrip attenuation

    E-Print Network [OSTI]

    Carroll, James Mason

    1992-01-01T23:59:59.000Z

    Mason Carroll, B. S. , Rose-Hulman Institute of Technology Chair of Advisory Committee: Dr. Kai Chang Microstrip transmission lines are widely used in microv, ave circuits. The high frequencies cause the microstrip characteristics, especially... OF CONTENTS . . LIST OF FIGURES LIST OF TABLES. . CHAPTER I INTRODUCTION . . I. A Introduction. I. B Thesis Research Il GaAs MICROSTRlp ATTENUATION . II. A Characterization ol'Transmission Line Attenuation. . . . II. A. I Introduction. II. A. 2...

  11. Bandgap and band discontinuity in wurtzite/zincblende GaAs homomaterial heterostructure

    E-Print Network [OSTI]

    Shalish, Ilan

    Bandgap and band discontinuity in wurtzite/zincblende GaAs homomaterial heterostructure Ron Gurwitz (Received 28 January 2012; accepted 21 April 2012; published online 9 May 2012) A wurtzite GaAs epilayer photovoltage spectroscopy. The wurtzite structure of the epilayer is disclosed by scanning electron microscope

  12. Band offsets at zincblende-wurtzite GaAs nanowire sidewall surfaces P. Capiod,1

    E-Print Network [OSTI]

    Dunin-Borkowski, Rafal E.

    Band offsets at zincblende-wurtzite GaAs nanowire sidewall surfaces P. Capiod,1 T. Xu,1,2 J. P. Nys of zincblende (ZB)-wurtzite (WZ) GaAs nanowires are investigated by scanning tunneling spectroscopy and density inclusions consisting of zinc-blende (ZB) and wurtzite (WZ) segments form during the growth of NWs and where

  13. KrF-laser annealing of native oxides on GaAs

    SciTech Connect (OSTI)

    Ahrenkiel, R.K.; Anderson, G.; Dunlavy, D.; Maggiore, C.; Hammond, R.B.; Stotlar, S.

    1980-01-01T23:59:59.000Z

    Annealing of native oxides grown on GaAs has been performed using a pulsed KrF laser. This process allows the oxides to be heated to temperatures well above 350/sup 0/C without arsenic loss from the GaAs substrate. The physical, chemical, and electronic properties of the oxide are markedly changed by laser processing.

  14. Crack formation in GaAs heteroepitaxial films on Si and SiGe virtual substrates

    E-Print Network [OSTI]

    Crack formation in GaAs heteroepitaxial films on Si and SiGe virtual substrates V. K. Yang, MAs films grown on Si and SiGe virtual substrates analytically and experimentally. The analytical model­10 Relaxed SiGe graded layers on Si have produced the highest quality GaAs on Si to date for the integration

  15. Back contacted and small form factor GAAS solar cell.

    SciTech Connect (OSTI)

    Clews, Peggy Jane; Wanlass, Mark W. (National Renewable Energy Laboratory); Sanchez, Carlos A.; Pluym, Tammy; Cruz-Campa, Jose Luis; Okandan, Murat; Gupta, Vipin P.; Nielson, Gregory N.; Resnick, Paul James

    2010-06-01T23:59:59.000Z

    We present a newly developed microsystem enabled, back-contacted, shade-free GaAs solar cell. Using microsystem tools, we created sturdy 3 {micro}m thick devices with lateral dimensions of 250 {micro}m, 500 {micro}m, 1 mm, and 2 mm. The fabrication procedure and the results of characterization tests are discussed. The highest efficiency cell had a lateral size of 500 {micro}m and a conversion efficiency of 10%, open circuit voltage of 0.9 V and a current density of 14.9 mA/cm{sup 2} under one-sun illumination.

  16. Quantum effects in electron beam pumped GaAs

    SciTech Connect (OSTI)

    Yahia, M. E. [Faculty of Engineering, The British University in Egypt (BUE), El-Shorouk City, Cairo (Egypt) [Faculty of Engineering, The British University in Egypt (BUE), El-Shorouk City, Cairo (Egypt); National Institute of Laser Enhanced Sciences (NILES), Cairo University (Egypt); Azzouz, I. M. [National Institute of Laser Enhanced Sciences (NILES), Cairo University (Egypt)] [National Institute of Laser Enhanced Sciences (NILES), Cairo University (Egypt); Moslem, W. M. [Department of Physics, Faculty of Science, Port Said University, Port Said (Egypt)] [Department of Physics, Faculty of Science, Port Said University, Port Said (Egypt)

    2013-08-19T23:59:59.000Z

    Propagation of waves in nano-sized GaAs semiconductor induced by electron beam are investigated. A dispersion relation is derived by using quantum hydrodynamics equations including the electrons and holes quantum recoil effects, exchange-correlation potentials, and degenerate pressures. It is found that the propagating modes are instable and strongly depend on the electron beam parameters, as well as the quantum recoil effects and degenerate pressures. The instability region shrinks with the increase of the semiconductor number density. The instability arises because of the energetic electron beam produces electron-hole pairs, which do not keep in phase with the electrostatic potential arising from the pair plasma.

  17. Evolution Of Surface Topography On GaAs(100) And GaAs(111) At Normal And Oblique Incidence Of Ar{sup +}-Ions

    SciTech Connect (OSTI)

    Venugopal, V.; Basu, T.; Garg, S.; Majumder, S.; Sarangi, S. N.; Som, T. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751 005 (India); Das, P.; Bhattacharyya, S. R.; Chini, T. K. [Surface Physics Division, Saha Institute of Nuclear Physics, Kolkata 700 064 (India)

    2010-10-04T23:59:59.000Z

    Nanoscale surface structures emerging from medium energy (50-60 keV)Ar{sup +}-ion sputtering of p-type GaAs(100) and semi-insulating GaAs(111) substrates have been investigated. For normally incident 50 keV Ar{sup +}-ions of fluence 1x10{sup 17} ions/cm{sup 2} on GaAs(100) and GaAs(111) features in the form of nanoscale pits/holes without short range ordering are observed with densities 5.2x10{sup 9} /cm{sup 2} and 5.9x10{sup 9} /cm{sup 2}, respectively along with irregularly shaped patches of islands. For GaAs(111) on increasing the influence to 5x10{sup 17} /cm{sup 2} the pit density increases marginally to 6.2x10{sup 9} /cm{sup 2}. For 60 deg. off-normal incidence of 60 keV Ar.{sup +}-ions of fluence 2x10{sup 17} ions/cm{sup 2} on GaAs(100) microscale wavelike surface topography is observed. In all cases well-defined nanodots are absent on the surface.

  18. Terahertz waveguide spectroscopy of two-dimensional plasmons in GaAs

    E-Print Network [OSTI]

    Harris, C. Thomas (Charles Thomas)

    2010-01-01T23:59:59.000Z

    The electrical characteristics of high-mobility, two-dimensional electron gas (2DEG) systems, such as GaAs quantum wells, have been well-studied at low frequencies and in extreme conditions of high magnetic fields and ...

  19. Exciton localization mechanisms in wurtzite/zinc-blende GaAs nanowires

    E-Print Network [OSTI]

    Graham, Alexandra; Corfdir, Pierre; Heiss, Martin; Conesa-Boj, Sonia; Uccelli, Emanuele; Fontcuberta i Morral, Anna; Phillips, Richard

    We investigate the emission properties of excitons in GaAs nanowires containing quantum disks formed by structural alternation between the zinc-blende and wurtzite phases, by means of temperature-dependent photoluminescence. At 10 K the emission...

  20. Molecular Dynamics Simulation of GaAs Molecular Beam Epitaxy D. A. Murdick,1

    E-Print Network [OSTI]

    Wadley, Haydn

    of Virginia, Charlottesville, Virginia 22904, USA 2 Department of Materials, University of Oxford, Oxford OX1 3PH, UK ABSTRACT The vapor deposition of epitaxial GaAs and (Ga,Mn)As thin films during far-temperature growth of Ga0.94Mn0.06As and the Mn clustering trends in as-grown films. INTRODUCTION GaAs is widely used

  1. A study of microstrip T-juction discontinuity effects and modeling on GAAS substrates

    E-Print Network [OSTI]

    Guill, Dennis Jarrett

    1999-01-01T23:59:59.000Z

    A STUDY OF MICROSTRIP T-JUNCTION DISCONTINUITY EFFECTS AND MODELING ON GAAS SUBSTRATES A Thesis by DENNIS JARRET GUILL IR. Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE December 1999 Major Subject: Electrical Engineering A STUDY OF MICROSTRIP T-JUNCTION DISCONTINUITY EFFECTS AND MODELING ON GAAS SUBSTRATES A Thesis by DENNIS JARRET GUILL JR. Submitted to Texas A&M University...

  2. Development of high-efficiency GaAs solar cells on polycrystalline Ge substrates

    SciTech Connect (OSTI)

    Venkatasubramanian, R.; OQuinn, B.; Hills, J.; Malta, D.; Timmons, M.L.; Hutchby, J.A. [Research Triangle Institute, Research Triangle Park, North Carolina 27709 (United States); Ahrenkiel, R.; Keyes, B.M. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

    1996-01-01T23:59:59.000Z

    Progress in the development of high-efficiency GaAs solar cells on low-cost, large-area, large-grain, optical-grade polycrystalline Ge substrates is described in this paper. First, we present results on the growth of specular GaAs-AlGaAs layers, across the various crystalline orientations of a polycrystalline Ge substrate, by metallorganic chemical vapor deposition (MOCVD). Second, we present the preliminary optimization of minority-carrier properties of GaAs-AlGaAs structures on poly-Ge substrates towards the improvement of GaAs solar cells. We have demonstrated comparable minority-carrier lifetimes in GaAs double-hetero structures grown on optical-grade poly-Ge substrates and electronic-grade single-crystal Ge substrates. In addition, we describe device-structure optimization that have led us to achieve a open-circuit voltage of {approximately}1 Volt in a GaAs solar cell on poly-Ge and to improve our previous best efficiency from 15.8{percent} for a 1-cm{sup 2}-area GaAs cell to 16.7{percent} for a 4-cm{sup 2}-area GaAs solar cell on poly-Ge. {copyright} {ital 1996 American Institute of Physics.}

  3. Defect studies in low-temperature-grown GaAs

    SciTech Connect (OSTI)

    Bliss, D.E.

    1992-11-01T23:59:59.000Z

    High content of excess As is incorporated in GaAs grown by low-temperature molecular-beam-epitaxy (LTMBE). The excess As exists primarily as As antisite defects AsGa and a lesser extent of gallium vacancies V[sub Ga]. The neutral AsGa-related defects were measured by infrared absorption at 1[mu]m. Gallium vacancies, V[sub Ga], was investigated by slow positron annihilation. Dependence of defect contents on doping was studied by Si and Be dopants. No free carriers are generated by n-type or p-type doping up to 10[sup 19] cm[sup [minus]3] Si or Be. Raman data indicate Be occupies Ga substitutional sites but Si atom is not substitutional. Si induces more As[sub Ga] in the layer. As As[sub Ga] increases, photoquenchable As[sub Ga] decreases. Fraction of photoquenchable defects correlates to defects within 3 nearest neighbor separations disrupting the metastability. Annealing reduces neutral As[sub Ga] content around 500C, similar to irradiation damaged and plastically deformed Ga[sub As], as opposed to bulk grown GaAs in which As[sub Ga]-related defects are stable up to 1100C. The lower temperature defect removal is due to V[sub Ga] enhanced diffusion of As[sub Ga] to As precipitates. The supersaturated V[sub GA] and also decreases during annealing. Annealing kinetics for As[sub Ga]-related defects gives 2.0 [plus minus] 0.3 eV and 1.5 [plus minus] 0.3 eV migration enthalpies for the As[sub Ga] and V[sub Ga]. This represents the difference between Ga and As atoms hopping into the vacancy. The non-photoquenchable As[sub Ga]-related defects anneal with an activation energy of 1.1 [plus minus] 0.3eV. Be acceptors can be activated by 800C annealing. Temperature difference between defect annealing and Be activation formation of As[sub Ga]-Be[sub Ga] pairs. Si donors can only be partially activated.

  4. Metal-insulator-semiconductor structures on p-type GaAs with low interface state density

    E-Print Network [OSTI]

    Chen, Zhi

    Metal-insulator-semiconductor structures on p-type GaAs with low interface state density Zhi Chen properties of in situ deposited Si3N4 /Si/p-GaAs metal-insulator-semiconductor structures have been offered by a low gate leakage technology in GaAs, such as metal insulator structures, func- tional Ga

  5. Evolution of ion-induced nanoparticle arrays on GaAs surfaces

    SciTech Connect (OSTI)

    Kang, M.; Al-Heji, A. A.; Shende, O.; Huang, S.; Jeon, S.; Goldman, R. S., E-mail: rsgold@umich.edu [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Beskin, I. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)

    2014-05-05T23:59:59.000Z

    We have examined the evolution of irradiation-induced Ga nanoparticle (NP) arrays on GaAs surfaces. Focused-ion-beam irradiation of pre-patterned GaAs surfaces induces monotonic increases in the NP volume and aspect ratio up to a saturation ion dose, independent of NP location within the array. Beyond the saturation ion dose, the NP volume continues to increase monotonically while the NP aspect ratio decreases monotonically. In addition, the NP volumes (aspect ratios) are highest (lowest) for the corner NPs. We discuss the relative influences of bulk and surface diffusion on the evolution of Ga NP arrays.

  6. Second harmonic generation in photonic crystal cavities in (111)-oriented GaAs

    SciTech Connect (OSTI)

    Buckley, Sonia, E-mail: bucklesm@stanford.edu; Radulaski, Marina; Vu?kovi?, Jelena [E. L. Ginzton Laboratory, Stanford University, Stanford, California 94305 (United States)] [E. L. Ginzton Laboratory, Stanford University, Stanford, California 94305 (United States); Biermann, Klaus [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany)] [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany)

    2013-11-18T23:59:59.000Z

    We demonstrate second harmonic generation at telecommunications wavelengths in photonic crystal cavities in (111)-oriented GaAs. We fabricate 30 photonic crystal structures in both (111)- and (100)-oriented GaAs and observe an increase in generated second harmonic power in the (111) orientation, with the mean power increased by a factor of 3, although there is a large scatter in the measured values. We discuss possible reasons for this increase, in particular, the reduced two photon absorption for transverse electric modes in (111) orientation, as well as a potential increase due to improved mode overlap.

  7. Biexciton emission from single isoelectronic traps formed by nitrogen-nitrogen pairs in GaAs

    SciTech Connect (OSTI)

    Takamiya, Kengo; Fukushima, Toshiyuki; Yagi, Shuhei; Hijikata, Yasuto; Yaguchi, Hiroyuki [Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku , Saitama 338-8570 (Japan); Mochizuki, Toshimitsu; Yoshita, Masahiro; Akiyama, Hidefumi [Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Kuboya, Shigeyuki; Onabe, Kentaro [Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Katayama, Ryuji [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2013-12-04T23:59:59.000Z

    We have studied photoluminescence (PL) from individual isoelectronic traps formed by nitrogen-nitrogen (NN) pairs in GaAs. Sharp emission lines due to exciton and biexciton were observed from individual isoelectronic traps in nitrogen atomic-layer doped (ALD) GaAs. The binding energy of biexciton bound to individual isoelectronic traps was approximately 8 meV. Both the exciton and biexciton luminescence lines show completely random polarization and no fine-structure splitting. These results are desirable to the application to the quantum cryptography used in the field of quantum information technology.

  8. GaAs photovoltaics and optoelectronics using releasable multilayer epitaxial assemblies

    E-Print Network [OSTI]

    Rogers, John A.

    LETTERS GaAs photovoltaics and optoelectronics using releasable multilayer epitaxial assemblies and high electron mobilities. Examples range from effi- cient photovoltaic devices1,2 to radio and logic gates on plates of glass, near-infrared imaging devices on wafers of silicon, and photovoltaic

  9. Dynamics of Subsurface and Surface Chemisorption for B, C, and N on Gaas and Inp

    E-Print Network [OSTI]

    MENON, M.; Allen, Roland E.

    1991-01-01T23:59:59.000Z

    on GaAs. H=HO+ V, @11 0 0 0 (2.7) (2.8) The Green's function for this system is G =(el ?H ) (2.9) Let H be the 1V XX Hamiltonian matrix for a large sys- tem (N~ ~ here). We suppose that H differs from an unperturbed Hamiltonian Ho only in some...

  10. SSL/TLS Session-Aware User Authentication Using a GAA Bootstrapped Key

    E-Print Network [OSTI]

    Sheldon, Nathan D.

    SSL/TLS Session-Aware User Authentication Using a GAA Bootstrapped Key Chunhua Chen1 , Chris J.mitchell@rhul.ac.uk Abstract. Most SSL/TLS-based electronic commerce (e-commerce) ap- plications (including Internet banking a server effectively, and because user authentication methods are typi- cally decoupled from SSL

  11. Surface Science 415 (1998) 2936 Structural studies of sulfur-passivated GaAs (100)

    E-Print Network [OSTI]

    Zhang, Yanchao

    1998-01-01T23:59:59.000Z

    . Keywords: Atomic force microscopy; Gallium arsenide; Low-energy electron diffraction; Roughness; SulfurSurface Science 415 (1998) 29­36 Structural studies of sulfur-passivated GaAs (100) surfaces Abstract We present the results of Auger electron spectroscopy (AES), low-energy electron diffraction (LEED

  12. Measurement of Electron Beam Polarization from Unstrained Bulk GaAs via Two Photon Photoemission

    E-Print Network [OSTI]

    Gay, Timothy J.

    the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab, where the polarized electron beamMeasurement of Electron Beam Polarization from Unstrained Bulk GaAs via Two Photon Photoemission Collections Journals About Contact us My IOPscience #12;Measurement of Electron Beam Polarization from

  13. ORIGINAL ARTICLE Highly efficient GaAs solar cells by limiting light emission

    E-Print Network [OSTI]

    Atwater, Harry

    ORIGINAL ARTICLE Highly efficient GaAs solar cells by limiting light emission angle Emily D Kosten1. This isotropic emission corresponds to a significant entropy increase in the solar cell, with a corresponding drop in efficiency. Here, using a detailed balance model, we show that limiting the emission angle

  14. Experimental demonstration of enhanced photon recycling in angle-restricted GaAs solar cells

    E-Print Network [OSTI]

    Faraon, Andrei

    Experimental demonstration of enhanced photon recycling in angle-restricted GaAs solar cells Emily, emphasizing the optical nature of the effect. 1 Introduction For ideal solar cells where all recombination. Despite this theoretical prediction, until recently even the highest efficiency solar cells were not close

  15. Surface science analysis of GaAs photocathodes following sustained electron beam delivery

    SciTech Connect (OSTI)

    Carlos Hernandez-Garcia, Fay Hannon, Marcy Stutzman, V. Shutthanandan, Z. Zhu, M. Nandasri, S. V. Kuchibhatla, S. Thevuthasan, W. P. Hess

    2012-06-01T23:59:59.000Z

    Degradation of the photocathode materials employed in photoinjectors represents a challenge for sustained operation of nuclear physics accelerators and high power Free Electron Lasers (FEL). Photocathode quantum efficiency (QE) degradation is due to residual gasses in the electron source vacuum system being ionized and accelerated back to the photocathode. These investigations are a first attempt to characterize the nature of the photocathode degradation, and employ multiple surface and bulk analysis techniques to investigate damage mechanisms including sputtering of the Cs-oxidant surface monolayer, other surface chemistry effects, and ion implantation. Surface and bulk analysis studies were conducted on two GaAs photocathodes, which were removed from the JLab FEL DC photoemission gun after delivering electron beam, and two control samples. The analysis techniques include Helium Ion Microscopy (HIM), Rutherford Backscattering Spectrometry (RBS), Atomic Force Microscopy (AFM) and Secondary Ion Mass Spectrometry (SIMS). In addition, two high-polarization strained superlattice GaAs photocathode samples, one removed from the Continuous Electron Beam Accelerator Facility (CEBAF) photoinjector and one unused, were also analyzed using Transmission Electron Microscopy (TEM) and SIMS. It was found that heat cleaning the FEL GaAs wafer introduces surface roughness, which seems to be reduced by prolonged use. The bulk GaAs samples retained a fairly well organized crystalline structure after delivering beam but shows evidence of Cs depletion on the surface. Within the precision of the SIMS and RBS measurements the data showed no indication of hydrogen implantation or lattice damage from ion back bombardment in the bulk GaAs wafers. In contrast, SIMS and TEM measurements of the strained superlattice photocathode show clear crystal damage in the wafer from ion back bombardment.

  16. Femtosecond-scale response of GaAs to ultrafast laser pulses RID A-7793-2008

    E-Print Network [OSTI]

    Dumitrica, T.; Allen, Roland E.

    2002-01-01T23:59:59.000Z

    We present nonadiabatic simulations of the coherent response of crystalline GaAs irradiated by intense femtosecond-scale laser pulses. Above a threshold fluence, which corresponds to promotion of about 12% of the valence electrons...

  17. Nanometer-scale GaAs clusters from organometallic precursors Peter C. Sercel, Winston A. Saunders, Harry A. Atwater,

    E-Print Network [OSTI]

    Atwater, Harry

    the first direct observation of gas-phase ho- mogeneous nucleation of GaAs by the thermophoretic col thermophoret- ically on a holey carbon film which is mounted on a stain- less steel fixture aligned coaxially

  18. Comparison of strong coupling regimes in bulk GaAs, GaN and ZnO semiconductor microcavities

    E-Print Network [OSTI]

    Boyer, Edmond

    , transmission and absorption spectra of bulk GaAs, GaN and ZnO microcavities, in order to compareComparison of strong coupling regimes in bulk GaAs, GaN and ZnO semiconductor microcavities SAs and GaN microcavities. PACS numbers: 78.67.-n, 71.36.+c, 78.20.Ci, 78.55.Cr, 78.55.Et Keywords: polariton

  19. Gallium surface diffusion on GaAs (001) surfaces measured by crystallization dynamics of Ga droplets

    SciTech Connect (OSTI)

    Bietti, Sergio, E-mail: sergio.bietti@mater.unimib.it; Somaschini, Claudio; Esposito, Luca; Sanguinetti, Stefano [L–NESS and Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, Via Cozzi 55, I–20125 Milano (Italy); Fedorov, Alexey [L–NESS and CNR–IFN, via Anzani 42, I-22100 Como (Italy)

    2014-09-21T23:59:59.000Z

    We present accurate measurements of Ga cation surface diffusion on GaAs surfaces. The measurement method relies on atomic force microscopy measurement of the morphology of nano–disks that evolve, under group V supply, from nanoscale group III droplets, earlier deposited on the substrate surface. The dependence of the radius of such nano-droplets on crystallization conditions gives direct access to Ga diffusion length. We found an activation energy for Ga on GaAs(001) diffusion E{sub A}=1.31±0.15 eV, a diffusivity prefactor of D{sub 0}?=?0.53(×2.1±1) cm{sup 2} s{sup ?1} that we compare with the values present in literature. The obtained results permit to better understand the fundamental physics governing the motion of group III ad–atoms on III–V crystal surfaces and the fabrication of designable nanostructures.

  20. Epitaxial two-dimensional nitrogen atomic sheet in GaAs

    SciTech Connect (OSTI)

    Harada, Yukihiro, E-mail: y.harada@eedept.kobe-u.ac.jp; Yamamoto, Masuki; Baba, Takeshi; Kita, Takashi [Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan)

    2014-01-27T23:59:59.000Z

    We have grown an epitaxial two-dimensional nitrogen (N) atomic sheet in GaAs by using the site-controlled N ?-doping technique. We observed a change of the electronic states in N ?-doped GaAs from the isolated impurity centers to the delocalized impurity band at 1.49?eV with increasing N-doping density. According to the excitation-power- and temperature-dependent photoluminescence (PL) spectra, the emission related to localized levels below the impurity band edge was dominant at low excitation power and temperature, whereas the effects of the localized levels can be neglected by increasing the excitation power and temperature. Furthermore, a clear Landau shift of the PL-peak energy was observed at several Tesla in the Faraday configuration, in contrast to the case in the impurity limit.

  1. Cavity nucleation and evolution in He-implanted Si and GaAs

    SciTech Connect (OSTI)

    Follstaedt, D.M.; Myers, S.M.; Petersen, G.A.; Barbour, J.C.

    1995-12-01T23:59:59.000Z

    The criteria for forming stable cavities by He{sup +} implantation and annealing are examined for Si and GaAs. In Si, implanting at room temperature requires a minimum of 1.6 at. % He to form a continuous layer of cavities after annealing at 700{degrees}C. The cavities are located at dislocations and planar defects. Implanting peak He concentrations just above this threshold produces narrow layers of cavities at the projected range. In GaAs, room-temperature implantation followed by annealing results in exfoliation of the surface layer. Cavities were formed instead by implanting Ar followed by overlapping He, both at 400{degrees}C, with additional annealing at 400{degrees}C to outgas the He. This method forms 1.5--3.5 nm cavities that are often on [111] planar defects.

  2. Effects of atomic hydrogen and deuterium exposure on high polarization GaAs photocathodes

    SciTech Connect (OSTI)

    M. Baylac; P. Adderley; J. Brittian; J. Clark; T. Day; J. Grames; J. Hansknecht; M. Poelker; M. Stutzman; A. T. Wu; A. S. Terekhov

    2005-12-01T23:59:59.000Z

    Strained-layer GaAs and strained-superlattice GaAs photocathodes are used at Jefferson Laboratory to create high average current beams of highly spin-polarized electrons. High electron yield, or quantum efficiency (QE), is obtained only when the photocathode surface is atomically clean. For years, exposure to atomic hydrogen or deuterium has been the photocathode cleaning technique employed at Jefferson Laboratory. This work demonstrates that atomic hydrogen cleaning is not necessary when precautions are taken to ensure that clean photocathode material from the vendor is not inadvertently dirtied while samples are prepared for installation inside photoemission guns. Moreover, this work demonstrates that QE and beam polarization can be significantly reduced when clean high-polarization photocathode material is exposed to atomic hydrogen from an rf dissociator-style atomic hydrogen source. Surface analysis provides some insight into the mechanisms that degrade QE and polarization due to atomic hydrogen cleaning.

  3. Identification of As-vacancy complexes in Zn-diffused GaAs

    SciTech Connect (OSTI)

    Elsayed, M. [Department of Physics, Martin Luther University Halle, 06099 Halle (Germany); Department of Physics, Faculty of Science, Minia University, 61519 Minia (Egypt); Krause-Rehberg, R. [Department of Physics, Martin Luther University Halle, 06099 Halle (Germany); Korff, B. [Bremen Center for Computational Materials Science, University Bremen, 28359 Bremen (Germany); Richter, S. [Fraunhofer Center for Silicon Photovoltaics CSP, 06120 Halle (Saale) (Germany); Leipner, H. S. [Center of Materials Science, Martin Luther University Halle, 06099 Halle (Germany)

    2013-03-07T23:59:59.000Z

    We have used positron annihilation spectroscopy to study the introduction of point defects in Zn-diffused semi-insulating GaAs. The diffusion was performed by annealing the samples for 2 h at 950 Degree-Sign C. The samples were etched in steps of 7 {mu}m. Both Doppler broadening using slow positron beam and lifetime spectroscopy studies were performed after each etching step. Both techniques showed the existence of vacancy-type defects in a layer of about 45 {mu}m. Secondary ion mass spectroscopy measurements illustrated the presence of Zn at high level in the sample almost up to the same depth. Vacancy-like defects as well as shallow positron traps were observed by lifetime measurements. We distinguish two kinds of defects: As vacancy belongs to defect complex, bound to most likely one Zn atom incorporated on Ga sublattice, and negative-ion-type positron traps. Zn acceptors explained the observation of shallow traps. The effect of Zn was evidenced by probing GaAs samples annealed under similar conditions but without Zn treatment. A defect-free bulk lifetime value is detected in this sample. Moreover, our positron annihilation spectroscopy measurements demonstrate that Zn diffusion in GaAs system is governed by kick-out mechanism.

  4. High mobility single-crystalline-like GaAs thin films on inexpensive flexible metal substrates by metal-organic chemical vapor deposition

    SciTech Connect (OSTI)

    Dutta, P., E-mail: pdutta2@central.uh.edu; Rathi, M.; Gao, Y.; Yao, Y.; Selvamanickam, V. [Department of Mechanical Engineering, University of Houston, Houston, Texas 77204 (United States); Zheng, N.; Ahrenkiel, P. [Department of Nanoscience and Nanoengineering, South Dakota School of Mines and Technology, Rapid City, South Dakota 57701 (United States); Martinez, J. [Materials Evaluation Laboratory, NASA Johnson Space Center, Houston, Texas 77085 (United States)

    2014-09-01T23:59:59.000Z

    We demonstrate heteroepitaxial growth of single-crystalline-like n and p-type doped GaAs thin films on inexpensive, flexible, and light-weight metal foils by metal-organic chemical vapor deposition. Single-crystalline-like Ge thin film on biaxially textured templates made by ion beam assisted deposition on metal foil served as the epitaxy enabling substrate for GaAs growth. The GaAs films exhibited strong (004) preferred orientation, sharp in-plane texture, low grain misorientation, strong photoluminescence, and a defect density of ?10{sup 7?}cm{sup ?2}. Furthermore, the GaAs films exhibited hole and electron mobilities as high as 66 and 300?cm{sup 2}/V-s, respectively. High mobility single-crystalline-like GaAs thin films on inexpensive metal substrates can pave the path for roll-to-roll manufacturing of flexible III-V solar cells for the mainstream photovoltaics market.

  5. Engineering direct-indirect band gap transition in wurtzite GaAs nanowires through size and uniaxial strain

    E-Print Network [OSTI]

    Copple, Andrew; Peng, Xihong; 10.1063/1.4718026

    2012-01-01T23:59:59.000Z

    Electronic structures of wurtzite GaAs nanowires in the [0001] direction were studied using first-principles calculations. It was found that the band gap of GaAs nanowires experience a direct-to-indirect transition when the diameter of the nanowires is smaller than ~28 {\\AA}. For those thin GaAs nanowires with an indirect band gap, it was found that the gap can be tuned to be direct if a moderate external uniaxial strain is applied. Both tensile and compressive strain can trigger the indirect-to-direct gap transition. The critical strains for the gap-transition are determined by the energy crossover of two states in conduction bands.

  6. Back-contacted and small form factor GaAs solar cell.

    SciTech Connect (OSTI)

    Clews, Peggy Jane; Wanlass, Mark W. (National Renewable Energy Laboratory, Golden, CO); Sanchez, Carlos A.; Pluym, Tammy; Cruz-Campa, Jose Luis; Okandan, Murat; Gupta, Vipin P.; Nielson, Gregory N.; Resnick, Paul James

    2010-07-01T23:59:59.000Z

    We present a newly developed microsystem enabled, back-contacted, shade-free GaAs solar cell. Using microsystem tools, we created sturdy 3 {micro}m thick devices with lateral dimensions of 250 {micro}m, 500 {micro}m, 1 mm, and 2 mm. The fabrication procedure and the results of characterization tests are discussed. The highest efficiency cell had a lateral size of 500 {micro}m and a conversion efficiency of 10%, open circuit voltage of 0.9 V and a current density of 14.9 mA/cm{sup 2} under one-sun illumination.

  7. Ultrafast magneto-photocurrents in GaAs: Separation of surface and bulk contributions

    E-Print Network [OSTI]

    Schmidt, Christian B; Tarasenko, Sergey A; Bieler, Mark

    2015-01-01T23:59:59.000Z

    We induce ultrafast magneto-photocurrents in a GaAs crystal employing interband excitation with femtosecond laser pulses at room temperature and non-invasively separate surface and bulk contributions to the overall current response. The separation between the different symmetry contributions is achieved by measuring the simultaneously emitted terahertz radiation for different sample orientations. Excitation intensity and photon energy dependences of the magneto-photocurrents for linearly and circularly polarized excitations reveal an involvement of different microscopic origins, one of which we believe is the inverse Spin-Hall effect. Our experiments are important for a better understanding of the complex momentum-space carrier dynamics in magnetic fields.

  8. High excitation power photoluminescence studies of ultra-low density GaAs quantum dots

    SciTech Connect (OSTI)

    Sonnenberg, D.; Graf, A.; Paulava, V.; Heyn, Ch.; Hansen, W. [Institut für Angewandte Physik und Zentrum für Mikrostrukturforschung, Universität Hamburg, Jungiusstr. 11, 20355 Hamburg (Germany)

    2013-12-04T23:59:59.000Z

    We fabricate GaAs epitaxial quantum dots (QDs) by filling of self-organized nanoholes in AlGaAs. The QDs are fabricated under optimized process conditions and have ultra-low density in the 10{sup 6} cm{sup ?2} regime. At low excitation power the optical emission of single QDs exhibit sharp excitonic lines, which are attributed to the recombination of excitonic and biexcitonic states. High excitation power measurements reveal surprisingly broad emission lines from at least six QD shell states.

  9. Origins of ion irradiation-induced Ga nanoparticle motion on GaAs surfaces

    SciTech Connect (OSTI)

    Kang, M.; Wu, J. H.; Chen, H. Y.; Thornton, K.; Goldman, R. S. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)] [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Sofferman, D. L. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, Adelphi University, Garden City, New York 11530-0701 (United States); Beskin, I. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)] [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)

    2013-08-12T23:59:59.000Z

    We have examined the origins of ion irradiation-induced nanoparticle (NP) motion. Focused-ion-beam irradiation of GaAs surfaces induces random walks of Ga NPs, which are biased in the direction opposite to that of ion beam scanning. Although the instantaneous NP velocities are constant, the NP drift velocities are dependent on the off-normal irradiation angle, likely due to a difference in surface non-stoichiometry induced by the irradiation angle dependence of the sputtering yield. It is hypothesized that the random walks are initiated by ion irradiation-induced thermal fluctuations, with biasing driven by anisotropic mass transport.

  10. Picosecond buildup and relaxation of intense stimulated emission in GaAs

    SciTech Connect (OSTI)

    Ageeva, N. N.; Bronevoi, I. L., E-mail: bil@cplire.ru; Zabegaev, D. N.; Krivonosov, A. N. [Russian Academy of Sciences, Kotelnikov Institute of Radio Engineering and Electronics (Russian Federation)

    2013-04-15T23:59:59.000Z

    In support of the idea developed previously based on circumstantial evidence, we have found that stimulated emission emerges in GaAs and its intensity increases with a picosecond delay relative to the front of powerful picosecond optical pumping that produced a dense electron-hole plasma. The emission intensity relaxes with decreasing pumping with a characteristic time of {approx}10 ps. We have derived the dependences of the delay time, the relaxation time, and the duration of the picosecond emission pulse on its photon energy. The estimates based on the fact that the relaxation of emission is determined by electron-hole plasma cooling correspond to the measured relaxation time.

  11. Droplet destabilization during Bi catalyzed vapor-liquuid-solid growth of GaAs

    SciTech Connect (OSTI)

    DeJarld, M., E-mail: mdejarld@umich.edu; Nothern, D.; Millunchick, J. M. [Department of Materials Science and Engineering, University of Michigan 2300 Hayward Street, Ann Arbor, Michigan 48105 (United States)

    2014-03-21T23:59:59.000Z

    GaAs nanodiscs are grown in a molecular beam epitaxy chamber via the vapor-liquid-solid mechanism with liquid Bi as the catalyst. Each nanostructure consists of a series of increasingly larger overlapping discs. The structure forms during deposition due to the fact that the catalyst grows until reaching a critical size whereupon it destabilizes, dropping off the disc onto the substrate, where it catalyzes the growth of a new disc of larger radius. It is shown that critical size is limited by the sidewall wetting with a contact angle significantly smaller than the Gibb's criterion.

  12. Waveguide effect of GaAsSb quantum wells in a laser structure based on GaAs

    SciTech Connect (OSTI)

    Aleshkin, V. Ya. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)] [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Afonenko, A. A. [Belarussian State University (Belarus)] [Belarussian State University (Belarus); Dikareva, N. V. [Research Physical-Technical Institute of Nizhni Novgorod State University (Russian Federation)] [Research Physical-Technical Institute of Nizhni Novgorod State University (Russian Federation); Dubinov, A. A., E-mail: sanya@ipm.sci-nnov.ru; Kudryavtsev, K. E.; Morozov, S. V. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)] [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Nekorkin, S. M. [Research Physical-Technical Institute of Nizhni Novgorod State University (Russian Federation)] [Research Physical-Technical Institute of Nizhni Novgorod State University (Russian Federation)

    2013-11-15T23:59:59.000Z

    The waveguide effect of GaAsSb quantum wells in a semiconductor-laser structure based on GaAs is studied theoretically and experimentally. It is shown that quantum wells themselves can be used as waveguide layers in the laser structure. As the excitation-power density attains a value of 2 kW/cm{sup 2} at liquid-nitrogen temperature, superluminescence at the wavelength corresponding to the optical transition in bulk GaAs (at 835 nm) is observed.

  13. Deep level defects in proton radiated GaAs grown on metamorphic SiGe/Si substrates

    SciTech Connect (OSTI)

    Gonzalez, M.; Andre, C. L.; Walters, R. J.; Messenger, S. R.; Warner, J. H.; Lorentzen, J. R.; Pitera, A. J.; Fitzgerald, E. A.; Ringel, S. A. [Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio 43210 (United States); U.S. Naval Research Laboratory, Code 6818, Washington, DC 20375 (United States); Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio 43210 (United States)

    2006-08-01T23:59:59.000Z

    The effect of 2 MeV proton radiation on the introduction of deep levels in GaAs grown on compositionally graded SiGe/Si substrates was investigated using deep level transient spectroscopy (DLTS). Systematic comparisons were made with identical layers grown on both GaAs and Ge substrates to directly assess the influence of threading dislocations on radiation-related deep levels for both n-type and p-type GaAs. DLTS revealed that for p{sup +}n structures, proton irradiation generates electron traps at E{sub c}-0.14 eV, E{sub c}-0.25 eV, E{sub c}-0.54 eV, and E{sub c}-0.72 eV in the n-GaAs base, and, for n{sup +}p structures, radiation-induced hole traps appear at E{sub v}+0.18 eV, E{sub v}+0.23 eV, E{sub v}+0.27 eV, and E{sub v}+0.77 eV in the p-type GaAs base, irrespective of substrate choice for both polarities. The primary influence of substituting SiGe/Si substrates for conventional GaAs and Ge substrates is on the introduction rates of the individual traps as a function of proton radiation fluence. Substantially reduced concentrations are found for each radiation-induced hole trap observed in p-type GaAs, as well as for the E{sub c}-0.54 eV trap in n-GaAs for samples on SiGe/Si, as a function of proton fluence. Calculated trap introduction rates reveal reductions by as much as {approx}40% for certain hole traps in p-GaAs grown on SiGe/Si. This increased radiation tolerance for GaAs grown on SiGe/Si is attributed to interactions between the low density ({approx}10{sup 6} cm{sup -2}) of residual dislocations within the metamorphic GaAs/SiGe/Si structure and the radiation-induced point defects. Nevertheless, the fact that the impact of dislocations on radiation tolerance is far more dramatic for n{sup +}p GaAs structures compared to p{sup +}n structures, may have implications on future III-V/Si space solar cell design optimization, since end-of-life versus beginning-of-life differences are critical factors for power profiling in high radiation environments.

  14. Picosecond spin relaxation in low-temperature-grown GaAs

    SciTech Connect (OSTI)

    Uemura, M.; Honda, K.; Yasue, Y.; Tackeuchi, A., E-mail: atacke@waseda.jp [Department of Applied Physics, Waseda University, Tokyo 169-8555 (Japan); Lu, S. L.; Dai, P. [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Science, Suzhou (China)

    2014-03-24T23:59:59.000Z

    The spin relaxation process of low-temperature-grown GaAs is investigated by spin-dependent pump and probe reflectance measurements with a sub-picosecond time resolution. Two very short carrier lifetimes of 2.0 ps and 28 ps, which can be attributed to nonradiative recombinations related to defects, are observed at 10?K. The observed spin polarization shows double exponential decay with spin relaxation times of 46.2 ps (8.0 ps) and 509 ps (60 ps) at 10?K (200?K). The observed picosecond spin relaxation, which is considerably shorter than that of conventional GaAs, indicates the strong relevance of the Elliott-Yafet process as the spin relaxation mechanism. For the first (second) spin relaxation component, the temperature and carrier density dependences of the spin relaxation time indicate that the Bir-Aronov-Pikus process is also effective at temperatures between 10?K and 77?K, and that the D'yakonov-Perel’ process is effective between 125?K (77?K) and 200?K.

  15. Surface Science Analysis of GaAs Photocathodes Following Sustained Electron Beam Delivery

    SciTech Connect (OSTI)

    Shutthanandan, V.; Zhu, Zihua; Stutzman, Marcy L.; Hannon, Fay; Hernandez-Garcia, Carlos; Nandasiri, Manjula I.; Kuchibhatla, Satyanarayana V N T; Thevuthasan, Suntharampillai; Hess, Wayne P.

    2012-06-12T23:59:59.000Z

    Degradation of the photocathode materials employed in photoinjectors represents a challenge for sustained operation of nuclear physics accelerators and high power Free Electron Lasers (FEL). Several photocathode degradation processes are suspected, including defect formation by ion back bombardment, photochemistry of surface adsorbed species and irradiation-induced surface defect formation. To better understand the mechanisms of photocathode degradation, we have conducted surface and bulk analysis studies of two GaAs photocathodes removed from the FEL photoinjector after delivering electron beam for a few years. The analysis techniques include Helium Ion Microscopy (HIM), Rutherford Backscattering Spectrometry (RBS), Atomic Force Microscopy (AFM) and Secondary Ion Mass Spectrometry (SIMS). In addition, strained super-lattice GaAs photocathode samples, removed from the CEBAF photoinjector were analyzed using Transmission Electron Microscopy (TEM) and SIMS. This analysis of photocathode degradation during nominal photoinjector operating conditions represents first steps towards developing robust new photocathode designs necessary for generating sub-micron emittance electron beams required for both fourth generation light sources and intense polarized CW electron beams for nuclear and high energy physics facilities.

  16. Bistability of self-modulation of the GaAs intrinsic stimulated picosecond radiation spectrum

    SciTech Connect (OSTI)

    Ageeva, N. N.; Bronevoi, I. L., E-mail: bil@cplire.ru; Zabegaev, D. N.; Krivonosov, A. N. [Russian Academy of Sciences, Kotel'nikov Institute of Radio Engineering and Electronics (Russian Federation)] [Russian Academy of Sciences, Kotel'nikov Institute of Radio Engineering and Electronics (Russian Federation)

    2013-08-15T23:59:59.000Z

    The bistability of self-modulation of the spectrum of the stimulated picosecond radiation that appears during picosecond optical pumping of GaAs is detected. The radiation is measured before it reaches the end faces of a sample. One set of equidistant modes occurs in the radiation spectrum at the radiation pulse front. A set of modes located at the center between the initial modes replaces the first set in the descending radiation branch. The intermode interval inside each set coincides with the calculated interval between the eigenmodes of the GaAs layer, which is an active cavity. The radiation rise time turns out to be an oscillating function of the photon energy. The spectrum evolution is self-consistent so that the time-integrated spectrum and the spectrum-integrated radiation pulse envelope have a smooth (without local singularities) shape. The revealed bistability explains the physical nature of the two radiation-induced states of population depletion between which subterahertz self-oscillations in the radiation field were detected earlier. The radiation spectrum self-modulation is assumed to be a variant of stimulated Raman scattering.

  17. Effect of catalyst diameter on vapour-liquid-solid growth of GaAs nanowires

    SciTech Connect (OSTI)

    O'Dowd, B. J., E-mail: odowdbj@tcd.ie; Shvets, I. V. [CRANN, School of Physics, Trinity College, the University of Dublin, Dublin D2 (Ireland); Wojtowicz, T.; Kolkovsky, V.; Wojciechowski, T.; Zgirski, M. [Institute of Physics, Polish Academy of Sciences, Warsaw 02-668 (Poland); Rouvimov, S. [Notre Dame Integrated Imaging Facility (NDIIF), University of Notre Dame, Notre Dame, Indiana 46556 (United States); Liu, X.; Pimpinella, R.; Dobrowolska, M.; Furdyna, J. [Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 (United States)

    2014-08-14T23:59:59.000Z

    GaAs nanowires were grown on (111)B GaAs substrates using the vapour-liquid-solid mechanism. The Au/Pt nanodots used to catalyse wire growth were defined lithographically and had varying diameter and separation. An in-depth statistical analysis of the resulting nanowires, which had a cone-like shape, was carried out. This revealed that there were two categories of nanowire present, with differing height and tapering angle. The bimodal nature of wire shape was found to depend critically on the diameter of the Au-Ga droplet atop the nanowire. Transmission electron microscopy analysis also revealed that the density of stacking faults in the wires varied considerably between the two categories of wire. It is believed that the cause of the distinction in terms of shape and crystal structure is related to the contact angle between the droplet and the solid-liquid interface. The dependency of droplet diameter on contact angle is likely related to line-tension, which is a correction to Young's equation for the contact angle of a droplet upon a surface. The fact that contact angle may influence resulting wire structure and shape has important implications for the planning of growth conditions and the preparation of wires for use in proposed devices.

  18. Large-Signal HBT Model with Improved Collector Transit Time Formulation for GaAs and InP Technologies

    E-Print Network [OSTI]

    Asbeck, Peter M.

    mi': iaE Large-Signal HBT Model with Improved Collector Transit Time Formulation for GaAs and In large-signal HBT model which accurately accounts for the intricate hias dependence of collector delay collector delay function accounts for the variation of electron velocity with electric field

  19. X-ray imaging and diffraction from surface phonons on GaAs W. Sauer,a)

    E-Print Network [OSTI]

    Ludwig-Maximilians-Universität, München

    , the driver frequency of the synchrotron was multiplied 102 times by a phase-locked loop PLL , ampli- fied are excited on the GaAs 001 surface by using interdigital transducers, designed for frequencies of up to 900 to measured diffraction profiles at different excitation voltages, the SAW amplitudes were calculated

  20. Femtosecond-scale response of GaAs to ultrafast laser pulses Traian Dumitrica* and Roland E. Allen

    E-Print Network [OSTI]

    Allen, Roland E.

    Femtosecond-scale response of GaAs to ultrafast laser pulses Traian Dumitrica* and Roland E. Allen ordinary heating of the sample by phonon emission, there is convinc- ing evidence that ultrafast pulses of the initial stages of the interaction of a laser pulse with a semiconductor, which show that ultrafast disor

  1. All-optical generation and detection of subpicosecond ac spin-current pulses in GaAs

    E-Print Network [OSTI]

    Ruzicka, Brian Andrew; Higley, Karl; Werake, Lalani Kumari; Zhao, Hui

    2008-07-01T23:59:59.000Z

    Subpicosecond ac spin-current pulses are generated optically in GaAs bulk and quantum wells at room temperature and at 90 K through quantum interference between one-photon and two-photon absorptions driven by two phase-locked ultrafast laser pulses...

  2. Ultrafast (370 GHz bandwidth) p-i-n traveling wave photodetector using low-temperature-grown GaAs

    E-Print Network [OSTI]

    Bowers, John

    measured with a thermocouple temperature sensor and then in situ annealed at 590 °C for 10 min. We found photodetectors utilizing low-temperature-grown GaAs as the absorption layer. The electro-optically measured-efficiency product. By dis- tributing the RC elements and impedance matching to exter- nal circuits, both p

  3. Diffusion of a Ga adatom on the GaAs(001)c(44)heterodimer surface: A first principles study

    E-Print Network [OSTI]

    Khare, Sanjay V.

    Diffusion of a Ga adatom on the GaAs(001)c(4×4)heterodimer surface: A first principles study J Diffusion barriers Reconstruction Density functional calculations The adsorption and diffusion behavior functional theory (DFT) computations in the local density approxima- tion. Structural and bonding features

  4. I-V analysis of high-energy lithium-ion-irradiated Si and GaAs solar cells

    E-Print Network [OSTI]

    A. Meulenberg Jr; B. Jayashree; Ramani; M. C. Radhakrishna; A. K. Saif

    2007-09-07T23:59:59.000Z

    Space-grade Si and GaAs solar cells were irradiated with 15 and 40 MeV lithium ions. Dark-IV analysis (with and without illumination) reveals differences in the effects of such irradiation on the different cell types

  5. THIN FILM SOLAR CELLS AND A REVIEW OF RECENT RESULTS ON GaAs By PAUL RAPPAPORT,

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    154. THIN FILM SOLAR CELLS AND A REVIEW OF RECENT RESULTS ON GaAs By PAUL RAPPAPORT, RCA PHYSIQUE APPLIQUÃ?E TOME 1, SEPTEMBRE 1966, PAGE ' Two of the most urgent requirements of future solar cells are lower cost and lighter weight. Pre- sent cost of solar cells is in the s 200 to $ 400/watt range, which

  6. Material and device characterization toward high-efficiency GaAs solar cells on optical-grade polycrystalline Ge substrates

    SciTech Connect (OSTI)

    Venkatasubramanian, R.; Malta, D.P.; Timmons, M.L.; Posthill, J.B.; Hutchby, J.A. [Research Triangle Inst., Research Triangle Park, NC (United States); Ahrenkiel, R.; Keyes, B.; Wangensteen, T. [National Renewable Energy Lab., Golden, CO (United States)

    1994-12-31T23:59:59.000Z

    In this work, the authors present a detailed characterization of the material and device properties of GaAs materials grown on optical-grade poly-Ge substrates. Although the minority-carrier lifetime of the starting optical-grade polycrystalline Ge substrate is about a factor of 8 less than that measured in single-crystal electronic-grade Ge, the minority carrier lifetime in GaAs-AlGaAs double-hetero (DH) structures grown on these two substrates were about comparable. C-V measurements on poly-GaAs p{sup +}n junctions indicate negligible role of grain-boundaries in majority-carrier trapping and also that no compensating deep levels were introduced into the n-GaAs active layers from the optical-grade substrates. The polycrystalline GaAs p{sup +}-n junctions were evaluated by dark In I-V measurements and the authors observed that there is a considerable variation of the saturation dark current density (within a factor of ten) of diodes located in various grains. The performance of the poly p{sup +}n GaAs cells is improved by the introduction of an undoped spacer in the p{sup +}-n junction. Diode I-V data of p{sup +}-n GaAs junctions, grown with this spacer, show a factor of near 100 reduction in diode saturation dark-current density. The reduction in dark current is believed to be associated with the reduction of tunneling currents in the depletion-layer of the p{sup +}-n junction in polycrystalline materials. Since the series resistance of the lightly-doped substrate is presently limiting the efficiency of large-area cells, efforts are underway to develop GaAs solar cells on more heavily-doped poly-Ge substrates.

  7. National Gypsum | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page onYou are now leaving Energy.gov You are now leaving Energy.gov You are beingZealand Jump to: navigation, searchOfRose BendMiasoleTremor(Question)8/14/2007NCPV Jump to:Management

  8. Fano Resonance in GaAs 2D Photonic Crystal Nanocavities

    SciTech Connect (OSTI)

    Valentim, P. T.; Guimaraes, P.S. S. [Departamento de Fisica, Universidade Federal de Minas Gerais, Belo Horizonte (Brazil); Instituto Nacional de Ciencia e Tecnologia de Nanodispositivos Semicondutores - INCT-DISSE (Brazil); Luxmoore, I. J.; Szymanski, D.; Whittaker, D. M.; Fox, A. M.; Skolnick, M. S. [Department of Physics and Astronomy, University of Sheffield, Sheffield (United Kingdom); Vasco, J. P. [Instituto de Fisica, Universidad de Antioquia, Medellin (Colombia); Vinck-Posada, H. [Departamento de Fisica, Facultad de Ciencias, Universidad Nacional de Colombia, Bogota (Colombia)

    2011-12-23T23:59:59.000Z

    We report the results of polarization resolved reflectivity experiments in GaAs air-bridge photonic crystals with L3 cavities. We show that the fundamental L3 cavity mode changes, in a controlled way, from a Lorentzian symmetrical lineshape to an asymmetrical form when the linear polarization of the incident light is rotated in the plane of the crystal. The different lineshapes are well fitted by the Fano asymmetric equation, implying that a Fano resonance is present in the reflectivity. We use the scattering matrix method to model the Fano interference between a localized discrete state (the cavity fundamental mode) and a background of continuum states (the light reflected from the crystal slab in the vicinity of the cavity) with very good agreement with the experimental data.

  9. Real-time reflectance-difference spectroscopy of GaAs molecular beam epitaxy homoepitaxial growth

    SciTech Connect (OSTI)

    Lastras-Martínez, A., E-mail: alm@cactus.iico.uaslp.mx, E-mail: alastras@gmail.com; Ortega-Gallegos, J.; Guevara-Macías, L. E.; Nuñez-Olvera, O.; Balderas-Navarro, R. E.; Lastras-Martínez, L. F. [Instituto de Investigación en Comunicación Optica, Universidad Autónoma de San Luis Potosí, Alvaro Obregón 64, San Luis Potosí, SLP 78000 (Mexico); Lastras-Montaño, L. A. [IBM T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Lastras-Montaño, M. A. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, Santa Barbara, California 93106 (United States)

    2014-03-01T23:59:59.000Z

    We report on real time-resolved Reflectance-difference (RD) spectroscopy of GaAs(001) grown by molecular beam epitaxy, with a time-resolution of 500 ms per spectrum within the 2.3–4.0 eV photon energy range. Through the analysis of transient RD spectra we demonstrated that RD line shapes are comprised of two components with different physical origins and determined their evolution during growth. Such components were ascribed to the subsurface strain induced by surface reconstruction and to surface stoichiometry. Results reported in this paper render RD spectroscopy as a powerful tool for the study of fundamental processes during the epitaxial growth of zincblende semiconductors.

  10. High quality molecular beam epitaxial growth on patterned GaAs substrates

    SciTech Connect (OSTI)

    Smith, J.S.; Derry, P.L.; Margalit, S.; Yariv, A.

    1985-10-01T23:59:59.000Z

    In this letter we describe a procedure for high quality molecular beam epitaxy (MBE) growth over finely patterned GaAs substrates which is suitable for device fabrication requiring lateral definition of small (approx.1--2 ..mu..m) dimension. This method was used for the fabrication of index guided laser arrays. Yields of individual lasers exceeded 90%, and thresholds were uniform to 10%. Temperature and flux ratio dependence of faceting during MBE growth over patterned substrates is shown for temperatures ranging from 580 to 700 /sup 0/C and for As/Ga flux ratios from 1.4:1 to 4:1. The real index guided structure, which can be formed by a single MBE growth over a ridged substrate, is discussed. This technique should prove useful in the fabrication of devices which take advantage of unique features formed during regrowth by MBE.

  11. Charge tuning in [111] grown GaAs droplet quantum dots

    SciTech Connect (OSTI)

    Bouet, L.; Vidal, M.; Marie, X.; Amand, T.; Wang, G.; Urbaszek, B. [INSA-CNRS-UPS, LPCNO, Université de Toulouse, 135 Ave. Rangueil, 31077 Toulouse (France); Mano, T.; Ha, N.; Kuroda, T.; Sakoda, K. [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan); Durnev, M. V.; Glazov, M. M.; Ivchenko, E. L. [Ioffe Physical-Technical Institute RAS, 194021 St.-Petersburg (Russian Federation)

    2014-08-25T23:59:59.000Z

    We demonstrate charge tuning in strain free GaAs/AlGaAs quantum dots (QDs) grown by droplet epitaxy on a GaAs(111)A substrate. Application of a bias voltage allows the controlled charging of the QDs from ?3|e| to +2|e|. The resulting changes in QD emission energy and exciton fine-structure are recorded in micro-photoluminescence experiments at T?=?4?K. We uncover the existence of excited valence and conduction states, in addition to the s-shell-like ground state. We record a second series of emission lines about 25?meV above the charged exciton emission coming from excited charged excitons. For these excited interband transitions, a negative diamagnetic shift of large amplitude is uncovered in longitudinal magnetic fields.

  12. Photoluminescence of GaAs films grown by vacuum chemical epitaxy

    SciTech Connect (OSTI)

    Bernussi, A.A.; Barreto, C.L.; Carvalho, M.M.G.; Motisuke, P.

    1988-08-01T23:59:59.000Z

    GaAs layers grown by vacuum chemical epitaxy (VCE) are investigated by low-temperature photoluminescence. A qualitative relation between the growth parameters and the shallow-impurity-incorporation mechanism is established. It was observed that the predominant shallow acceptor is carbon, and its incorporation during the growth process decreases with the As:Ga ratio, increases with growth temperature until 750 /sup 0/C, and then it diminishes. In this work we compare the characteristics observed in the VCE system with those in conventional molecular-beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD). Our results show that this system contains some advantages from both the MBE and MOCVD systems. The photoluminescence spectra also show that at low As:Ga ratios the generation of As vacancies or its complexes is strongly enhanced.

  13. Molecular-beam epitaxial growth of boron-doped GaAs films

    SciTech Connect (OSTI)

    Hoke, W.E.; Lemonias, P.J.; Weir, D.G. [Raytheon Research Division, Lexington, MA (United States)] [and others] [Raytheon Research Division, Lexington, MA (United States); and others

    1993-05-01T23:59:59.000Z

    GaAs films doped with boron in the 10{sup 20} cm{sup {minus}3} range were grown by solid source molecular-beam epitaxy. Lattice contractions were observed in x-ray double crystal spectra. Substitutional boron concentrations up to 1.7x10{sup 20} cm{sup {minus}3} were obtained with narrow x-ray linewidths and specular surface morphology. For a given boron flux, the substitutional concentration was dependent on growth temperature. P-type conductivity due to boron incorporation was measured in the films with hole concentration reaching 1x10{sup 19} cm{sup {minus}3}. The lattice contractions exhibited good thermal stability for rapid thermal anneals. 10 refs., 3 figs., 2 tabs.

  14. Evolution of superclusters and delocalized states in GaAs1–xNx

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Fluegel, B.; Alberi, K.; Beaton, D. A.; Crooker, S. A.; Ptak, A. J.; Mascarenhas, A.

    2012-11-01T23:59:59.000Z

    The evolution of individual nitrogen cluster bound states into an extended state infinite supercluster in dilute GaAs1–xNx was probed through temperature and intensity-dependent, time-resolved and magnetophotoluminescence (PL) measurements. Samples with compositions less than 0.23% N exhibit PL behavior that is consistent with emission from the extended states of the conduction band. Near a composition of 0.23% N, a discontinuity develops between the extended state PL peak energy and the photoluminescence excitation absorption edge. The existence of dual localized/delocalized state behavior near this composition signals the formation of an N supercluster just below the conduction band edge. The infinite supercluster is fully developed by 0.32% N.

  15. Epitaxial lift-off of quantum dot enhanced GaAs single junction solar cells

    SciTech Connect (OSTI)

    Bennett, Mitchell F.; Bittner, Zachary S.; Forbes, David V.; Hubbard, Seth M., E-mail: smhsps@rit.edu [Rochester Institute of Technology, Rochester, New York 14623 (United States); Rao Tatavarti, Sudersena; Wibowo, Andree; Pan, Noren; Chern, Kevin [MicroLink Devices, Inc., Niles, Illinois 60714 (United States)] [MicroLink Devices, Inc., Niles, Illinois 60714 (United States); Phillip Ahrenkiel, S. [South Dakota School of Mines and Technology, Rapid City, South Dakota 57701 (United States)] [South Dakota School of Mines and Technology, Rapid City, South Dakota 57701 (United States)

    2013-11-18T23:59:59.000Z

    InAs/GaAs strain-balanced quantum dot (QD) n-i-p solar cells were fabricated by epitaxial lift-off (ELO), creating thin and flexible devices that exhibit an enhanced sub-GaAs bandgap current collection extending into the near infrared. Materials and optical analysis indicates that QD quality after ELO processing is preserved, which is supported by transmission electron microscopy images of the QD superlattice post-ELO. Spectral responsivity measurements depict a broadband resonant cavity enhancement past the GaAs bandedge, which is due to the thinning of the device. Integrated external quantum efficiency shows a QD contribution to the short circuit current density of 0.23?mA/cm{sup 2}.

  16. Measurement of electron beam polarization from unstrained GaAs via two-photon photoemission

    SciTech Connect (OSTI)

    McCarter, James L. [Univ. of Virginia, Charlottesville, VA (United States); Afanasev, A. [George Washington Univ., Washingon, DC (United States); Gay, T. J. [Univ. of Nebraska, Lincoln, NE (United States); Hansknecht, John C. [JLAB, Newport News, VA (United States); Kechiantz, A. [George Washington Univ., Washingon, DC (United States); Poelker, B. Matthew [JLAB, Newport News, VA (United States)

    2014-02-01T23:59:59.000Z

    Two-photon absorption of 1560 nm light was used to generate polarized electron beams from unstrained GaAs photocathodes of varying thickness: 625 {mu}m, 0.32 {mu}m, and 0.18 {mu}m. For each photocathode, the degree of spin polarization of the photoemitted beam was less than 50%, contradicting earlier predictions based on simple quantum mechanical selection rules for spherically-symmetric systems but consistent with the more sophisticated model of Bhat et al. (Phys. Rev. B 71 (2005) 035209). Polarization via two-photon absorption was the highest from the thinnest photocathode sample and comparable to that obtained via one-photon absorption (using 778 nm light), with values 40.3 +- 1.0% and 42.6 +- 1.0%, respectively.

  17. High quality metamorphic graded buffers with lattice-constants intermediate to GaAs an InP for device applications

    E-Print Network [OSTI]

    Lee, Kenneth Eng Kian

    2009-01-01T23:59:59.000Z

    We have investigated the use of a continuous, linear grading scheme for compositionally-graded metamorphic InxGal-As buffers on GaAs, which can be used as virtual substrates for optical emitters operating at wavelengths > ...

  18. Energy distribution of nonequilibrium electrons and optical phonons in GaAs under band-to-band pumping by intense short pulses of light

    SciTech Connect (OSTI)

    Altybaev, G. S.; Kumekov, S. E., E-mail: skumekov@mail.ru; Mahmudov, A. A. [Satpaev Kazakh National Technical University (Kazakhstan)

    2009-03-15T23:59:59.000Z

    Deviation from the Fermi distribution of nonequilibrium electrons and distribution of 'hot' optical phonons in GaAs under band-to-band pumping by picosecond pulses of light are calculated.

  19. Simulation of quantum dots size and spacing effect for intermediate band solar cell application based on InAs quantum dots arrangement in GaAs

    SciTech Connect (OSTI)

    Hendra, P. I. B., E-mail: ib.hendra@gmail.com; Rahayu, F., E-mail: ib.hendra@gmail.com; Darma, Y., E-mail: ib.hendra@gmail.com [Physical Vapor Deposition Laboratory, Physics of Material Electronics Research, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132 (Indonesia)

    2014-03-24T23:59:59.000Z

    Intermediate band solar cell (IBSC) has become a promising technology in increasing solar cell efficiency. In this work we compare absorption coefficient profile between InAs quantum dots with GaAs bulk. We calculate the efficiency of GaAs bulk and GaAs doped with 2, 5, and 10 nm InAs quantum dot. Effective distances in quantum dot arrangement based on electron tunneling consideration were also calculated. We presented a simple calculation method with low computing power demand. Results showed that arrangement of quantum dot InAs in GaAs can increase solar cell efficiency from 23.9 % initially up to 60.4%. The effective distance between two quantum dots was found 2 nm in order to give adequate distance to prevent electron tunneling and wave functions overlap.

  20. Piezoelectric surface acoustical phonon amplification in graphene on a GaAs substrate

    SciTech Connect (OSTI)

    Nunes, O. A. C., E-mail: oacn@unb.br [Institute of Physics, University of Brasilia, Brasilia, 70910-900 DF (Brazil)

    2014-06-21T23:59:59.000Z

    We study the interaction of Dirac Fermions in monolayer graphene on a GaAs substrate in an applied electric field by the combined action of the extrinsic potential of piezoelectric surface acoustical phonons of GaAs (piezoelectric acoustical (PA)) and of the intrinsic deformation potential of acoustical phonons in graphene (deformation acoustical (DA)). We find that provided the dc field exceeds a threshold value, emission of piezoelectric (PA) and deformation (DA) acoustical phonons can be obtained in a wide frequency range up to terahertz at low and high temperatures. We found that the phonon amplification rate R{sup PA,DA} scales with T{sub BG}{sup S?1} (S=PA,DA), T{sub BG}{sup S} being the Block?Gru{sup ¨}neisen temperature. In the high-T Block?Gru{sup ¨}neisen regime, extrinsic PA phonon scattering is suppressed by intrinsic DA phonon scattering, where the ratio R{sup PA}/R{sup DA} scales with ?1/?(n), n being the carrier concentration. We found that only for carrier concentration n?10{sup 10}cm{sup ?2}, R{sup PA}/R{sup DA}>1. In the low-T Block?Gru{sup ¨}neisen regime, and for n=10{sup 10}cm{sup ?2}, the ratio R{sup PA}/R{sup DA} scales with T{sub BG}{sup DA}/T{sub BG}{sup PA}?7.5 and R{sup PA}/R{sup DA}>1. In this regime, PA phonon dominates the electron scattering and R{sup PA}/R{sup DA}<1 otherwise. This study is relevant to the exploration of the acoustic properties of graphene and to the application of graphene as an acoustical phonon amplifier and a frequency-tunable acoustical phonon device.

  1. Highly uniform, multi-stacked InGaAs/GaAs quantum dots embedded in a GaAs nanowire

    SciTech Connect (OSTI)

    Tatebayashi, J., E-mail: tatebaya@iis.u-tokyo.ac.jp; Ota, Y. [NanoQUINE, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Ishida, S.; Nishioka, M.; Iwamoto, S.; Arakawa, Y. [NanoQUINE, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Institute of Industrial Science, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

    2014-09-08T23:59:59.000Z

    We demonstrate a highly uniform, dense stack of In{sub 0.22}Ga{sub 0.78}As/GaAs quantum dot (QD) structures in a single GaAs nanowire (NW). The size (and hence emission energy) of individual QD is tuned by careful control of the growth conditions based on a diffusion model of morphological evolution of NWs and optical characterization. By carefully tailoring the emission energies of individual QD, dot-to-dot inhomogeneous broadening of QD stacks in a single NW can be as narrow as 9.3?meV. This method provides huge advantages over traditional QD stack using a strain-induced Stranski-Krastanow growth scheme. We show that it is possible to fabricate up to 200 uniform QDs in single GaAs NWs using this growth technique without degradation of the photoluminescence intensity.

  2. Atomic-scale observation of parallel development of super elasticity and reversible plasticity in GaAs nanowires

    SciTech Connect (OSTI)

    Bao, Peite; Du, Sichao; Zheng, Rongkun, E-mail: rongkun.zheng@sydney.edu.au [School of Physics, The University of Sydney, Sydney, NSW 2006 (Australia); Wang, Yanbo; Liao, Xiaozhou, E-mail: xiaozhou.liao@sydney.edu.au [School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, NSW 2006 (Australia); Cui, Xiangyuan; Yen, Hung-Wei; Kong Yeoh, Wai; Ringer, Simon P. [School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, NSW 2006 (Australia); Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006 (Australia); Gao, Qiang; Hoe Tan, H.; Jagadish, Chennupati [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia); Liu, Hongwei [Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006 (Australia); Zou, Jin [Materials Engineering and Centre for Microscopy and Microanalysis, The University of Queensland, Brisbane, QLD 4072 (Australia)

    2014-01-13T23:59:59.000Z

    We report the atomic-scale observation of parallel development of super elasticity and reversible dislocation-based plasticity from an early stage of bending deformation until fracture in GaAs nanowires. While this phenomenon is in sharp contrast to the textbook knowledge, it is expected to occur widely in nanostructures. This work indicates that the super recoverable deformation in nanomaterials is not simple elastic or reversible plastic deformation in nature, but the coupling of both.

  3. Influence of uniaxial pressure on the critical temperature for long delays in GaAs junction lasers

    SciTech Connect (OSTI)

    Morosini, M.B.Z.; Patel, N.B.; Nunes, F.D.

    1980-09-01T23:59:59.000Z

    In this work we report on the influence of uniaxial pressure applied perpendicularly to junction laser on the behavior of the critical temperature for the onset of long delays in GaAs junction lasers. Experimental data showing this influence for lasers operating in a TE or TM polarization are presented and explained on the basis of a thermal theory of long delays and related phenomena.

  4. Cryogenic on-wafer microwave characterization of GaAs MESFETs and superconducting coplanar resonance and transmission lines structures

    SciTech Connect (OSTI)

    Kruse, J.; Schweinfurth, R.A.; Gao, F.; Scherrer, D.; Barlage, D.; Platt, C.E.; Van Harlingen, D.J.; Feng, M. [Univ. of Illinois, Urbana, IL (United States)

    1994-12-31T23:59:59.000Z

    This work directly compares coplanar superconducting transmission lines and single-pole resonators patterned from YBCO to aluminum structures for use in GaAs/YBCO hybrid circuitry. A cryogenic on-wafer station was used to make s-parameter measurements of passive coplanar circuits as well as to characterize the performance of GaAs MESFETs at 80K. Comparisons were made between measured data and theoretical results for passive YBCO and Aluminum structures. The YBCO film was also measured using a parallel plate technique to determine microwave surface resistance to establish a correlation between patterned film and thin film microwave properties. Small-signal models were constructed to accurately predict the operation of 0.25{mu}m gate length GaAs MESFETs at 80 K under a variety of bias conditions. The cutoff frequency and maximum frequency of operation of the GaAs MESFETs increased by 29% and 13% respectively under a drain-source voltage of 2.0 V (Id = 100%Idss) as the temperature was lowered from 300K to 80K.

  5. dc field-emission analysis of GaAs and plasma-source ion-implanted stainless steel

    SciTech Connect (OSTI)

    C. Hernandez; T. Wang; T. Siggins; D. Bullard; H. F. Dylla; C. Reece; N. D. Theodore; D. M. Manos

    2003-06-01T23:59:59.000Z

    Field-emission studies have been performed on a GaAs wafer and a sample of its stainless-steel (SS) support electrode that are part of a photocathode gun for the 10 kW Upgrade infrared free electron laser at Jefferson Lab. The objective of the studies presented here is to characterize the effect of both the cleanliness of the wafer and the plasma-source ion-implanted layer on the electrode to suppress field emission. Field emission is the limiting factor to achieve the required 6 MV/m at the surface of the wafer. Potential field emitters are first located on the surface of 1 in. diameter samples with a dc scanning field-emission microscope at 60 MV/m, then each emitter is characterized in a scanning electron microscope equipped with an energy dispersive spectrometer. The GaAs wafer was hydrogen cleaned before the study. The results show three emitters caused by indium contamination during wafer handling. The GaAs wafer thus shows good high-voltage characteristics and the need to maintain cleanliness during handling. The SS sample is hand polished with diamond paste to a 1-m surface finish, then implanted with N2/SiO2 in a plasma-source ion-implantation chamber in preparation for the field-emission studies.

  6. Velocity distribution function of sputtered gallium atoms during inductively coupled argon plasma treatment of a GaAs surface

    SciTech Connect (OSTI)

    Despiau-Pujo, Emilie; Chabert, Pascal; Ramos, Raphaeel; Cunge, Gilles; Sadeghi, Nader [Laboratoire de Physique des Plasmas, Ecole Polytechnique, 91128 Palaiseau (France); Laboratoire des Technologies de la Microelectronique, CNRS, 38054 Grenoble (France)

    2009-03-15T23:59:59.000Z

    A GaN laser diode at 403.3 nm is used to measure the velocity distribution function (vdf) of Ga atoms sputtered from a radio-frequency biased GaAs substrate in a low pressure inductively coupled plasma (ICP) argon discharge. To investigate both perpendicular (V{sub z} normal to wafer) and longitudinal (V{sub x} parallel to wafer) velocity components, laser induced fluorescence (LIF) measurements are performed in the z direction and atomic absorption spectroscopy (AAS) in the x direction. The longitudinal vdf of Ga sputtered atoms is very close to a Lorentzian function with V{sub x} comprised between 0 and 7500 m s{sup -1}, while the perpendicular velocities V{sub z} can reach 10 000 m s{sup -1}. Experimental results are compared to molecular dynamics (MD) simulations of Ar{sup +} ion sputtering of GaAs under 200 eV bombardment. MD predictions and experiments are in fairly good agreement, which confirms the existence of products sputtered from the surface with kinetic energies larger than 10 eV. In etching processes dominated by physical bombardment, these energetic atoms could alter passivation layers on sidewalls and be responsible for defects observed in nanodevices. The best fit of the Doppler-broadened LIF and AAS profiles with the vdfs predicted by sputtering theory allows one to estimate the surface binding energy of Ga atoms in GaAs, E{sub b}, to be around 3 eV.

  7. X-ray pump optical probe cross-correlation study of GaAs

    SciTech Connect (OSTI)

    Durbin, S.M.; Clevenger, T.; Graber, T.; Henning, R. (Purdue); (UC)

    2012-09-10T23:59:59.000Z

    Ultrafast dynamics in atomic, molecular and condensed-matter systems are increasingly being studied using optical-pump, X-ray probe techniques where subpicosecond laser pulses excite the system and X-rays detect changes in absorption spectra and local atomic structure. New opportunities are appearing as a result of improved synchrotron capabilities and the advent of X-ray free-electron lasers. These source improvements also allow for the reverse measurement: X-ray pump followed by optical probe. We describe here how an X-ray pump beam transforms a thin GaAs specimen from a strong absorber into a nearly transparent window in less than 100 ps, for laser photon energies just above the bandgap. We find the opposite effect - X-ray induced optical opacity - for photon energies just below the bandgap. This raises interesting questions about the ultrafast many-body response of semiconductors to X-ray absorption, and provides a new approach for an X-ray/optical cross-correlator for synchrotron and X-ray free-electron laser applications.

  8. Thermal influence on charge carrier transport in solar cells based on GaAs PN junctions

    SciTech Connect (OSTI)

    Osses-Márquez, Juan; Calderón-Muñoz, Williams R., E-mail: wicalder@ing.uchile.cl [Department of Mechanical Engineering, University of Chile, Beauchef 850, Santiago (Chile)

    2014-10-21T23:59:59.000Z

    The electron and hole one-dimensional transport in a solar cell based on a Gallium Arsenide (GaAs) PN junction and its dependency with electron and lattice temperatures are studied here. Electrons and heat transport are treated on an equal footing, and a cell operating at high temperatures using concentrators is considered. The equations of a two-temperature hydrodynamic model are written in terms of asymptotic expansions for the dependent variables with the electron Reynolds number as a perturbation parameter. The dependency of the electron and hole densities through the junction with the temperature is analyzed solving the steady-state model at low Reynolds numbers. Lattice temperature distribution throughout the device is obtained considering the change of kinetic energy of electrons due to interactions with the lattice and heat absorbed from sunlight. In terms of performance, higher values of power output are obtained with low lattice temperature and hot energy carriers. This modeling contributes to improve the design of heat exchange devices and thermal management strategies in photovoltaic technologies.

  9. Thermal stability of TaSi/sub x/-GaAs Schottky barriers in rapid thermal processing. [Self-aligned gate fabrication of GaAs MESFETs

    SciTech Connect (OSTI)

    Haynes, T.E.; Han, C.C.; Lau, S.S.; Picraux, S.T.; Chu, W.K.

    1987-01-01T23:59:59.000Z

    Co-sputtered TaSi/sub x/ films on GaAs have been examined as potential refractory Schottky barrier contacts suitable for self-aligned gate fabrication of GaAs MESFETs. Thermal stability of electrical and physical characteristics has been studied following furnace annealing and rapid thermal processing of contacts with compositions near Ta/sub 5/Si/sub 3/ (x = 0.6). Assessment of integrity of the annealed contacts has been made based on measurement of electrical characteristics, interface interdiffusion, and evaporation of GaAs through the contact. Superior stability as a function of anneal temperature up to 900/sup 0/C was achieved for TaSi/sub 0.6/ contacts using rapid thermal processing (RTP) techniques rather than furnace annealing. Current-voltage characteristics were found to be insensitive to RTP temperature between 700 and 900/sup 0/C.

  10. Growth of high-quality GaAs on Ge/Si{sub 1-x}Ge{sub x} on nanostructured silicon substrates

    SciTech Connect (OSTI)

    Vanamu, G.; Datye, A.K.; Dawson, R.; Zaidi, Saleem H. [Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, New Mexico 87131 (United States) and Center for Micro-Engineered Materials, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Center for High Technology Materials, 1313 Goddard SE, Albuquerque, New Mexico 87106 (United States); Gratings, Inc., 2700 B Broadbent Parkway, NE, Albuquerque, New Mexico 87107 (United States)

    2006-06-19T23:59:59.000Z

    Heteroepitaxial growth of GaAs/Ge/SiGe films on submicrostructured Si substrates is reported. One-dimensional, nanometer-linewidth, submicrometer period features were fabricated in Si substrates using interferometric lithography, reactive ion etching, and wet-chemical etching techniques. The quality of the GaAs layers grown on these structures was investigated using high-resolution x-ray diffraction, transmission electron microscopy, scanning electron microscopy, photoluminescence, and etch pit density measurements. The defect density of GaAs epilayers grown on submicrostructured Si at {approx}6x10{sup 5} cm{sup -2} was two orders of magnitude lower compared with that grown on planar silicon. The optical quality of the GaAs/Ge/SiGe on submicrostructured Si was comparable to that of single crystal GaAs.

  11. Multi-junction, monolithic solar cell using low-band-gap materials lattice matched to GaAs or Ge

    DOE Patents [OSTI]

    Olson, Jerry M. (Lakewood, CO); Kurtz, Sarah R. (Golden, CO); Friedman, Daniel J. (Lakewood, CO)

    2001-01-01T23:59:59.000Z

    A multi-junction, monolithic, photovoltaic solar cell device is provided for converting solar radiation to photocurrent and photovoltage with improved efficiency. The solar cell device comprises a plurality of semiconductor cells, i.e., active p/n junctions, connected in tandem and deposited on a substrate fabricated from GaAs or Ge. To increase efficiency, each semiconductor cell is fabricated from a crystalline material with a lattice constant substantially equivalent to the lattice constant of the substrate material. Additionally, the semiconductor cells are selected with appropriate band gaps to efficiently create photovoltage from a larger portion of the solar spectrum. In this regard, one semiconductor cell in each embodiment of the solar cell device has a band gap between that of Ge and GaAs. To achieve desired band gaps and lattice constants, the semiconductor cells may be fabricated from a number of materials including Ge, GaInP, GaAs, GaInAsP, GaInAsN, GaAsGe, BGaInAs, (GaAs)Ge, CuInSSe, CuAsSSe, and GaInAsNP. To further increase efficiency, the thickness of each semiconductor cell is controlled to match the photocurrent generated in each cell. To facilitate photocurrent flow, a plurality of tunnel junctions of low-resistivity material are included between each adjacent semiconductor cell. The conductivity or direction of photocurrent in the solar cell device may be selected by controlling the specific p-type or n-type characteristics for each active junction.

  12. Impact of heavy hole-light hole coupling on optical selection rules in GaAs quantum dots

    SciTech Connect (OSTI)

    Belhadj, T.; Amand, T.; Kunz, S.; Marie, X.; Urbaszek, B. [INSA-CNRS-UPS, LPCNO, Universite de Toulouse, 135 Av. Rangueil, 31077 Toulouse (France); Kunold, A. [INSA-CNRS-UPS, LPCNO, Universite de Toulouse, 135 Av. Rangueil, 31077 Toulouse (France); Departamento de Ciencias Basicas, UAM-A, Col. Reynosa Tamaulipas, 02200 Mexico D.F. (Mexico); Simon, C.-M. [INSA-CNRS-UPS, LPCNO, Universite de Toulouse, 135 Av. Rangueil, 31077 Toulouse (France); CNRS-UPS, LCAR, IRSAMC, Universite de Toulouse, 31062 Toulouse (France); Kuroda, T.; Abbarchi, M.; Mano, T.; Sakoda, K. [National Institute for Material Science, Namiki 1-1, Tsukuba 305-0044 (Japan)

    2010-08-02T23:59:59.000Z

    We report strong heavy hole-light hole mixing in GaAs quantum dots grown by droplet epitaxy. Using the neutral and charged exciton emission as a monitor we observe the direct consequence of quantum dot symmetry reduction in this strain free system. By fitting the polar diagram of the emission with simple analytical expressions obtained from k{center_dot}p theory we are able to extract the mixing that arises from the heavy-light hole coupling due to the geometrical asymmetry of the quantum dot.

  13. Below gap optical absorption in GaAs driven by intense, single-cycle coherent transition radiation

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Goodfellow, J.; Fuchs, M.; Daranciang, D.; Ghimire, S.; Chen, F.; Loos, H.; Reis, D. A.; Fisher, A. S.; Lindenberg, A. M.

    2014-01-01T23:59:59.000Z

    Single-cycle terahertz fields generated by coherent transition radiation from a relativistic electron beam are used to study the high field optical response of single crystal GaAs. Large amplitude changes in the sub-band-gap optical absorption are induced and probed dynamically by measuring the absorption of a broad-band optical beam generated by transition radiation from the same electron bunch, providing an absolutely synchronized pump and probe geometry. This modification of the optical properties is consistent with strong-field-induced electroabsorption. These processes are pertinent to a wide range of nonlinear terahertz-driven light-matter interactions anticipated at accelerator-based sources.

  14. Influence of GaAs surface termination on GaSb/GaAs quantum dot structure and band offsets

    SciTech Connect (OSTI)

    Zech, E. S.; Chang, A. S.; Martin, A. J.; Canniff, J. C.; Millunchick, J. M. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)] [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Lin, Y. H. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)] [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Goldman, R. S. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)

    2013-08-19T23:59:59.000Z

    We have investigated the influence of GaAs surface termination on the nanoscale structure and band offsets of GaSb/GaAs quantum dots (QDs) grown by molecular-beam epitaxy. Transmission electron microscopy reveals both coherent and semi-coherent clusters, as well as misfit dislocations, independent of surface termination. Cross-sectional scanning tunneling microscopy and spectroscopy reveal clustered GaSb QDs with type I band offsets at the GaSb/GaAs interfaces. We discuss the relative influences of strain and QD clustering on the band offsets at GaSb/GaAs interfaces.

  15. The Influence of High-Energy Lithium Ion Irradiation on Electrical Characteristics of Silicon and GaAs Solar Cells

    E-Print Network [OSTI]

    B. Jayashree; Ramani; M. C. Radhakrishna; Anil Agrawal; Saif Ahmad Khan; A. Meulenberg

    2006-10-22T23:59:59.000Z

    Space-grade Si and GaAs solar cells were irradiated with 15 & 40 MeV Li ions. Illuminated (AM0 condition) and unilluminated I-V curves reveal that the effect of high-energy Li ion irradiation has produced similar effects to that of proton irradiation. However, an additional, and different, defect mechanism is suggested to dominate in the heavier-ion results. Comparison is made with proton-irradiated solar-cell work and with non-ionizing energy-loss (NIEL) radiation-damage models.

  16. Novel Metal-Sulfur-Based Air-Stable Passivation of GaAs with Very Low Surface State Densities

    SciTech Connect (OSTI)

    Ashby, Carol I.H.; Baca, Albert G.; Chang, P.-C; Hafich, M.J.; Hammons, B.E.; Zavadil, Kevin R.

    1999-08-09T23:59:59.000Z

    A new air-stable electronic surface passivation for GaAs and other III-V compound semiconductors that employs sulfur and a suitable metal ion, e.g., Zn, and that is robust towards plasma dielectric deposition has been developed. Initial improvements in photoluminescence are twice that of S-only treatments and have been preserved for >11 months with SiO{sub x}N{sub y} dielectric encapsulation. Photoluminescence and X-ray photoelectron spectroscopies indicate that the passivation consists of two major components with one being stable for >2 years in air. This process improves heterojunction bipolar transistor current gain for both large and small area devices.

  17. Nucleation, transition, and maturing of the self-assembled Au droplets on various type-A GaAs substrates

    SciTech Connect (OSTI)

    Li, Ming-Yu, E-mail: mingyuli.oliver@gmail.com; Sui, Mao; Kim, Eun-Soo [College of Electronics and Information, Kwangwoon University, Nowon-gu, Seoul 139-701 (Korea, Republic of); Lee, Jihoon, E-mail: jihoonleenano@gmail.com [College of Electronics and Information, Kwangwoon University, Nowon-gu, Seoul 139-701 (Korea, Republic of); Institute of Nanoscale Science and Engineering, University of Arkansas, Fayetteville, Arkansas 72701 (United States)

    2014-08-28T23:59:59.000Z

    In this study, the fabrication of self-assembled Au droplets is successfully demonstrated on various type-A GaAs substrates: (711)A, (511)A, (411)A, and (311)A. The nucleation of the self-assembled tiny Au clusters is observed at 300?°C. As an intermediate stage, corrugated Au nanostructures are clearly observed at 350?°C on various type-A GaAs surfaces, rarely witnessed on other substrates. Based on the Volmer-Weber growth mode, the dome-shaped Au droplets with excellent uniformities are successfully fabricated between 500 and 550?°C. As a function of annealing temperature, the self-assembled Au droplets show the increased dimensions including average height and diameter, compensated by the decreased average density. Depending on the substrate indices utilized, the size and density of Au droplets show clear differences throughout the whole temperature range. The results are symmetrically analyzed by using atomic force microscope images, cross-sectional line-profiles, size and density plots, height distribution histograms, and Fourier filter transform power spectra.

  18. High-field electroluminescence in semiconductor tunnel junctions with a Mn-doped GaAs layer

    SciTech Connect (OSTI)

    Hai, Pham Nam [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-0033 (Japan); Yatsui, Takashi; Ohtsu, Motoichi; Tanaka, Masaaki [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Nanophotonics Research Center, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2014-09-21T23:59:59.000Z

    We investigated high-field electroluminescence (EL) in semiconductor tunnel junctions with a Mn-doped GaAs layer (here, referred to as GaAs:Mn). Besides the band-gap emission of GaAs, the EL spectra show visible light emissions with two peaks at 1.94?eV and 2.19?eV, which are caused by d-d transitions of the Mn atoms excited by hot electrons. The threshold voltages for band-gap and visible light EL in the tunnel junctions with a GaAs:Mn electrode are 1.3?V higher than those of GaAs:Mn excited by hot holes in reserve biased p{sup +}-n junctions, which is consistent with the hot carrier transport in the band profiles of these structures. Our EL results at room temperature show that the electron temperature in GaAs:Mn can be as high as ?700?K for a low input electrical power density of 0.4?W/cm{sup 2}, while the lattice temperature of the GaAs:Mn layer can be kept at 340?K.

  19. Self-cleaning and surface recovery with arsine pretreatment in ex situ atomic-layer-deposition of Al2O3 on GaAs

    E-Print Network [OSTI]

    /Thomas Swan close-coupled showerhead cold-wall MOCVD system. The buffer epilayers of GaAs were grown on 2 in for these interfaces. In addition, when designing an in situ MOCVD process, the typical TMA/H2O is incompatible

  20. Ab initio cluster calculations of hydrogenated GaAs,,001... surfaces Chemical Engineering Department, University of California, Los Angeles, California 90095-1592

    E-Print Network [OSTI]

    Li, Lian

    Ab initio cluster calculations of hydrogenated GaAs,,001... surfaces Q. Fu Chemical Engineering Engineering Department, University of California, Los Angeles, California 90095-1592 Received 11 November 1999 Hydrogen adsorption on the 2 4 and 4 2 reconstructions of gallium arsenide 001 has been studied by internal

  1. Synthesis of GaNxAs1-x thin films by pulsed laser melting and rapid thermal annealing (PLM-RTA) of N+-implanted GaAs

    E-Print Network [OSTI]

    2003-01-01T23:59:59.000Z

    energy (eV) Fig. 7 N impl. GaAs PLM+950 o C 10s bamd gap, Eand Rapid Thermal Annealing (PLM-RTA) of N + -implanted GaAsof N (x imp ) and processed by PLM at an energy fluence of

  2. ELSEWER Journal of Magnetism and Magnetic Materials 169 (1997) 261-270 Superparamagnetic behavior of Fe,GaAs precipitates in GaAs

    E-Print Network [OSTI]

    Woodall, Jerry M.

    ELSEWER Journal of Magnetism and Magnetic Materials 169 (1997) 261-270 Superparamagnetic behavior; revised 6 December 1996 Abstract We present magnetization measurements on Fe3GaAs clusters distributed-dependent magnetization well above the blocking temperature indicate a particle size distribution in agreement

  3. Relaxed, high-quality InP on GaAs by using InGaAs and InGaP graded buffers to avoid phase separation

    E-Print Network [OSTI]

    Relaxed, high-quality InP on GaAs by using InGaAs and InGaP graded buffers to avoid phaseAs was 70% of that on bulk InP at both temperatures. To achieve this, graded buffers in the InGaAs, InGaP

  4. Growth, microstructure, and luminescent properties of direct-bandgap InAlP on relaxed InGaAs on GaAs substrates

    E-Print Network [OSTI]

    an impact on the luminescence spectrum. While similar to InGaP in many ways, the greater tendency for phase as the InGaP system, but still has desirable properties. In0.48Al0.52P is lattice- matched to GaAs and has

  5. Compositionally-graded InGaAsInGaP alloys and GaAsSb alloys for metamorphic InP on GaAs

    E-Print Network [OSTI]

    Compositionally-graded InGaAs­InGaP alloys and GaAsSb alloys for metamorphic InP on GaAs Li Yang a of tandem graded layers of InGaAs and InGaP with compositional grading of the In concentration. This tandem

  6. Point contact Andreev spectroscopy of epitaxial Co{sub 2}FeSi Heusler alloys on GaAs (001)

    SciTech Connect (OSTI)

    Lehmann, Hauke; Merkt, Ulrich; Meier, Guido [Institut fuer Angewandte Physik und Zentrum fuer Mikrostrukturforschung, Universitaet Hamburg, Jungiusstrasse 11, 20355 Hamburg (Germany); Scholtyssek, Jan M. [Institut fuer Angewandte Physik und Zentrum fuer Mikrostrukturforschung, Universitaet Hamburg, Jungiusstrasse 11, 20355 Hamburg (Germany); Institut fuer Elektrische Messtechnik und Grundlagen der Elektrotechnik, Technische Universitaet Braunschweig, Hans-Sommer-Strasse 66, 38106 Braunschweig (Germany); Herrmann, Claudia; Herfort, Jens [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2011-09-15T23:59:59.000Z

    The predicted half-metallicity of Co{sub 2}FeSi in combination with its high Curie temperature of above 980 K makes this Heusler alloy interesting for spinelectronics. Thin Co{sub 2}FeSi films are grown by molecular-beam epitaxy on GaAs (001) with a close lattice match. We present a study of point-contact measurements on different films, varying in thickness between 18 nm and 48 nm and in substrate temperature during deposition between 100 deg. C and 300 deg. C. Transport spin polarizations at the Fermi level are determined from differential conductance curves obtained by point-contact Andreev-reflection spectroscopy. A maximum transport spin polarization of about 60% is measured for a 18 nm thin Co{sub 2}FeSi film grown at 200 deg. C.

  7. Electron Transport Behavior on Gate Length Scaling in Sub-50 nm GaAs Metal Semiconductor Field Effect Transistors

    SciTech Connect (OSTI)

    Han, Jaeheon [Department of Electronic Engineering, Kangnam University, 111 Gugal-dong, Giheung-gu, Yongin-city, Gyeonggi-do, Korea 446-702 (Korea, Republic of)

    2011-12-23T23:59:59.000Z

    Short channel GaAs Metal Semiconductor Field Effect Transistors (MESFETs) have been fabricated with gate length to 20 nm, in order to examine the characteristics of sub-50 nm MESFET scaling. Here the rise in the measured transconductance is mainly attributed to electron velocity overshoot. For gate lengths below 40 nm, however, the transconductance drops suddenly. The behavior of velocity overshoot and its degradation is investigated and simulated by using a transport model based on the retarded Langevin equation (RLE). This indicates the existence of a minimum acceleration length needed for the carriers to reach the overshoot velocity. The argument shows that the source resistance must be included as an internal element, or appropriate boundary condition, of relative importance in any model where the gate length is comparable to the inelastic mean free path of the carriers.

  8. Magnetic anisotropies in epitaxial Fe{sub 3}O{sub 4}/GaAs(100) patterned structures

    SciTech Connect (OSTI)

    Zhang, W., E-mail: xiaotur@gmail.com; Zhang, D.; Yuan, S. J.; Huang, Z. C.; Zhai, Y. [Department of Physics, Southeast University, Nanjing 211189 (China); Wong, P. K. J. [NanoElectronics Group, MESA Institute for Nanotechnology, University of Twente, P. O. Box 217, 7500 AE Enschede (Netherlands); Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543 (Singapore); Wu, J. [Department of Physics, University of York, York YO10 5DD (United Kingdom); Xu, Y. B. [Spintronics and Nanodevice Laboratory, Department of Electronics, University of York, York, YO10 5DD (United Kingdom)

    2014-10-15T23:59:59.000Z

    Previous studies on epitaxial Fe{sub 3}O{sub 4} rings in the context of spin-transfer torque effect have revealed complicated and undesirable domain structures, attributed to the intrinsic fourfold magnetocrystalline anisotropy in the ferrite. In this Letter, we report a viable solution to this problem, utilizing a 6-nm-thick epitaxial Fe{sub 3}O{sub 4} thin film on GaAs(100), where the fourfold magnetocrystalline anisotropy is negligible. We demonstrate that in the Fe{sub 3}O{sub 4} planar wires patterned from our thin film, such a unique magnetic anisotropy system has been preserved, and relatively simple magnetic domain configurations compared to those previous reports can be obtained.

  9. Molecular Beam Epitaxial Growth of Bi2Te3 and Sb2Te3 Topological Insulators on GaAs (111) Substrates: A Potential Route to Fabricate Topological Insulator p-n Junction

    E-Print Network [OSTI]

    Zhaoquan Zeng; Timothy A. Morgan; Dongsheng Fan; Chen Li; Yusuke Hirono; Xian Hu; Yanfei Zhao; Joon Sue Lee; Zhiming M. Wang; Jian Wang; Shuiqing Yu; Michael E. Hawkridge; Mourad Benamara; Gregory J. Salamo

    2013-03-11T23:59:59.000Z

    High quality Bi2Te3 and Sb2Te3 topological insulators films were epitaxially grown on GaAs (111) substrate using solid source molecular beam epitaxy. Their growth and behavior on both vicinal and non-vicinal GaAs (111) substrates were investigated by reflection high-energy electron diffraction, atomic force microscopy, x-ray diffraction, and high resolution transmission electron microscopy. It is found that non-vicinal GaAs (111) substrate is better than a vicinal substrate to provide high quality Bi2Te3 and Sb2Te3 films. Hall and magnetoresistance measurements indicate that p type Sb2Te3 and n type Bi2Te3 topological insulator films can be directly grown on a GaAs (111) substrate, which may pave a way to fabricate topological insulator p-n junction on the same substrate, compatible with the fabrication process of present semiconductor optoelectronic devices.

  10. Impact of artificial lateral quantum confinement on exciton-spin relaxation in a two-dimensional GaAs electronic system

    SciTech Connect (OSTI)

    Kiba, Takayuki, E-mail: tkiba@ist.hokudai.ac.jp; Murayama, Akihiro [Graduate School of Information Science and Technology, Hokkaido University, Kita 14, Nishi 9, Kita-ku, Sapporo (Japan); CREST Japan Science and Technology Agency, 5 Sanbancho, Chiyoda-ku, Tokyo (Japan); Tanaka, Toru [Graduate School of Information Science and Technology, Hokkaido University, Kita 14, Nishi 9, Kita-ku, Sapporo (Japan); Tamura, Yosuke [Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai (Japan); Higo, Akio [WPI-AIMR, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai (Japan); Thomas, Cedric [Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai (Japan); CREST Japan Science and Technology Agency, 5 Sanbancho, Chiyoda-ku, Tokyo (Japan); Samukawa, Seiji [Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai (Japan); WPI-AIMR, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai (Japan); CREST Japan Science and Technology Agency, 5 Sanbancho, Chiyoda-ku, Tokyo (Japan)

    2014-10-15T23:59:59.000Z

    We demonstrate the effect of artificial lateral quantum confinement on exciton-spin relaxation in a GaAs electronic system. GaAs nanodisks (NDs) were fabricated from a quantum well (QW) by top-down nanotechnology using neutral-beam etching aided by protein-engineered bio-nano-templates. The exciton-spin relaxation time was 1.4 ns due to ND formation, significantly extended compared to 0.44 ns for the original QW, which is attributed to weakening of the hole-state mixing in addition to freezing of the carrier momentum. The temperature dependence of the spin-relaxation time depends on the ND thickness, reflecting the degree of quantum confinement.

  11. Comparison of luminescent efficiency of InGaAs quantum well structures grown on Si, GaAs, Ge, and SiGe virtual substrate

    E-Print Network [OSTI]

    , and SiGe virtual substrate V. K. Yang, S. M. Ting, M. E. Groenert, M. T. Bulsara, M. T. Currie, C. W efficiency of InGaAs quantum wells on Si via SiGe interlayers, identical In0.2Ga0.8As quantum well structures metalorganic vapor deposition system. The substrates used include GaAs, Si, Ge, and SiGe virtual substrates

  12. Room-temperature cw operation of InGaAsP/InGaP lasers at 727 nm grown on GaAs substrates by liquid phase epitaxy

    SciTech Connect (OSTI)

    Wakao, K.; Nishi, H.; Kusunoki, T.; Isozumi, S.; Ohsaka, S.

    1984-06-01T23:59:59.000Z

    InGaAsP/InGaP lasers emitting at 724--727 nm have been fabricated on GaAs substrates using liquid phase epitaxy. The threshold current is reduced to 8 kA/cm/sup 2/ by thinning the active layer. Room-temperature cw operation is achieved for the first time in the lasing wavelength range below 760 nm in this quaternary system.

  13. Passivation of carbon acceptors during growth of carbon-doped GaAs, InGaAs, and HBTs by MOCVD

    SciTech Connect (OSTI)

    Stockman, S.A.; Hanson, A.W.; Lichtenthal, S.M.; Fresina, M.T.; Hoefler, G.E.; Hsieh, K.C.; Stillman, G.E. (Univ. of Illinois, Urbana (United States))

    1992-12-01T23:59:59.000Z

    Carbon doped p-type GaAs and In[sub 0.53]Ga[sub 0.47]As epitaxial layers were grown by low-pressure metalorganic chemical vapor deposition using CCl[sub 4] as the carbon source. Low-temperature post-growth annealing resulted in a significant increase in the hole concentration for both GaAs and In[sub 0.53]Ga[sub 0.47]As, especially at high doping levels. The most heavily doped GaAs sample had a hole concentration of 3.6 [times] 10[sup 20] cm[sup [minus]3] after a 5 minute anneal at approximately 400[degree]C in N[sub 2], while the hole concentration in In[sub 0.53]Ga[sub 0.47]As reached 1.6 [times] 10[sup 19] cm[sup [minus]3] after annealing. This behavior is attributed to hydrogen passivation of carbon acceptors. Post-growth cool-down in an AsH[sub 3]/H[sub 2] ambient was found to be the most important factor affecting the degree of passivation for single, uncapped GaAs layers. No evidence of passivation is observed in the base region of InGaP/GaAs HBTs grown at approximately 625[degree]C. The effect of n-type cap layers and cool-down sequence on passivation of C-doped InGaAs grown at approximately 525[degree] shows that hydrogen can come from AsH[sub 3], PH[sub 3], or H[sub 2], and can be incorporated during growth and post-growth cool-down. In the case of InP/InGaAs HBTs, significant passivation was found to occur in the C-doped base region. 28 refs., 5 figs., 2 tabs.

  14. Metal-insulator-semiconductor structure on low-temperature grown GaAs M. Young, W. Li, and T. P. Ma

    E-Print Network [OSTI]

    Woodall, Jerry M.

    technique has been used to deposit high-quality insula- tors on Si,16 GaN,17 and GaP.18 It utilizes a high-speed jet of light carrier gases to transport depositing species onto the substrate to form insulator films-type substrate was chosen for potential n-channel de- vices. A 400 nm thick regular p-type GaAs epilayer doped

  15. A 77 GHz Transceiver for Automotive Radar System Using a120nm In AlAs/In GaAs Metamorphic HEMTs

    E-Print Network [OSTI]

    Kwon, Youngwoo

    A 77 GHz Transceiver for Automotive Radar System Using a120nm 0.4 0.35 In AlAs/In GaAs Metamorphic-mail:ykwon@snu.ac.kr) Abstract -- In this work, we demonstrate a compact 77GHz single-chip transceiver for an automotive radar at the transmitter and a 5dB conversion gain at the receiver. Index Terms -- Automotive radar, 77GHz, MHEMT, MMIC

  16. Discrimination between energy transfer and back transfer processes for GaAs host and Er luminescent dopants using electric response analysis

    SciTech Connect (OSTI)

    Ishii, Masashi, E-mail: ISHII.Masashi@nims.go.jp [National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0047 (Japan); Koizumi, Atsushi; Fujiwara, Yasufumi [Division of Materials and Manufacturing Science, Graduate School of Engineering Osaka University, Suita, Osaka 565-0871 (Japan); Takeda, Yoshikazu [Nagoya Industrial Science Research Institute, Nagoya, Aichi 464-0819 (Japan)

    2014-04-07T23:59:59.000Z

    The energy transfer and back transfer processes of GaAs co-doped with Er and O (GaAs:Er,O) were experimentally distinguished by using a frequency response analysis of the AC photocurrent. The results were achieved by using the difference in the frequency dispersion between (1) the dispersion of the energy transfer, which is triggered by the trapping of free charges in the GaAs host and is represented with the Debye relaxation response and (2) the dispersion of the energy back transfer, which is induced by non-radiative transition of 4f bound electrons in the Er dopants and is described with a Lorentzian. The Debye relaxation response found in GaAs:Er,O provided a charge trapping time that was dependent on temperature, which was well correlated with the thermal quenching property of intense intra-4f-shell luminescence. The spectral shape of the Lorentzian dependence on the temperature was explained with the thermal excitation of Er 4f electrons and release of trapped charges in GaAs. The thermal excitation and release of charges consistently explained the characteristics of weak 4f luminescence in low- and high-temperature regions, respectively.

  17. Low-temperature synthesis of gallium nitride thin films using electron cyclotron resonance plasma assisted pulsed laser deposition from a GaAs target

    SciTech Connect (OSTI)

    Sun, J.; Wu, A.M.; Xu, N.; Ying, Z.F.; Shen, X.K.; Dong, Z.B.; Wu, J.D.; Shi, L.Q. [State Key Laboratory for Advanced Photonic Materials and Devices, Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China); Institute of Modern Physics, Fudan University, Shanghai 200433 (China)

    2005-11-15T23:59:59.000Z

    Using reactive pulsed laser deposition assisted by electron cyclotron resonance (ECR) plasma, we have synthesized GaN thin films from a polycrystalline GaAs target at low temperatures. This was achieved by ablating the GaAs target in the reactive environment of a nitrogen plasma generated from ECR microwave discharge in pure nitrogen gas and depositing the films with concurrent bombardment by the low-energy nitrogen plasma stream. High-energy ion backscattering spectroscopy analysis shows that the synthesized films are gallium rich. Characterizations by x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy confirm the presence of GaN bonds in the films. The recorded absorption spectrum also reveals GaN stretching mode characteristic of the hexagonal GaN phase. The synthesized GaN films are transparent in the visible region and have a band gap of 3.38 eV. Optical emission from the plume during film deposition reveals that the plume created by pulsed laser ablation of the GaAs target consists mainly of monoatomic atoms and ions of gallium and arsenic. Mechanisms responsible for the formation of GaN molecules and the growth of GaN films are also discussed.

  18. Gypsum, Colorado: Energy Resources | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page onYou are now leaving Energy.gov You are now leaving Energy.gov You are8COaBulkTransmissionSitingProcess.pdfGetec AG| Open EnergyGuntersville Electric BoardGwinnett County,Gyatri

  19. Charge and fluence lifetime measurements of a dc high voltage GaAs photogun at high average current

    SciTech Connect (OSTI)

    J. Grames, R. Suleiman, P.A. Adderley, J. Clark, J. Hansknecht, D. Machie, M. Poelker, M.L. Stutzman

    2011-04-01T23:59:59.000Z

    GaAs-based dc high voltage photoguns used at accelerators with extensive user programs must exhibit long photocathode operating lifetime. Achieving this goal represents a significant challenge for proposed high average current facilities that must operate at tens of milliamperes or more. This paper describes techniques to maintain good vacuum while delivering beam, and techniques that minimize the ill effects of ion bombardment, the dominant mechanism that reduces photocathode yield of a GaAs-based dc high voltage photogun. Experimental results presented here demonstrate enhanced lifetime at high beam currents by: (a) operating with the drive laser beam positioned away from the electrostatic center of the photocathode, (b) limiting the photocathode active area to eliminate photoemission from regions of the photocathode that do not support efficient beam delivery, (c) using a large drive laser beam to distribute ion damage over a larger area, and (d) by applying a relatively low bias voltage to the anode to repel ions created within the downstream beam line. A combination of these techniques provided the best total charge extracted lifetimes in excess of 1000 C at dc beam currents up to 9.5 mA, using green light illumination of bulk GaAs inside a 100 kV photogun.

  20. Spectroscopic ellipsometry studies of GaN films deposited by reactive rf sputtering of GaAs target

    SciTech Connect (OSTI)

    Biswas, A.; Bhattacharyya, D.; Sahoo, N. K. [Spectroscopy Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Yadav, Brajesh S.; Major, S. S. [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400 076 (India); Srinivasa, R. S. [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400 076 (India)

    2008-04-15T23:59:59.000Z

    GaN films have been deposited by reactive rf sputtering of GaAs target in 100% nitrogen ambient on quartz substrates at different substrate temperatures ranging from room temperature to 700 deg. C. A series of films, from arsenic-rich amorphous to nearly arsenic-free polycrystalline hexagonal GaN, has been obtained. The films have been characterized by phase modulated spectroscopic ellipsometry to obtain the optical parameters, viz., fundamental band gap, refractive index, and extinction coefficient, and to understand their dependence on composition and microstructure. A generalized optical dispersion model has been used to carry out the ellipsometric analysis for amorphous and polycrystalline GaN films and the variation of the optical parameters of the films has been studied as a function of substrate temperature. The refractive index values of polycrystalline films with preferred orientation of crystallites are slightly higher (2.2) compared to those for amorphous and randomly oriented films. The dominantly amorphous GaN film shows a band gap of 3.47 eV, which decreases to 3.37 eV for the strongly c-axis oriented polycrystalline film due to the reduction in amorphous phase content with increase in substrate temperature.

  1. The influence of a doping profile on the characteristics of an ion-implanted GaAs field-effect transistor with a Schottky barrier

    SciTech Connect (OSTI)

    Shestakov, A. K., E-mail: shestakov@thermo.isp.nsc.ru; Zhuravlev, K. S. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

    2011-12-15T23:59:59.000Z

    A GaAs field-effect ion-implanted transistor with a Schottky barrier is simulated. The doping profile obtained when doping through an insulator mask is determined and the dependences of the static transistor characteristics on the parameters of the doping profile are calculated and analyzed. The physical processes controlling the transistor characteristics in the case of a variation in the parameters of its doping profile and the coefficient of compensation of the substrate are studied. Based on calculations, the optimal doping-profile parameters ensuring the best characteristics for transistors are predicted.

  2. Optical and digital GaAs technologies for signal-processing applications; Proceedings of the Meeting, Orlando, FL, Apr. 16-18, 1990

    SciTech Connect (OSTI)

    Bendett, M.P.; Butler, D.H., Jr.; Prabhakar, A.; Yang, A.; (Honeywell, Inc., Minneapolis, MN; Booz, Allen and Hamilton, Inc., Bethesda, MD; DARPA, Arlington, VA)

    1990-01-01T23:59:59.000Z

    Practical problems that need to be solved for the introduction of optical modules into processing systems are reviewed. Some papers deal with the state of the art in such key devices as Bragg cells, spatial light modulators, and fast CCDs. Issues unique to optical packaging are also highlightened. New architectures to enable real-time operations are demonstrated, and optical interconnects for parallel processors are discussed. Particular attention is given to the status and operational advantages of government-sponsored efforts to upgrade existing military systems with digital GaAs signal processors and the state of the art in computer-aided design and advanced system architectures.

  3. Evaluation of thickness and strain of thin planar layers of InAs on GaAs(001) using spectroscopic ellipsometry

    SciTech Connect (OSTI)

    Eyink, K. G.; Szmulowicz, F.; Esposito, D.; Grazulis, L.; Hill, M.; Mahalingam, K.; Aronow, A. J. [Nano Electronic Materials Branch (RXAN), Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433-7707 (United States)

    2014-07-21T23:59:59.000Z

    We develop a technique for accurately measuring thickness of planar InAs films grown on (001) GaAs by spectroscopic ellipsometry, using bulk optical constants. We observe that the critical point structure for the E{sub 1} and E{sub 1}?+??{sub 1} transitions extracted from the measured dielectric properties varies with strain in the layer. Transmission electron microscopy confirms the extracted thickness and measures the residual strain based on the dislocation spacing in the film. At small thickness, the E{sub 1} critical point is seen to markedly deviate from the dependence predicted by deformation potential theory and appears to be consistent with additional quantum confinement effects.

  4. InGaAsN Solar Cells with 1.0eV Bandgap, Lattice Matched to GaAs

    SciTech Connect (OSTI)

    Allerman, A.A.; Banas, J.J.; Gee, J.M.; Hammons, B.E.; Jones, E.D.; Kurtz, S.R.

    1998-11-24T23:59:59.000Z

    The design, growth by metal-organic chemical vapor deposition, and processing of an In{sub 0.07}Ga{sub 0.93}As{sub 0.98}N{sub 0.02} solar Al, with 1.0 ev bandgap, lattice matched to GaAs is described. The hole diffusion length in annealed, n-type InGaAsN is 0.6-0.8 pm, and solar cell internal quantum efficiencies > 70% arc obwined. Optical studies indicate that defects or impurities, from InGAsN doping and nitrogen incorporation, limit solar cell performance.

  5. Localization-delocalization transition of electrons at the percolation threshold of semiconductor GaAs1–xNx alloys: The appearance of a mobility edge

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Alberi, K.; Fluegel, B.; Beaton, D. A.; Ptak, A. J.; Mascarenhas, A.

    2012-07-01T23:59:59.000Z

    Electrons in semiconductor alloys have generally been described in terms of Bloch states that evolve from constructive interference of electron waves scattering from perfectly periodic potentials, despite the loss of structural periodicity that occurs on alloying. Using the semiconductor alloy GaAs??xNx as a prototype, we demonstrate a localized to delocalized transition of the electronic states at a percolation threshold, the emergence of a mobility edge, and the onset of an abrupt perturbation to the host GaAs electronic structure, shedding light on the evolution of electronic structure in these abnormal alloys.

  6. Final Technical Progress Report: High-Efficiency Low-Cost Thin-Film GaAs Photovoltaic Module Development Program; July 14, 2010 - January 13, 2012

    SciTech Connect (OSTI)

    Mattos, L.

    2012-03-01T23:59:59.000Z

    This is the final technical progress report of the High-Efficiency Low-Cost Thin-Film GaAs Photovoltaic Module Development Program. Alta Devices has successfully completed all milestones and deliverables established as part of the NREL PV incubator program. During the 18 months of this program, Alta has proven all key processes required to commercialize its solar module product. The incubator focus was on back end process steps directed at conversion of Alta's high quality solar film into high efficiency 1-sun PV modules. This report describes all program deliverables and the work behind each accomplishment.

  7. Effects of atomic hydrogen and deuterium exposure on high polarization GaAs photocathodes M. Baylac,* P. Adderley, J. Brittian, J. Clark, T. Day, J. Grames, J. Hansknecht, M. Poelker, M. Stutzman, and A. T. Wu

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    chambers. The photocathode is formed when cesium (Cs) and nitrogen trifluoride (NF3) gas are applied cleaning remains an effective technique to remove surface contamination from bulk GaAs. A note- worthy. This statement stems from the realization, made over the course of years, that contamination is introduced onto

  8. NMR relaxometry study of plaster mortar with polymer additives

    SciTech Connect (OSTI)

    Jumate, E.; Manea, D. [Technical University of Cluj-Napoca, Faculty of Civil Engineering. 15 C Daicoviciu Str., 400020, Cluj-Napoca (Romania)] [Technical University of Cluj-Napoca, Faculty of Civil Engineering. 15 C Daicoviciu Str., 400020, Cluj-Napoca (Romania); Moldovan, D.; Fechete, R. [Technical University of Cluj-Napoca, Department of Physics and Chemistry, 25 G. Baritiu Str., 400027, Cluj-Napoca (Romania)] [Technical University of Cluj-Napoca, Department of Physics and Chemistry, 25 G. Baritiu Str., 400027, Cluj-Napoca (Romania)

    2013-11-13T23:59:59.000Z

    The cement mixed with water forms a plastic paste or slurry which stiffness in time and finally hardens into a resistant stone. The addition of sand aggregates, polymers (Walocel) and/or calcium carbonate will modify dramatically the final mortar mechanic and thermal properties. The hydration processes can be observed using the 1D NMR measurements of transverse T{sub 2} relaxation times distributions analysed by a Laplace inversion algorithm. These distributions were obtained for mortar pasta measured at 2 hours after preparation then at 3, 7 and 28 days after preparation. Multiple components are identified in the T{sub 2} distributions. These can be associated with the proton bounded chemical or physical to the mortar minerals characterized by a short T{sub 2} relaxation time and to water protons in pores with three different pore sizes as observed from SEM images. The evaporation process is faster in the first hours after preparation, while the mortar hydration (bonding of water molecules to mortar minerals) can be still observed after days or months from preparation. Finally, the mechanic resistance was correlated with the transverse T{sub 2} relaxation rates corresponding to the bound water.

  9. Seismic load-resisting capacity of plastered straw bale walls

    E-Print Network [OSTI]

    Hsiaw, Jennifer S. (Jennifer Sing-Yee)

    2010-01-01T23:59:59.000Z

    Straw bales have been incorporated into buildings for centuries, but only recently have they been explored in academic settings for their structural potential. Straw bale building is encountering a growing audience due to ...

  10. Effect of Inert Gas Additive Species on Cl(2) High Density Plasma Etching of Compound Semiconductors: Part 1. GaAs and GaSb

    SciTech Connect (OSTI)

    Abernathy, C.R.; Cho, H.; Hahn, Y.B.; Hays, D.C.; Jung, K.B.; Pearton, S.J.; Shul, R.J.

    1998-12-23T23:59:59.000Z

    The role of the inert gas additive (He, Ar, Xe) to C12 Inductively Coupled Plasmas for dry etching of GaAs and GaSb was examined through the effect on etch rate, surface roughness and near-surface stoichiometry. The etch rates for both materials go through a maximum with Clz 0/0 in each type of discharge (C12/'He, C12/Ar, C12/Xc), reflecting the need to have efficient ion-assisted resorption of the etch products. Etch yields initially increase strongly with source power as the chlorine neutral density increases, but decrease again at high powers as the etching becomes reactant-limited. The etched surfaces are generally smoother with Ax or Xe addition, and maintain their stoichiometry.

  11. Repetition of the shape of the ultrafast self-modulation of the optical absorption spectrum upon varying the energy of pulse of GaAs pumping

    SciTech Connect (OSTI)

    Ageeva, N. N.; Bronevoi, I. L., E-mail: bil@cplire.ru; Zabegaev, D. N.; Krivonosov, A. N. [Russian Academy of Sciences, Kotel'nikov Institute of Radio Engineering and Electronics (Russian Federation)

    2010-10-15T23:59:59.000Z

    Ultrafast self-modulation of the fundamental optical absorption emerges during intense picosecond optical pumping of GaAs and, according to the main assumption, reflects self-oscillations of depletion of electron populations in the conduction band. In this study, the quantitatively confirmed explanation of previously experimentally found cyclic repetition of the form of ultrafast self-modulation of the absorption spectrum upon varying the energy of the pumping pulse and fixed delay between pumping and probing (the measurement of absorption) is given. Repetition of the shape is explained by varying the phase of self-oscillations of the optical absorption. The explanation is based on the previously found experimentally dependence of the frequency of self-oscillations of absorption on the pumping energy. Therefore, this is also a new confirmation of the mentioned dependence (which satisfactorily coincides with a similar calculated dependence of the frequency of self-oscillations of depletion of populations).

  12. Polarity driven simultaneous growth of free-standing and lateral GaAsP epitaxial nanowires on GaAs (001) substrate

    SciTech Connect (OSTI)

    Sun, Wen; Xu, Hongyi [Materials Engineering, The University of Queensland, St Lucia QLD 40732 (Australia)] [Materials Engineering, The University of Queensland, St Lucia QLD 40732 (Australia); Guo, Yanan [Materials Engineering, The University of Queensland, St Lucia QLD 40732 (Australia) [Materials Engineering, The University of Queensland, St Lucia QLD 40732 (Australia); Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra ACT 0200 (Australia); Gao, Qiang; Hoe Tan, Hark; Jagadish, Chennupati [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra ACT 0200 (Australia)] [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra ACT 0200 (Australia); Zou, Jin, E-mail: j.zou@uq.edu.au [Materials Engineering, The University of Queensland, St Lucia QLD 40732 (Australia) [Materials Engineering, The University of Queensland, St Lucia QLD 40732 (Australia); Centre for Microscopy and Microanalysis, The University of Queensland, St Lucia QLD 4072 (Australia)

    2013-11-25T23:59:59.000Z

    Simultaneous growth of ?111?{sub B} free-standing and ±[110] lateral GaAsP epitaxial nanowires on GaAs (001) substrates were observed and investigated by electron microscopy and crystallographic analysis. It was found that the growth of both free-standing and lateral ternary nanowires via Au catalysts was driven by the fact that Au catalysts prefer to maintain low-energy (111){sub B} interfaces with surrounding GaAs(P) materials: in the case of free-standing nanowires, Au catalysts maintain (111){sub B} interfaces with their underlying GaAsP nanowires; while in the case of lateral nanowires, each Au catalyst remain their side (111){sub B} interfaces with the surrounding GaAs(P) material during the lateral nanowire growth.

  13. Pre-photolithographic GaAs surface treatment for improved photoresist adhesion during wet chemical etching and improved wet etch profiles.

    SciTech Connect (OSTI)

    Martinez, Marino John; Clevenger, Jascinda; Austin, Franklin H., IV (, LMATA, Albuquerque, NM); Sullivan, Charles Thomas; Patrizi, Gary A.; Romero, Katherine (LMATA, Albuquerque, NM); Timon, Robert P.; Vigil, Pablita S. (LMATA, Albuquerque, NM); Grine, Alejandro J.

    2010-05-01T23:59:59.000Z

    Results of several experiments aimed at remedying photoresist adhesion failure during spray wet chemical etching of InGaP/GaAs NPN HBTs are reported. Several factors were identified that could influence adhesion and a Design of Experiment (DOE) approach was used to study the effects and interactions of selected factors. The most significant adhesion improvement identified is the incorporation of a native oxide etch immediately prior to the photoresist coat. In addition to improving adhesion, this pre-coat treatment also alters the wet etch profile of (100) GaAs so that the reaction limited etch is more isotropic compared to wafers without surface treatment; the profiles have a positive taper in both the [011] and [011] directions, but the taper angles are not identical. The altered profiles have allowed us to predictably yield fully probe-able HBTs with 5 x 5 {micro}m emitters using 5200 {angstrom} evaporated metal without planarization.

  14. Co doping enhanced giant magnetocaloric effect in Mn{sub 1-x}Co{sub x}As films epitaxied on GaAs (001)

    SciTech Connect (OSTI)

    Xu, P. F.; Nie, S. H.; Meng, K. K.; Wang, S. L.; Chen, L.; Zhao, J. H. [State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China)

    2010-07-26T23:59:59.000Z

    A giant magnetocaloric effect was found in series of Mn{sub 1-x}Co{sub x}As films epitaxied on GaAs (001). The maximum magnetic entropy change caused by a magnetic field of 4 T is as large as 25 J/kg K around room temperature, which is about twice the value of pure MnAs film. The observed small thermal hysteresis is more suitable for practical application. Growing of layered Mn{sub 1-x}Co{sub x}As films with Co concentration changing gradually may draw layered active magnetic regenerator refrigerators closer to practical application. Our experimental result may provide the possibility for the combination of magnetocaloric effect and microelectronic circuitry.

  15. Structural properties of Bi{sub 2}Te{sub 3} and Bi{sub 2}Se{sub 3} topological insulators grown by molecular beam epitaxy on GaAs(001) substrates

    SciTech Connect (OSTI)

    Liu, X.; Leiner, J.; Dobrowolska, M.; Furdyna, J. K. [Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Smith, D. J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States); Fan, J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States); Center for Photonics Innovation, Arizona State University, Tempe, Arizona 85287 (United States); Zhang, Y.-H. [Center for Photonics Innovation, Arizona State University, Tempe, Arizona 85287 (United States); School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85287 (United States); Cao, H.; Chen, Y. P. [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Kirby, B. J. [Center for Neutron Research, NIST, Gaithersburg, Maryland 20899 (United States)

    2011-10-24T23:59:59.000Z

    Thin films of Bi{sub 2}Te{sub 3} and Bi{sub 2}Se{sub 3} have been grown on deoxidized GaAs(001) substrates using molecular beam epitaxy. Cross-sectional transmission electron microscopy established the highly parallel nature of the Te(Se)-Bi-Te(Se)-Bi-Te(Se) quintuple layers deposited on the slightly wavy GaAs substrate surface and the different crystal symmetries of the two materials. Raman mapping confirmed the presence of the strong characteristic peaks reported previously for these materials in bulk form. The overall quality of these films reveals the potential of combining topological insulators with ferromagnetic semiconductors for future applications.

  16. MS Exam, Fall 2012, Solid State Electronic Devices (ECE 230A-B) 1. III-V compound semiconductor GaAs has two families of cleavage planes (110) and

    E-Print Network [OSTI]

    Wang, Deli

    MS Exam, Fall 2012, Solid State Electronic Devices (ECE 230A-B) ECE230A: 1. III-V compound of GaAs crystal. 1 #12;MS Exam, Fall 2012, Solid State Electronic Devices (ECE 230A-B) ECE 230B: Assume silicon, room temperature, complete ionization. 1. For an abrupt n+-p diode in Si, the n+ doping is 1020

  17. Wafer Bonding and Epitaxial Transfer of GaSb-based Epitaxy to GaAs for Monolithic Interconnection of Thermophotovoltaic Devices

    SciTech Connect (OSTI)

    C.A. Wang; D.A. Shiau; P.G. Murphy; P.W. O'brien; R.K. Huang; M.K. Connors; A.C. Anderson; D. Donetsky; S. Anikeev; G. Belenky; D.M. Depoy; G. Nichols

    2003-06-16T23:59:59.000Z

    GaInAsSb/AlGaAsSb/InAsSb/GaSb epitaxial layers were bonded to semi-insulating GaAs handle wafers with SiO{sub x}/Ti/Au as the adhesion layer for monolithic interconnection of thermophotovoltaic (TPV) devices. Epitaxial transfer was completed by removal of the GaSb substrate, GaSb buffer, and InAsSb etch-stop layer by selective chemical etching. The SiO{sub x}/TiAu provides not only electrical isolation, but also high reflectivity and is used as an internal back-surface reflector. Characterization of wafer-bonded epitaxy by high-resolution x-ray diffraction and time-decay photoluminescence indicates minimal residual stress and enhancement in optical quality. 0.54-eV GaInAsSb cells were fabricated and monolithically interconnected in series. A 10-junction device exhibited linear voltage building with an open-circuit voltage of 1.8 V.

  18. Conversion of above- and below-bandgap photons via InAs quantum dot media embedded into GaAs solar cell

    SciTech Connect (OSTI)

    Sablon, K.; Little, J. [U.S. Army Research Laboratory, Adelphi, Maryland 20783 (United States); Vagidov, N. [Optoelectronic Nanodevices LLC, Amherst, New York 14226 (United States); Li, Y.; Mitin, V.; Sergeev, A. [EE Department, University at Buffalo—SUNY, Buffalo, New York 14260 (United States)

    2014-06-23T23:59:59.000Z

    Quantum dots (QDs) provide photovoltaic conversion of below-bandgap photons due to multistep electron transitions. QDs also increase conversion efficiency of the above-bandgap photons due to extraction of electrons from QDs via Coulomb interaction with hot electrons excited by high-energy photons. Nanoscale potential profile (potential barriers) and nanoscale band engineering (AlGaAs atomically thin barriers) allow for suppression of photoelectron capture to QDs. To study these kinetic effects and to distinguish them from the absorption enhancement due to light scattering on QDs, we investigate long, 3-?m base GaAs devices with various InAs QD media with 20 and 40 QD layers. Quantum efficiency measurements show that, at least at low doping, the multistep processes in QD media are strongly affected by the wetting layer (WL). The QD media with WLs provide substantial conversion of below-bandgap photons and for devices with 40 QD layers the short circuit current reaches 29.2?mA/cm{sup 2}. The QD media with band-engineered AlGaAs barriers and reduced wetting layers (RWL) enhance conversion of high-energy photons and decrease the relaxation (thermal) losses.

  19. Imaging with Mass Spectrometry: A SIMS and VUV-Photoionization Study of Ion-Sputtered Atoms and Clusters from GaAs and Au

    SciTech Connect (OSTI)

    Takahashi, Lynelle; Zhou, Jia; Wilson, Kevin R.; Leone, Stephen R.; Ahmed, Musahid

    2008-12-05T23:59:59.000Z

    A new mass spectrometry surface imaging method is presented in which ion-sputtered neutrals are postionized by wavelength-tunable vacuum ultraviolet (VUV) light from a synchrotron source. Mass spectra and signal counts of the photoionized neutrals from GaAs (100) and Au are compared to those of the secondary ions. While clusters larger than dimers are more efficiently detected as secondary ions, certain species, such as As2, Au and Au2, are more efficiently detected through the neutral channel. Continuously tuning the photon wavelength allows photoionization efficiency (PIE) curves to be obtained for sputtered Asm (m=1,2) and Aun (n=1-4). From the observed ionization thresholds, sputtered neutral As and Au show no clear evidence of electronic excitation, while neutral clusters have photoionization onsets shifted to lower energies by ~;;0.3 eV. These shifts are attributed to unresolved vibrational and rotational excitations. High-spatial resolution chemical imaging with synchrotron VUV postionization is demonstrated at two different photon energies using a copper TEM grid embedded in indium. The resulting images are used to illustrate the use of tunable VUV light for verifying mass peak assignments by exploiting the unique wavelength-dependent PIE of each sputtered neutral species. This capability is valuable for identifying compounds when imaging chemically complex systems with mass spectrometry-based techniques.

  20. Spin decoherence in n-type GaAs: The effectiveness of the third-body rejection method for electron-electron scattering

    SciTech Connect (OSTI)

    Marchetti, Gionni, E-mail: gionnimarchetti@gmail.com; Hodgson, Matthew, E-mail: matthew.hodgson@york.ac.uk; D'Amico, Irene, E-mail: irene.damico@york.ac.uk [Department of Physics, University of York, York, Heslington YO10 5DD (United Kingdom)

    2014-10-28T23:59:59.000Z

    We study the spin decoherence in n-type bulk GaAs for moderate electronic densities at room temperature using the Ensemble Monte Carlo method. We demonstrate that a technique called “third-body rejection method” devised by B. K. Ridley, J. Phys. C: Solid State Phys. 10, 1589 (1977) can be successfully adapted to Ensemble Monte Carlo method and used to tackle the problem of the electron-electron contribution to spin decoherence in the parameter region under study, where the electron-electron interaction can be reasonably described by a Yukawa potential. This scattering technique is employed in a doping region where one can expect that multiple collisions may play a role in carrier dynamics. By this technique, we are able to calculate spin relaxation times which are in very good agreement with the experimental results found by Oertel et al., Appl. Phys. Lett. 93, 13 (2008). Through this method, we show that the electron-electron scattering is overestimated in Born approximation, in agreement with previous results obtained by C. A. Kukkonen and H. Smith, Phys. Rev. B 8, 4601 (1973).

  1. Catastrophic degradation of InGaAsP/InGaP double-heterostructure lasers grown on (001) GaAs substrates by liquid-phase epitaxy

    SciTech Connect (OSTI)

    Ueda, O.; Wakao, K.; Komiya, S.; Yamaguchi, A.; Isozumi, S.; Umebu, I.

    1985-12-01T23:59:59.000Z

    Catastrophically degraded InGaAsP/InGaP double-heterostructure lasers grown on (001) GaAs substrates by liquid-phase epitaxy, emitting at 727 and 810 nm are investigated by photoluminescence topography, scanning electron microscopy, transmission electron microscopy, and energy dispersive x-ray spectroscopy. The degradation is mainly due to catastrophic optical damage at the facet, i.e., development of <110> dark-line defects from the facet, and rarely due to catastrophic optical damage at some defects, i.e., development of <110> dark-line defects from the defects inside the stripe region. These <110> dark-line defects correspond to complicated dislocation networks connected with dark knots, and are quite similar to those observed in catastrophically degraded GaAlAs/GaAs double-heterostructure lasers. The degradation characteristics of the InGaAsP/InGaP double-heterostructure lasers are rather similar to those in GaAlAs/GaAs double-heterostructure lasers concerning the catastrophic degradation.

  2. Sputtering of Si, SiC, InAs, InP, Ge, GaAs, GaSb, and GaN by electrosprayed nanodroplets

    SciTech Connect (OSTI)

    Borrajo-Pelaez, Rafael; Grustan-Gutierrez, Enric; Gamero-Castaño, Manuel, E-mail: mgameroc@uci.edu [Department of Mechanical and Aerospace Engineering, University of California, Irvine, California 92697 (United States)

    2013-11-14T23:59:59.000Z

    This article presents a characterization of the damage caused by energetic beams of electrosprayed nanodroplets striking the surfaces of single-crystal semiconductors including Si, SiC, InAs, InP, Ge, GaAs, GaSb, and GaN. The sputtering yield (number of atoms ejected per projectile's molecule), sputtering rate, and surface roughness are measured as functions of the beam acceleration potential. The maximum values of the sputtering yields range between 1.9 and 2.2 for the technological important but difficult to etch SiC and GaN respectively, and 4.5 for Ge. The maximum sputtering rates for the non-optimized beam flux conditions used in our experiments vary between 409?nm/min for SiC and 2381?nm/min for GaSb. The maximum sputtering rate for GaN is 630?nm/min. Surface roughness increases modestly with acceleration voltage, staying within 2?nm and 20?nm for all beamlet acceleration potentials and materials except Si. At intermediate acceleration potentials, the surface of Si is formed by craters orders of magnitude larger than the projectiles, yielding surface roughness in excess of 60?nm. The effect of projectile dose is studied in the case of Si. This parameter is correlated with the formation of the large craters typical of Si, which suggests that the accumulation of damage following consecutive impacts plays an important role in the interaction between beamlet and target.

  3. Structural and band alignment properties of Al{sub 2}O{sub 3} on epitaxial Ge grown on (100), (110), and (111)A GaAs substrates by molecular beam epitaxy

    SciTech Connect (OSTI)

    Hudait, M. K.; Zhu, Y. [Advanced Devices and Sustainable Energy Laboratory (ADSEL), Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Maurya, D.; Priya, S. [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Patra, P. K. [Department of Biomedical Engineering and Department of Mechanical Engineering, University of Bridgeport, Bridgeport, Connecticut 06604 (United States); Ma, A. W. K. [Department of Chemical and Biomolecular Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Aphale, A.; Macwan, I. [Department of Electrical and Computer Engineering, University of Bridgeport, Bridgeport, Connecticut 06604 (United States)

    2013-04-07T23:59:59.000Z

    Structural and band alignment properties of atomic layer Al{sub 2}O{sub 3} oxide film deposited on crystallographically oriented epitaxial Ge grown in-situ on (100), (110), and (111)A GaAs substrates using two separate molecular beam epitaxy chambers were investigated using cross-sectional transmission microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). High-resolution triple axis x-ray measurement demonstrated pseudomorphic and high-quality Ge epitaxial layer on crystallographically oriented GaAs substrates. The cross-sectional TEM exhibited a sharp interface between the Ge epilayer and each orientation of the GaAs substrate as well as the Al{sub 2}O{sub 3} film and the Ge epilayer. The extracted valence band offset, {Delta}E{sub v}, values of Al{sub 2}O{sub 3} relative to (100), (110), and (111) Ge orientations using XPS measurement were 3.17 eV, 3.34 eV, and 3.10 eV, respectively. Using XPS data, variations in {Delta}E{sub v} related to the crystallographic orientation were {Delta}E{sub V}(110)Ge>{Delta}E{sub V}(100)Ge{>=}{Delta}E{sub V}(111)Ge and the conduction band offset, {Delta}E{sub c}, related to the crystallographic orientation was {Delta}E{sub c}(111)Ge>{Delta}E{sub c}(110)Ge>{Delta}E{sub c}(100)Ge using the measured {Delta}E{sub v}, bandgap of Al{sub 2}O{sub 3} in each orientation, and well-known Ge bandgap of 0.67 eV. These band offset parameters are important for future application of Ge-based p- and n-channel metal-oxide field-effect transistor design.

  4. Green (In,Ga,Al)P-GaP light-emitting diodes grown on high-index GaAs surfaces

    SciTech Connect (OSTI)

    Ledentsov, N. N., E-mail: nikolay.ledentsov@v-i-systems.com; Shchukin, V. A. [VI Systems GmbH, Hardenbergstr. 7, Berlin D-10623 (Germany); Lyytikäinen, J.; Okhotnikov, O. [Optoelectronics Research Centre, Tampere University of Technology, Tampere FI-33720 (Finland); Shernyakov, Yu. M.; Payusov, A. S.; Gordeev, N. Yu.; Maximov, M. V. [A. F. Ioffe Physical Technical Institute of the Russian Academy of Sciences, Politekhnicheskaya 26, St. Petersburg 194021 (Russian Federation); Schlichting, S.; Nippert, F.; Hoffmann, A. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36, Berlin D-10623 (Germany)

    2014-11-03T23:59:59.000Z

    We report on green (550–560?nm) electroluminescence (EL) from (Al{sub 0.5}Ga{sub 0.5}){sub 0.5}In{sub 0.5}P-(Al{sub 0.8}Ga{sub 0.2}){sub 0.5}In{sub 0.5}P double p-i-n heterostructures with monolayer-scale GaP insertions in the cladding layers and light-emitting diodes based thereupon. The structures are grown side-by-side on high-index and (100) GaAs substrates by molecular beam epitaxy. At moderate current densities (?500?A/cm{sup 2}), the EL intensity of the structures is comparable for all substrate orientations. Opposite to the (100)-grown strictures, the EL spectra of (211) and (311)-grown devices are shifted towards shorter wavelengths (?550?nm at room temperature). At high current densities (>1?kA/cm{sup 2}), a much higher EL intensity is achieved for the devices grown on high-index substrates. The integrated intensity of (311)-grown structures gradually saturates at current densities above 4?kA/cm{sup 2}, whereas no saturation is revealed for (211)-grown structures up to the current densities above 14?kA/cm{sup 2}. We attribute the effect to the surface orientation-dependent engineering of the GaP band structure, which prevents the escape of the nonequilibrium electrons into the indirect conduction band minima of the p-doped (Al{sub 0.8}Ga{sub 0.2}){sub 0.5}In{sub 0.5}P cladding layers.

  5. Tilt generation in step-graded In{sub x}Ga{sub 1-x}As metamorphic pseudosubstrate on a singular GaAs substrate using a low-temperature grown InGaP interlayer

    SciTech Connect (OSTI)

    Ghanad Tavakoli, Shahram; Hulko, Oksana; Thompson, David A. [Department of Engineering Physics, 1280 Main Street West, Hamilton, Ontario L8S 4 L7 (Canada)

    2008-05-15T23:59:59.000Z

    Metamorphic pseudosubstrates of In{sub 0.42}Ga{sub 0.58}As were grown by molecular beam epitaxy using step-graded In{sub x}Ga{sub 1-x}As buffer layers grown either directly on a (001) GaAs substrate or on a GaAs substrate overgrown with a layer of low-temperature grown In{sub 0.51}Ga{sub 0.49}P (LT-InGaP). The structures were examined using x-ray reciprocal space mapping to determine the characteristics of the pseudosubstrates and buffer layers. For the sample grown on the LT-InGaP layer, the pseudosubstrate exhibited an asymmetric tilt around [110] toward the [110] direction. Weak-beam dark-field electron imaging shows an imbalance of misfit dislocations with opposite sign Burgers vector. An explanation for this tilt is given and it is suggested that it may be responsible for the improved quality of epitaxial layers grown on such pseudosubstrates.

  6. Gas-source molecular-beam epitaxy of InGaP and GaAs on strained-relaxed Ge{sub x}Si{sub 1-x}/Si

    SciTech Connect (OSTI)

    Kuo, J.M.; Fitzgerald, E.A.; Xie, Y.H. [AT& T Bell Lab., Murray Hill, NJ (United States)] [and others] [AT& T Bell Lab., Murray Hill, NJ (United States); and others

    1993-05-01T23:59:59.000Z

    Lattice-matched GaAs and InGaP structures on strain-relieved Ge/graded GeSi/Si without increasing the threading dislocation density at the III-V/Ge interface have been successfully grown. The results show that exposure of the Ge surface to As{sub 2} produces a drastic change in the step structure of the Ge surface. Subsequent exposure to Ga and continuation of growth invariably produces three-dimensional growth and a high threading dislocation density at the GaAs/Ge interface. However, exposure of the Ge surface to Ga does not appear to change the Ge step structure, and subsequent growth of GaAs leads to near two-dimensional growth and no massive increase in threading dislocation density at the GaAs/Ge interface as in the case of As{sub 2} exposure. InGaP light-emitting homojunction diodes have been fabricated on the relaxed Ge/graded GeSi/Si. Room-temperature operation was achieved with a surface-emitting output power of {approximately} 10 mW/cm{sup 2}. The best dislocation density achieved was 5x10{sup 6}-10{sup 7} cm{sup {minus}2} in the InGaP/GaAs/Ge/graded GeSi/Si structure. 9 refs., 3 figs.

  7. Original article Effects of liming and gypsum regimes on chemical

    E-Print Network [OSTI]

    Boyer, Edmond

    chemistry. The natural soil was reconstituted in columns equipped with zero tension lysimeters. CaCO3, CaCO3 traitements sous forme CaCO3, CaCO3 + MgO et CaSO4, 2H2O sont appoités aux doses équivalentes en CaO de 0, 0

  8. Utilization of by-product gypsum in construction 

    E-Print Network [OSTI]

    Stephenson, Angela Lorraine

    1987-01-01T23:59:59.000Z

    as a by-product (called phosphogypsum) during acidulation of phosphate rock in the manufacture phosphoric acid. The sulfate is produced in either a dihydrate or a hemihydrate form depending on the operating conditions. Phosphogypsum produced... by Mobil Chemi- cal Company (Pasadena, Texas) is in the dihydrate form and was previously studied. Phosphogypsum produced by Occidental Chemical Company (White Springs, Florida), on the other hand, is produced in a hemihydrate form and transforms...

  9. Utilization of by-product gypsum in construction

    E-Print Network [OSTI]

    Stephenson, Angela Lorraine

    1987-01-01T23:59:59.000Z

    . Neutralization processes with NaOH and Ca(OH) & were studied and stabilization with commercial grade types of portland cement and fly ash was investigated (after different curing periods) to compare relative strengths as applied to road construction.... For phosphogypsum stabilized by portland cement, initial and intermediate stages of strength development obtained for the material, cured for 3 and 7 days at approximate pH levels of 4, 6, and 8 and cement contents of 34 and 64, yielded strengths which increase...

  10. Separation of Mercury from Flue Gas Desulfurization Scrubber Produced Gypsum

    SciTech Connect (OSTI)

    Hensman, Carl, E., P.h.D; Baker, Trevor

    2008-06-16T23:59:59.000Z

    Frontier Geosciences (Frontier; FGS) proposed for DOE Grant No. DE-FG02-07ER84669 that mercury control could be achieved in a wet scrubber by the addition of an amendment to the wet-FGD scrubber. To demonstrate this, a bench-scale scrubber and synthetic flue-gas supply was designed to simulate the limestone fed, wet-desulfurization units utilized by coal-fired power plants. Frontier maintains that the mercury released from these utilities can be controlled and reduced by modifying the existing equipment at installations where wet flue-gas desulfurization (FGD) systems are employed. A key element of the proposal was FGS-PWN, a liquid-based mercury chelating agent, which can be employed as the amendment for removal of all mercury species which enter the wet-FGD scrubber. However, the equipment design presented in the proposal was inadequate to demonstrate these functions and no significant progress was made to substantiate these claims. As a result, funding for a Phase II continuation of this work will not be pursued. The key to implementing the technology as described in the proposal and report appears to be a high liquid-to-gas ratio (L/G) between the flue-gas and the scrubber liquor, a requirement not currently implemented in existing wet-FGD designs. It may be that this constraint can be reduced through parametric studies, but that was not apparent in this work. Unfortunately, the bench-scale system constructed for this project did not function as intended and the funds and time requested were exhausted before the separation studies could occur.

  11. Molecular beam epitaxial growth of Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} topological insulators on GaAs (111) substrates: a potential route to fabricate topological insulator p-n junction

    SciTech Connect (OSTI)

    Zeng, Zhaoquan; Morgan, Timothy A.; Li, Chen; Hirono, Yusuke; Hu, Xian; Hawkridge, Michael E.; Benamara, Mourad; Salamo, Gregory J. [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States)] [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Fan, Dongsheng; Yu, Shuiqing [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States) [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Department of Electrical Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Zhao, Yanfei [International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871 (China)] [International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871 (China); Lee, Joon Sue [The Center for Nanoscale Science and Department of Physics, The Pennsylvania State University, University Park, PA 16802 (United States)] [The Center for Nanoscale Science and Department of Physics, The Pennsylvania State University, University Park, PA 16802 (United States); Wang, Jian [International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871 (China) [International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871 (China); The Center for Nanoscale Science and Department of Physics, The Pennsylvania State University, University Park, PA 16802 (United States); Wang, Zhiming M. [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States) [Arkansas Institute for Nanoscale Material Sciences and Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Engineering Research Center for Semiconductor Integrated Technology, Institute of Semiconductors, Chinese Academy of Science, Beijing 100083 (China)

    2013-07-15T23:59:59.000Z

    High quality Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} topological insulators films were epitaxially grown on GaAs (111) substrate using solid source molecular beam epitaxy. Their growth and behavior on both vicinal and non-vicinal GaAs (111) substrates were investigated by reflection high-energy electron diffraction, atomic force microscopy, X-ray diffraction, and high resolution transmission electron microscopy. It is found that non-vicinal GaAs (111) substrate is better than a vicinal substrate to provide high quality Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} films. Hall and magnetoresistance measurements indicate that p type Sb{sub 2}Te{sub 3} and n type Bi{sub 2}Te{sub 3} topological insulator films can be directly grown on a GaAs (111) substrate, which may pave a way to fabricate topological insulator p-n junction on the same substrate, compatible with the fabrication process of present semiconductor optoelectronic devices.

  12. Determination of bandgap states in p-type In[subscript 0.49]Ga[subscript 0.51]P grown on SiGe/Si and GaAs by deep level optical spectroscopy and deep level transient spectroscopy

    E-Print Network [OSTI]

    Gonza?lez, M.

    The presence and properties of traps in p-type In[subscript 0.49]Ga[subscript 0.51]P grown on low dislocation density, metamorphic Ge/SiGe/Si substrates and GaAs substrates were determined using deep level transient ...

  13. Quantitative analysis of compositional changes in InGaAs/InGaAsP quantum wells on GaAs induced by intermixing with a low temperature grown InGaP cap layer

    SciTech Connect (OSTI)

    Hulko, O.; Thompson, D. A.; Czaban, J. A.; Simmons, J. G. [Centre for Emerging Devices and Technologies (CEDT), McMaster University, Hamilton, Ontario L8S 4L8 (Canada)

    2006-08-07T23:59:59.000Z

    Energy-dispersive x-ray spectroscopy was used to analyze quantum well intermixing between an InGaAs quantum well (QW) and InGaAsP barriers grown on GaAs induced by a low temperature, molecular beam epitaxy grown, InGaP cap. This cap layer produces an enhanced blueshift of the photoluminescence (PL) wavelength following postgrowth annealing, and degradation of the PL signal. Cross-sectional transmission electron microscopy reveals modification of the whole structure, with formation of arsenic precipitates, broadening, and subsequent disappearance of the QWs in the capped structure. Uncapped samples are relatively unchanged. Increased phosphorus observed in the QW for capped structures confirms the diffusion of phosphorus from the P-rich cap.

  14. Room-temperature cw operation of InGaP/InGaAlP visible light laser diodes on GaAs substrates grown by metalorganic chemical vapor deposition

    SciTech Connect (OSTI)

    Ishikawa, M.; Ohba, Y.; Sugawara, H.; Yamamoto, M.; Nakanisi, T.

    1986-01-20T23:59:59.000Z

    Room-temperature cw operation for InGaP/InGaAlP double heterostructure (DH) laser diodes on GaAs substrates was achieved for the first time. The DH wafers were grown by low-pressure metalorganic chemical vapor deposition using methyl metalorganics. A lasing wavelength of 679 nm and a threshold current of 109 mA at 24C were obtained for an inner stripe structure laser diode with a 250- m-long and 7- m stripe geometry. The laser operated at up to 51C. The characteristic temperature T0 was 87 K at around room temperature. The lowest threshold current density, 5.0 kA/cmS, was obtained with a 20- m stripe width laser diode under room-temperature pulsed operation.

  15. Impact of stress relaxation in GaAsSb cladding layers on quantum dot creation in InAs/GaAsSb structures grown on GaAs (001)

    SciTech Connect (OSTI)

    Bremner, S. P. [School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney 2052 (Australia)] [School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney 2052 (Australia); Ban, K.-Y.; Faleev, N. N.; Honsberg, C. B. [School of Electrical, Computer and Energy Engineering, Ira A. Fulton Schools of Engineering, Solar Power Lab, Arizona State University, Tempe, Arizona 85287 (United States)] [School of Electrical, Computer and Energy Engineering, Ira A. Fulton Schools of Engineering, Solar Power Lab, Arizona State University, Tempe, Arizona 85287 (United States); Smith, D. J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States)] [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States)

    2013-09-14T23:59:59.000Z

    We describe InAs quantum dot creation in InAs/GaAsSb barrier structures grown on GaAs (001) wafers by molecular beam epitaxy. The structures consist of 20-nm-thick GaAsSb barrier layers with Sb content of 8%, 13%, 15%, 16%, and 37% enclosing 2 monolayers of self-assembled InAs quantum dots. Transmission electron microscopy and X-ray diffraction results indicate the onset of relaxation of the GaAsSb layers at around 15% Sb content with intersected 60° dislocation semi-loops, and edge segments created within the volume of the epitaxial structures. 38% relaxation of initial elastic stress is seen for 37% Sb content, accompanied by the creation of a dense net of dislocations. The degradation of In surface migration by these dislocation trenches is so severe that quantum dot formation is completely suppressed. The results highlight the importance of understanding defect formation during stress relaxation for quantum dot structures particularly those with larger numbers of InAs quantum-dot layers, such as those proposed for realizing an intermediate band material.

  16. Evidence of a bacterial carbonate coating on plaster samples subjected to the Calcite Bioconcept biomineralization technique

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    made of concrete as well as historic buildings made of stone or brick. These porous materials on concrete and on limestone samples in an aqueous environment. However, the carbonate production was measured and biological) [1, 2]. In all cases, water transfer within the whole volume of the porous media is the common

  17. Anomalous diffusion of Ga and As from semi-insulating GaAs substrate into MOCVD grown ZnO films as a function of annealing temperature and its effect on charge compensation

    SciTech Connect (OSTI)

    Biswas, Pranab; Banerji, P., E-mail: pallab@matsc.iitkgp.ernet.in [Materials Science Centre, Indian Institute of Technology, Kharagpur 721 302 (India); Halder, Nripendra N. [Advanced Technology Development Centre, Indian Institute of Technology, Kharagpur 721 302 (India)] [Advanced Technology Development Centre, Indian Institute of Technology, Kharagpur 721 302 (India); Kundu, Souvik [School of Electrical Engineering and Computer Science, Oregon State University, 1148 Kelley Engineering Center, Corvallis, OR 97331–5501 (United States)] [School of Electrical Engineering and Computer Science, Oregon State University, 1148 Kelley Engineering Center, Corvallis, OR 97331–5501 (United States); Shripathi, T.; Gupta, M. [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452 001 (India)] [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452 001 (India)

    2014-05-15T23:59:59.000Z

    The diffusion behavior of arsenic (As) and gallium (Ga) atoms from semi-insulating GaAs (SI-GaAs) into ZnO films upon post-growth annealing vis-à-vis the resulting charge compensation was investigated with the help of x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy. The films, annealed at 600 ºC and 700 ºC showed p-type conductivity with a hole concentration of 1.1 × 10{sup 18} cm{sup ?3} and 2.8 × 10{sup 19} cm{sup ?3} respectively, whereas those annealed at 800 ºC showed n-type conductivity with a carrier concentration of 6.5 × 10{sup 16} cm{sup ?3}. It is observed that at lower temperatures, large fraction of As atoms diffused from the SI-GaAs substrates into ZnO and formed acceptor related complex, (As{sub Zn}–2V{sub Zn}), by substituting Zn atoms (As{sub Zn}) and thereby creating two zinc vacancies (V{sub Zn}). Thus as-grown ZnO which was supposed to be n-type due to nonstoichiometric nature showed p-type behavior. On further increasing the annealing temperature to 800 ºC, Ga atoms diffused more than As atoms and substitute Zn atoms thereby forming shallow donor complex, Ga{sub Zn}. Electrons from donor levels then compensate the p-type carriers and the material reverts back to n-type. Thus the conversion of carrier type took place due to charge compensation between the donors and acceptors in ZnO and this compensation is the possible origin of anomalous conduction in wide band gap materials.

  18. hal-00194999,version1-8Dec2007 Arsenic uptake by gypsum and calcite

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    of contaminants by solid phases is relevant to many issues in environmental science as this process can remove to distinguish As substituted within the structure from that adsorbed on the surface of both minerals. Results of As into the C crystallographic site. Key words: arsenic, minerals, simulation, diffraction, EXAFS 1

  19. The detrimental effects of salinity on rooting of coleus cuttings and their alleviation with gypsum

    E-Print Network [OSTI]

    Janssen, Antonius Hendrick

    1981-01-01T23:59:59.000Z

    . The effect of NaC1 on root number and color intensity of the foliage were not altered by the addition of CaSO . The beneficial effects of CaS04 cou1d not be demonstrated in a peat-styrafoam medium. Acknowledgements I would like to express my sincere... Ca/Na ratios for the NaC1:Ca504 solutions 5 Electrical conductivities (E. C. ) of 2 KNO solutions with i ncreasing CaS04 concent/ations 6 The effects of pH and peat extract on rooting of 'Big Red' cuttings . Page 13 15 44 45 56 LIST...

  20. Characterization of metallic studs used in gypsum board single frame walls

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    connections modeled by punctual springs defined by its translational stiffness located at the screws position filled by absorbing material to improve the acoustic performance. When the double wall is mounted between the two leaves is considered as point connections modeled by punctual springs located

  1. Socio-economic and Environmental Impact Analysis of Khothagpa Gypsum Mine

    E-Print Network [OSTI]

    Galay, Karma

    2008-01-01T23:59:59.000Z

    : Close-up view of the scar B. Health impacts A few interviewees of this study reported that the frequency of occurrence of diseases such as cold and cough which people believe are commonly caused by presence of more dusts, is more now as compared...

  2. Magnetic resonance studies of cement based materials in inhomogeneous magnetic fields

    SciTech Connect (OSTI)

    Boguszynska, Joanna [Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, Poznan (Poland); Brown, Marc C.A. [School of Physical Sciences, University of Kent, Canterbury, Kent, CT2 7NR (United Kingdom); McDonald, Peter J. [School of Electronics and Physical Sciences, University of Surrey, Surrey, GU2 7XH (United Kingdom)]. E-mail: p.mcdonald@surrey.ac.uk; Mitchell, Jonathan [School of Electronics and Physical Sciences, University of Surrey, Surrey, GU2 7XH (United Kingdom); Mulheron, Mike [School of Engineering, University of Surrey, Surrey, GU2 7XH (United Kingdom); Tritt-Goc, Jadwiga [Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, Poznan (Poland); Verganelakis, Dimitris A. [Department of Chemical Engineering, University of Cambridge, Cambridge, CB2 3RA (United Kingdom)

    2005-10-01T23:59:59.000Z

    Single-sided magnets give hope that Nuclear Magnetic Resonance (NMR) might in future be used for in situ characterisation of hydration and water transport in the surface layers of concrete slabs. Towards that end, a portable NMR-MOUSE (MObile Universal Surface Explorer) has been used to follow the hydration of gypsum based plaster, a Portland cement paste and concrete mortar. The results compare favourably to those obtained using a standard laboratory bench-top spectrometer. Further, stray field imaging (STRAFI) based methods have been used with embedded NMR detector coils to study water transport across a mortar/topping interface. The measured signal amplitudes are found to correlate with varying sample conditions.

  3. Separation of flue-gas scrubber sludge into marketable products. Second quarterly technical progress report, December 1, 1993--February 28, 1994 (Quarter No. 2)

    SciTech Connect (OSTI)

    Kawatra, S.K.; Eisele, T.C.

    1994-03-01T23:59:59.000Z

    To reduce their sulfur emissions, many coal-fired electric power plants use wet flue-gas scrubbers. These scrubbers convert sulfur oxides into solid sulfate and sulfite sludge, which must then be disposed of This sludge is a result of reacting limestone with sulfur dioxide to precipitate calcium sulfite and calcium sulfate. It consists of calcium sulfite (CaSO{sub 3}{lg_bullet}0.5H{sub 2}0), gypsum (CaSO{sub 4}{lg_bullet}2H{sub 2}0), and unreacted limestone (CaCO{sub 3}) or lime (Ca(OH){sub 2}), with miscellaneous objectionable impurities such as iron oxides; silica; and magnesium, sodium, and potassium oxides or salts. Currently, the only market for scrubber sludge is for manufacture of gypsum products, such as wallboard and plaster, and for cement. However, the quality of the raw sludge is often not high enough or consistent enough to satisfy manufacturers, and so the material is difficult to sell. This project is developing a process that can produce a high-quality calcium sulfite or gypsum product while keeping process costs low enough that the material produced will be competitive with that from other, more conventional sources. This purification will consist of minimal-reagent froth flotation, using the surface properties of the particles of unreacted limestone to remove them and their associated impurities from the material, leaving a purified gypsum or calcium sulfite product. The separated limestone will be a useful by-product, as it can be recycled to the scrubber, thus boosting the limestone utilization and improving process efficiency. Calcium sulfite will then be oxidized to gypsum, or separated as a salable product in its own right from sludges where it is present in sufficient quantity. The main product of the process will be either gypsum or calcium sulfite, depending on the characteristics of the sludge being processed. These products will be sufficiently pure to be easily marketed, rather that being landfilled.

  4. Gypsum scale formation on a heated copper plate under natural convection conditions and produced water remediation technologies review

    E-Print Network [OSTI]

    Mirhi, Mohamad H. (Mohamad Hussein)

    2013-01-01T23:59:59.000Z

    Scaling or crystallization fouling of unwanted salts is one of the most challenging and expensive problems encountered in different applications such as heat exchangers and thermal water treatment technologies. Formation ...

  5. Using gypsUm and Other CalCiUm amendments in sOUthwestern sOils

    E-Print Network [OSTI]

    Sanderson, Mike

    and stability, the primary features of soil structure, are two of the most important manageable soil and size, is shown in Table 1. In this table the flocculating power of Na+ is assigned a value of 1 of these weak and strong flocculators. This can be done by calculating the Sodium Adsorption Ratio (SAR), where

  6. Teaching Direct Marketing and Small Farm Viability: Resources for Instructors, 2nd Edition. Unit 6 - Building Resilience: Small Farm Planning and Operations

    E-Print Network [OSTI]

    2015-01-01T23:59:59.000Z

    Soil Tests Seed Amendments Compost Manure Gypsum Kelp MealSoil Tests Seed Amendments Compost Manure Gypsum Kelp Meal

  7. Liquid phase epitaxial growth of GaAs

    SciTech Connect (OSTI)

    Wynne, D I [Univ. of California, Berkeley, CA (United States). Materials Science and Mineral Engineering

    1997-10-01T23:59:59.000Z

    Research into new semiconductor materials for measurement of electromagnetic radiation over a wide range of energies has been an active field for several decades. There is a strong desire to identify and develop new materials which can lead to improved detectors. Such devices are expected to solve problems that cannot be solved using the semiconductor materials and device structures which have been traditionally used for radiation detection. In order for a detector which is subjected to some type of irradiation to respond, the radiation must undergo an interaction with the detector. The net result of the radiation interaction in a broad category of detectors is the generation of mobile electric charge carriers (electrons and/or holes) within the detector active volume. This charge is collected at the detector contacts and it forms the basic electrical signal. Typically, the collection of the charge is accomplished through the imposition of an electric field within the detector which causes the positive and/or negative charges created by the radiation to flow in opposite directions to the contacts. For the material to serve as a good radiation detector, a large fraction (preferably 100%) of all carriers created by the interacting incident radiation must be collected. Charge trapping by deep level impurities and structural defects can seriously degrade detector performance. The focus of this thesis is on far infrared and X-ray detection. In X-ray detector applications of p-I-n diodes, the object is to measure accurately the energy distribution of the incident radiation quanta. One important property of such detectors is their ability to measure the energy of individual incident photons with high energy resolution.

  8. Incorporation of aqueous reaction kinetics and biodegradation into TOUGHREACT: Application of a multi-region model to hydrobiogeoChemical transport of denitrification and sulfate reduction

    E-Print Network [OSTI]

    Xu, Tianfu

    2008-01-01T23:59:59.000Z

    Region: quartz calcite gypsum goethite Hydro- Region: Na + ,minerals gypsum and goethite were assumed to be initiallyChem-Region, Fe generated from goethite dissolution and HS

  9. Edinburgh College of Art : cast collection and architecture 

    E-Print Network [OSTI]

    Stoica, Ruxandra-Iulia; Stewart, Margaret

    2012-01-01T23:59:59.000Z

    The Edinburgh Cast Collection comprises 265 plaster casts of Antique, Renaissance, and Gothic statues, bas reliefs, and architectural passages held at the Edinburgh College of Art and the University of Edinburgh. The plaster casts at the Edinburgh...

  10. Accumulation and replacement of exchangeable sodium in soils of Southeast Texas under turfgrass and its effect on soil infiltration rate

    E-Print Network [OSTI]

    Aydemir, Salih

    1996-01-01T23:59:59.000Z

    gypsum application. 34 TABLE Page 10 Mean of extractable bases at site 1 for 20-30 cm depth before gypsum application and 9 wk and 36 wk rdter gypsum application. 35 Mean of extractable bases at site 2 for 0-10 cm depth before gypsum application... and 9 wk and 36 wk after gypsum application. 36 12 Mean of extractable bases at site 2 for 10-20 cm depth before gypsum application and 9 wk and 36 wk after gypsum application. 38 13 Mean of extractable bases at site 2 for 20-30 cm depth before...

  11. Excitation-Dependent Recombination and Diffusion Near an Isolated Dislocation in GaAs

    SciTech Connect (OSTI)

    Gfroerer, T. H.; Crowley, C. M.; Read, C. M.; Wanlass, M. W.

    2012-06-01T23:59:59.000Z

    In low-magnification, plan-view photoluminescence images of a nominally lattice-matched, undoped GaAs/GaInP heterostructure, we observe a random distribution of isolated dark spots. We attribute the dark spots to crystal dislocations, where nonradiative recombination is augmented by transitions utilizing defect-related energy levels between the conduction and valence bands. We note that, when the laser excitation intensity is reduced, the darkened regions expand. At lower excitation, the density of photogenerated electrons and holes is reduced, and they are more likely to reach the defective region before encountering a partner for radiative recombination. When we model the behavior with a simulation that allows for Laplacian diffusion and defect-related recombination only through mid-bandgap energy levels, we do not obtain good agreement between experimental and simulated images. But if we allow for an arbitrary distribution of defect levels, such that the occupation of the levels and bands can change independently, we have more flexibility for fitting the density-dependent recombination rates. The more sophisticated model produces results that are more consistent with experimental images.

  12. Antimonide-Based Long-Wavelength Lasers on GaAs Substrates

    SciTech Connect (OSTI)

    KLEM,JOHN F.; Blum, O.

    2000-08-17T23:59:59.000Z

    We have investigated the use of GaAsSb in edge-emitting laser active regions, in order to obtain lasing near 1.3 {micro}m. Single quantum well GaAsSb devices display electroluminescence at wavelengths as long as 1.34 {micro}m, but substantial blueshifts occur under high injection conditions. GaAsSb single quantum well edge emitters have been obtained which lase at 1.275 {micro}m with a room-temperature threshold current density as low as 535 A/cm{sup 2}. Modification of the basic GaAsSb/GaAs structure with the addition of InGaAs layers results in a strongly type-II band alignment which can be used to further extend the emission wavelength of these devices. Using GaAsSb/InGaAs active regions, lasers emitting at 1.17 {micro}m have been obtained with room-temperature threshold current densities of 120 A/cm{sup 2}, and devices operating at 1.29 {micro}m have displayed thresholds as low as 375 A/cm{sup 2}. Characteristic temperatures for devices employing various GaAsSb-based active regions have been measured to be 60-73 K.

  13. E-Print Network 3.0 - adsorbate covered gaas1 Sample Search Results

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    ; Physics ; Materials Science 82 Terahertz Time-Domain Spectroscopy Study of Silica Aerogels and Adsorbed Molecular Jiangquan Zhang and D. Grischkowsky* Summary: that the...

  14. Magnetostructure of MnAs on GaAs revisited E. Bauer,1,2

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    introduced a model in which the crystal changed from a high spin state in the phase to a low spin state change during the phase transition is connected with a change of the sign of the exchange constant via material. hal-00193844,version1-4Dec2007 #12;3 FIG. 1. Structure of MnAs. (a) Hexagonal phase (NiAs type

  15. Recent improvements in materials for thin GaAs and multibandgap solar cells

    SciTech Connect (OSTI)

    Benner, J.P.

    1985-05-01T23:59:59.000Z

    The High Efficiency Concepts Program at SERI supports research on III-V compound semiconductors with the objective of achieving the maximum attainable photovoltaic conversion efficiencies for terrestrial solar electric power. The outcome of this research may also affect the future of space photovoltaic cells. While the interest in thin-film, high-efficiency solar cells for terrestrial applications is driven principally by consideration of system costs, such cells would also improve the power density of space power arrays.

  16. Superluminescent damping of relaxation resonance in the modulation response of GaAs lasers

    SciTech Connect (OSTI)

    Lau, K.Y.; Ury, I.; Bar-Chaim, N.; Harder, C.; Yariv, A.

    1983-08-15T23:59:59.000Z

    It is demonstrated experimentally that the intrinsic modulation response of injection lasers can be modified by reducing mirror reflectivities, which leads to suppression of relaxation oscillation resonance and a reduction of nonlinear distortions up to multi-GHz frequencies. A totally flat response with a 3-dB bandwidth of 5 GHz was obtained using antireflection coated buried heterostructure lasers fabricated on a semi-insulating substrate. Harmonic distortions were below 40 dB within the entire 3-dB bandwidth. These results are in accord with theoretical predictions based on an analysis which include the effects of superluminescence in the laser cavity.

  17. Longitudinal mode spectrum of GaAs injection lasers under high-frequency microwave modulation

    SciTech Connect (OSTI)

    Lau, K.Y.; Harder, C.; Yariv, A.

    1983-10-01T23:59:59.000Z

    Experimental observations of the lasing spectrum of a single mode semiconductor laser under continuous microwave modulation reveal that the lasing spectrum is apparently locked to a single longitudinal mode for optical modulation depths up to approx.80%, beyond which the lasing spectrum becomes multimoded, whose envelope width increases very rapidly with further increase in modulation depth. These results are satisfactorily explained by a theoretical treatment which enables one to predict the dynamic lasing spectrum of a laser from its cw lasing spectra at various output powers.

  18. Carbon-doped GaAs single junction solar microcells grown in multilayer epitaxial assemblies

    E-Print Network [OSTI]

    Li, Xiuling

    for the degraded contact properties and photovoltaic performance, resulting from prolonged thermal treatmentsAs solar cells,6 however, the photovoltaic performance showed a systematic degradation betwe of photovoltaic performance compared to zinc-doped systems due to the lack of mobile dopants while a slight

  19. Carbon-doped GaAs single junction solar microcells grown in multilayer epitaxial assemblies

    E-Print Network [OSTI]

    Rogers, John A.

    responsible for the degraded contact properties and photovoltaic performance, resulting from prolonged thermalAs solar cells,6 however, the photovoltaic performance showed a systematic degradation between device uniformity of photovoltaic performance compared to zinc-doped systems due to the lack of mobile dopants while

  20. The design of GaAs HEMT and HBT Bessel-type transimpedance amplifiers

    E-Print Network [OSTI]

    Adeyemi, Oluwafemi Ibukunoluwa

    2007-04-25T23:59:59.000Z

    chips at low cost, using relatively cheap semiconductor processes. The optical preamplifier (transimpedance amplifier) receives optical information and converts it to a useful electrical form. It must operate at high speed, contribute little distortion...

  1. activated si-gaas high-voltage: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Summary: ??This thesis is concerned with developing a new approach to high voltage transformers condition monitoring, which involve partial discharge (PD) measurement and...

  2. Non-Collinear Paramagnetism of a GaAs Two-Dimensional Hole System

    E-Print Network [OSTI]

    Yeoh, L. A.; Srinivasan, A.; Klochan, O.; Winkler, R.; Zülicke, U.; Simmons, M. Y.; Ritchie, D. A.; Pepper, M.; Hamilton, A. R.

    2014-12-03T23:59:59.000Z

    to manipulate the perpen- dicular spin polarization without coupling to the orbital momentum, paving the way for more detailed studies and applications of non-collinear magnetic responses in low- dimensional hole systems. We thank A. Edgar, T. Li, O. P. Sushkov...

  3. Corrosion-induced degradation of GaAs PHEMTs under operation in high humidity conditions

    E-Print Network [OSTI]

    Hisaka, Takayuki

    We have comprehensively investigated the degradation mechanism of AlGaAs/InGaAs pseudomorphic high-electron-mobility transistors (PHEMTs) under operation in high humidity conditions. PHEMTs degradation under high humidity ...

  4. Modifications du travail de sortie des surfaces clives de GaAs, lies au refroidissement

    E-Print Network [OSTI]

    Boyer, Edmond

    les positions energetiques des etats de surface. Cette idee a ete reprise et developpee par L. K experimentaux ne posent pas de probleme majeur [6], 1'exp6rimentation, delicate, conduit a se poser la question

  5. Fourier spectroscopy of individual nitrogen impurity centers in GaAs

    SciTech Connect (OSTI)

    Ikezawa, Michio [PRESTO-JST, JST, Kawaguchi, Japan and Institute of Physics, University of Tsukuba, Tsukuba (Japan); Zhang, Liao; Mori, Tatsuya; Masumoto, Yasuaki [Institute of Physics, University of Tsukuba, Tsukuba (Japan); Sakuma, Yoshiki; Sakoda, Kazuaki [National Institute for Materials Science, Tsukuba (Japan)

    2013-12-04T23:59:59.000Z

    We report on the measurement of the exciton homogeneous linewidth in nitrogen impurity centers in GaAs:N. Fourier spectroscopy on a single center revealed a long coherence time over 300 ps at low temperature. The narrowest linewidth obtained at liquid helium temperature is 3.5 ?eV, which is comparable with that of semiconductor quantum dots. The linewidth increases with increasing temperature, showing a thermally activated behavior with activation energies of 2?5 meV.

  6. Free carrier induced spectral shift for GaAs filled metallic hole arrays

    E-Print Network [OSTI]

    New Mexico, University of

    References and links 1. J. M. Luther, P. K. I. Jain, T. Ewers, and A. P. Alivisatos, "Localized surface

  7. Double Power Output for GaAs Solar Cells Embedded in Luminescent Waveguides

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625govInstrumentstdmadapInactiveVisitingContract ManagementDiscovering HowAna Moore Anne Jones DevensforDouble

  8. UNIVERSITY OF CONNECTICUT HEALTH CENTER ASBESTOS AWARENESS POLICY

    E-Print Network [OSTI]

    Kim, Duck O.

    asbestos include roofing, walls and ceilings, panels and partitions, boilers and water tanks, heaters, flues and tank insulation, decorative plaster finishes, car parts, sprayed on coatings and insulation

  9. Experiential Learning Spring Courses 2009 Note: This list emphasizes courses with few prerequisites but students should refer to the Bulletin

    E-Print Network [OSTI]

    Fraden, Seth

    to the very basics of 3D modeling with Cinema4D, rapid prototyping (3D printing with the Zcorp plaster printer

  10. Wisconsin Research with Dick Wolkowski, Birl Lowery, Ana Tapsieva

    E-Print Network [OSTI]

    Balser, Teri C.

    , UW-Madison Meghan Buckley UW-Stevens Point #12;What is FGD Gypsum Flue Gas Desulfurization Gypsum application to crops · Avoid landfilling #12;Land Application Considerations Source: Ohio State Univ. Pub. ANR

  11. E-Print Network 3.0 - ash management regulations Sample Search...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    REGULATOR IN PORTLAND CEMENT 6 Traditionally about 3 to 5% gypsum is inter... of clean-coal ash (CCA) was used to replace gypsum as a setting time regulator and mineral...

  12. Janet and Grant Brians: Brians Ranch

    E-Print Network [OSTI]

    Farmer, Ellen

    2010-01-01T23:59:59.000Z

    Brians: Well, putting on compost and gypsum have been two ofback in the soil, and compost and things. But we didn’tthen putting gypsum and compost in, gradually it’s getting

  13. Lifecycle Assessment of Beijing-Area Building Energy Use and Emissions: Summary Findings and Policy Applications

    E-Print Network [OSTI]

    Aden, Nathaniel

    2010-01-01T23:59:59.000Z

    Production Intensity Material kg/m Section Steel Steel Bar Aluminum Cement Glass Gypsum board* Acrylic Rubber -

  14. Clim. Past Discuss., 6, 627657, 2010 www.clim-past-discuss.net/6/627/2010/

    E-Print Network [OSTI]

    Utrecht, Universiteit

    ) records reveal a prominent 3.4 m thick basic cyclicity of alternating playa gypsum and dry mudflat red

  15. MOUSSES MINERALES A PERFORMANCES OPTIMISEES

    E-Print Network [OSTI]

    Boyer, Edmond

    of these gypsum foams are then assessed and compared to the ones obtained for cellular and hemp concrete. Physical

  16. Dept. of Sol Science, UW-Madison/UW-Extension, 1525 Observatory Dr., Madison, WI 53706/608-262-0485 November 2010 Issue #2 2010

    E-Print Network [OSTI]

    Balser, Teri C.

    /608-262-0485 ____________________________________________________________________________________ November 2010 Issue #2 2010 Using Flue Gas Desulfurization (FGD) Gypsum in Wisconsin Dick Wolkowski, Birl plants burn low S coal and some have installed flue gas scrubbers to reduce sulfur emissions. Use of a wet scrubber results in the byproduct flue gas desulfurization (FGD) gypsum. FGD gypsum is created

  17. By-Products Utilization

    E-Print Network [OSTI]

    Wisconsin-Milwaukee, University of

    that over 80,000 tons of gypsum wallboard is disposed each year in Wisconsin from new construction.I. has recently established a technology of using a gypsum-containing cementitious material from coal gypsum wallboard, Class C fly ash, and cement will be used as a cementitious material; and, the mixture

  18. Enhanced Performance of Small GaAs Solar Cells via Edge and Surface Passivation with Trioctylphosphine Sulfide

    E-Print Network [OSTI]

    Atwater, Harry

    % (absolute), even after a rinse in toluene to remove all but a few monolayers of TOP:S, confirming sidewall surfaces are passivated by heterojunction windows but whose edges are exposed. In very small cells, the larger fraction of exposed sidewall surface area causes an increase of recombination dark current

  19. Direct amplitude modulation of short-cavity GaAs lasers up to X-band frequencies

    SciTech Connect (OSTI)

    Lau, K.Y.; Bar-Chaim, N.; Ury, I.; Harder, C.; Yariv, A.

    1983-07-01T23:59:59.000Z

    Experimental and theoretical studies indicate that a high-frequency laser with bandwidths up to X-band frequencies (> or approx. =10 GHz) should be one having a short cavity with a window structure, and preferably operating at low temperatures. These designs would accomplish the task of shortening the photon lifetime, increasing the intrinsic optical gain, and increasing the internal photon density without inflicting mirror damage. A modulation bandwidth of >8 GHz has been achieved using a 120-..mu..m laser without any special window structure at room temperature.

  20. Fabrication of wideband optoelectronic differential amplifier using a balanced receiver on a semi-insulating GaAs substrate

    E-Print Network [OSTI]

    Choi, Kyoo Nam

    1989-01-01T23:59:59.000Z

    photocurrent flow- ing between the electrodes Iz, given by Is = (oE)WD = (qIr?nE)WD = (qnVs)WD I, = q( h )( L )=I ( L ) P~ p rE p rE (27) (26) 14 where I s is the primary photocurrent and E is the electric field inside the photocon- ductor. Also... of inductive(capacitive circuit elements and simulate overall output response. Design of Balanced Receiver It will be necessary to have two photo-conductive gaps, an output terminal pad and three pads to apply dual DC biases (positive, neutral, negative...

  1. Fabrication of wideband optoelectronic differential amplifier using a balanced receiver on a semi-insulating GaAs substrate 

    E-Print Network [OSTI]

    Choi, Kyoo Nam

    1989-01-01T23:59:59.000Z

    bandwidth. The monolithic receiver design described here has greatly reduced these undesirable effects and allowed multi-gigshertz performance. Balanced receivers have been fabricated with photoconductive gap widths of 5 pm and 3 Izrn... and supplies and to Jim Gardner for laser scribing and reticle fabrication support. I would especially like to thank Victor Swenson for his help in diagnosing and repairing the many equipment problems and instructions on equipment operation. I would also...

  2. Calculations of bound and resonant electronic states for the GaAs (111) (2x2) reconstructed surface

    E-Print Network [OSTI]

    Blount, Samuel Stephen

    1985-01-01T23:59:59.000Z

    ) l'or k = ]7. Plot of p]e, (k, E) for k = 18. 7'lot of p]?(k, E) for k = ]1). Plot of p]?(k, E) for k = 20. Plot of p], (k, E) for k = 21. Plot of p]?(k, E) for k = (0. 0000, 0, 0000), ? ]3eV. & E - ? Bel', 22 (0. 0000, 0, 0000), ? SeV & E.... 1426, 0. 0000), ? BeV. & E & ? 3e]~'. (0. 1426, 0. 0000), ? 3eV. & E - 2eV. 35 (0. 1784, 0, 0000), ? 13 e V. & E & ? Be V. . 37 (0. 1784, 0. 0000), ? SeV. & E & ? 3eV. . 38 (0. 1784, 0. 0000), ? 3eV. & E & 2eV. . . . 3g 22 Plot of p]?(k, E) for k...

  3. Hot-Electron Thermocouple and the Diffusion Thermopower of Two-Dimensional Electrons in GaAs

    E-Print Network [OSTI]

    Eisenstein, Jim

    of Technology, Pasadena, California 91125, USA 2 Sandia National Laboratories, Albuquerque, New Mexico 87185.1103/PhysRevLett.103.046807 PACS numbers: 73.50.Lw, 72.20.Pa, 73.63.Hs The thermoelectric properties of low. The resulting phonon wind exerts a drag force on the electron gas which leads to a thermoelectric voltage

  4. Effective masses for small nitrogen concentrations in InGaAsN alloys on GaAs

    SciTech Connect (OSTI)

    JONES,ERIC D.; ALLERMAN,ANDREW A.; KURTZ,STEVEN R.; FRITZ,IAN J.; MODINE,NORMAND A.; SIEG,ROBERT M.; BAJAJ,K.K.; TOZER,S.W.; WEI,X.

    2000-05-11T23:59:59.000Z

    The variation of the value of the linewidth of an excitonic transition in InGaAsN alloys (1% and 2% nitrogen) as a function of hydrostatic pressure using photoluminescence spectroscopy is studied at 4K. The excitonic linewidth increases as a function of pressure until about 100 kbar after which it tends to saturate. This pressure dependent excitonic linewidth is used to derive the pressure variation of the exciton reduced mass using a theoretical formalism based on the premise that the broadening of the excitonic transition is caused primarily by compositional fluctuations in a completely disordered alloy. The linewidth derived ambient pressure masses are compared and found to be in agreement with other mass measurements. The variation of this derived mass is compared with the results from a nearly first-principles approach in which calculations based on the local density approximation to the Kohn-Sham density functional theory are corrected using a small amount of experimental input.

  5. Effect of quantum dot position and background doping on the performance of quantum dot enhanced GaAs solar cells

    SciTech Connect (OSTI)

    Driscoll, Kristina, E-mail: kmdsps@rit.edu; Bennett, Mitchell F.; Polly, Stephen J.; Forbes, David V.; Hubbard, Seth M., E-mail: smhsps@rit.edu [NanoPower Research Laboratories, Rochester Institute of Technology, Rochester, New York (United States)

    2014-01-13T23:59:59.000Z

    The effect of the position of InAs quantum dots (QD) within the intrinsic region of pin-GaAs solar cells is reported. Simulations suggest placing the QDs in regions of reduced recombination enables a recovery of open-circuit voltage (V{sub OC}). Devices with the QDs placed in the center and near the doped regions of a pin-GaAs solar cell were experimentally investigated. While the V{sub OC} of the emitter-shifted device was degraded, the center and base-shifted devices exhibited V{sub OC} comparable to the baseline structure. This asymmetry is attributed to background doping which modifies the recombination profile and must be considered when optimizing QD placement.

  6. Perturbation of Au-assisted planar GaAs nanowire growth by p-type dopant impurities

    E-Print Network [OSTI]

    Li, Xiuling

    . Mårtensson, J. Trägårdh, C. Larsson, M. Rask, D. Hessman, L. Samuelson, and J. Ohlsson, "Monolithic GaAs/InGaP

  7. Epitaxial growth of Cu,,In,Ga...Se2 on GaAs,,110... and A. Rockett

    E-Print Network [OSTI]

    Rockett, Angus

    . INTRODUCTION The Cu(In, Ga)Se2 CIGS absorber layer in a recent record-efficiency CIGS solar cell1 has a 220.13 Commercially supplied ``epi-ready'' liquid- encapsulated Czo

  8. Growth Mechanism and Electronic Structure of Zn3P2 on the Ga-Rich GaAs(001) Surface

    E-Print Network [OSTI]

    Atwater, Harry

    as well as the potential for low-cost, thin-film fabrication make Zn3P2 a promising active material Zn3P2 films on III-V substrates unlocks a promising pathway toward high-efficiency, earth-abundant photovoltaic devices fabricated on reusable, single-crystal templates. The detailed chemical, structural

  9. How to recycle asbestos containing materials (ACM)

    SciTech Connect (OSTI)

    Jantzen, C.M.

    2000-04-11T23:59:59.000Z

    The current disposal of asbestos containing materials (ACM) in the private sector consists of sealing asbestos wetted with water in plastic for safe transportation and burial in regulated land fills. This disposal methodology requires large disposal volumes especially for asbestos covered pipe and asbestos/fiberglass adhering to metal framework, e.g. filters. This wrap and bury technology precludes recycle of the asbestos, the pipe and/or the metal frameworks. Safe disposal of ACM at U.S. Department of Energy (DOE) sites, likewise, requires large disposal volumes in landfills for non-radioactive ACM and large disposal volumes in radioactive burial grounds for radioactive and suspect contaminated ACM. The availability of regulated disposal sites is rapidly diminishing causing recycle to be a more attractive option. Asbestos adhering to metal (e.g., pipes) can be recycled by safely removing the asbestos from the metal in a patented hot caustic bath which prevents airborne contamination /inhalation of asbestos fibers. The dissolution residue (caustic and asbestos) can be wet slurry fed to a melter and vitrified into a glass or glass-ceramic. Palex glasses, which are commercially manufactured, are shown to be preferred over conventional borosilicate glasses. The Palex glasses are alkali magnesium silicate glasses derived by substituting MgO for B{sub 2}O{sub 3} in borosilicate type glasses. Palex glasses are very tolerant of the high MgO and high CaO content of the fillers used in forming asbestos coverings for pipes and found in boiler lashing, e.g., hydromagnesite (3MgCO{sub 3} Mg(OH){sub 2} 3H{sub 2}O) and plaster of paris, gypsum (CaSO{sub 4}). The high temperate of the vitrification process destroys the asbestos fibers and renders the asbestos non-hazardous, e.g., a glass or glass-ceramic. In this manner the glass or glass-ceramic produced can be recycled, e.g., glassphalt or glasscrete, as can the clean metal pipe or metal framework.

  10. The utilization of flue gas desulfurization waste by-products in construction brick 

    E-Print Network [OSTI]

    Berryman, Charles Wayne

    1992-01-01T23:59:59.000Z

    Unconfined Compressive Strength and Density Comparisons of Gypsum Hemihydrate with Various Inductions of Fly Ash 16 Unconfined Compressive Strength and Density Comparisons Using Various Types of Bottom Ashes 18 Optimum Temperature to Calcine Dihydrate... Gypsum to Hemihydrate Gypsum 21 Optimum Time to Calcine Dihydrate to Hemihydrate 22 Unconfined Compressive Strength and Density Comparisons for Hemihydrate Subjected to Various Size Sieves 25 Temperature of Hemihydrate during Hydration versus Time...

  11. The effect of inclusions in brittle material

    E-Print Network [OSTI]

    Janeiro, Raymond Pinho

    2009-01-01T23:59:59.000Z

    This thesis experimentally investigates the cracking behavior of brittle heterogeneous materials. Unconfined, uniaxial compression tests are conducted on prismatic gypsum specimens containing either one, or two, inclusions. ...

  12. Stochastic versus Robust Optimization for a Transportation Problem

    E-Print Network [OSTI]

    Francesca Maggioni

    2015-03-05T23:59:59.000Z

    Mar 5, 2015 ... Abstract: In this paper we consider a transportation problem under uncertainty related to gypsum replenishment for a cement producer.

  13. Hyperspectral Mineral Mapping For Geothermal Exploration On The...

    Open Energy Info (EERE)

    reflectance spectra for alunite, kaolinitehalloysite, illite, gypsum, vegetation, and carbonate. A portable spectrometer is being used for in situ validation, along with...

  14. advisory board public: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    use of gypsum products in manure management systems. NRCS has developed a brochure and new signs1 Nutrient Management Advisory Board Approved Minutes of the April 18, 2013...

  15. Put only cleaned drug bottles into the same case as bottles of residential waste.

    E-Print Network [OSTI]

    Nakamura, Iku

    liquid (Including oil and aqueous materials) pH of aqueous materials should be>5. Unnecessary drugs, hazardous solids and sludge. Collected in November. Glass instruments, plaster, etc. Tightly compress

  16. PAINTING CHECKLIST GETTING STARTED

    E-Print Network [OSTI]

    Peters, Richard

    Sanding block o Sandpaper in a variety of grades o Scraper for loose surfaces and paint o Putty and fillers for gaps and holes · caulk for joints · plaster filler for walls · wood putty for timber · epoxy

  17. The Journal of John Waldie Theatre Commentaries, 1799-1830: no. 26 [Journal 37] December 9, 1816-February 16, 1817. Part 3

    E-Print Network [OSTI]

    Burwick, Frederick

    2008-01-01T23:59:59.000Z

    was in the service of Napoleon at Waterloo, a very elegantbut only in plaster, of Napoleon: the original is gone towhich was placed by Napoleon in the rooms fitted up for him

  18. CURRICULUM VITAE Paul Thomas Schoenemann

    E-Print Network [OSTI]

    Scheiber, Laura L.

    Bybee, Morten H. Christiansen, William Croft, Nick C. Ellis, John Holland, Jinyun Ke, Diane Larsen, and Jason Lewis, 2007, "Validation of Plaster Endocast Morphology Through 3D CT Image Analysis" American

  19. THE CITY UNIVERSITY OF NEW YORK Classified Civil Service Position Description

    E-Print Network [OSTI]

    Rosen, Jay

    . - Applies plasters to surfaces. - Takes proper care of all materials, tools and equipment. - Keeps records as required. - May operate a motor vehicle in the performance as assigned duties. Qualification Requirements 1

  20. Condensation mechanisms of an arsenic-rich vapor on GaAs (001) surfaces D. A. Murdick* and H. N. G. Wadley

    E-Print Network [OSTI]

    Wadley, Haydn

    . Wadley School of Engineering and Applied Science, University of Virginia, Charlottesville, Virginia 22904 of the incoming dimer. DOI: 10.1103/PhysRevB.75.125318 PACS number s : 81.05.Ea, 81.15.Aa, 68.43.Mn, 68.43.Pq I

  1. Growth, microstructure, and luminescent properties of direct-bandgap InAlP on relaxed InGaAs on GaAs substrates

    E-Print Network [OSTI]

    Beaton, D. A.

    Direct-bandgap InAlP alloy has the potential to be an active material in nitride-free yellow-green and amber optoelectronics with applications in solid-state lighting, display devices, and multi-junction solar cells. We ...

  2. Growth of alternating (1OO)/(lll )-oriented II-VI regions for quasi-phase-matched nonlinear optical devices on GaAs substrates

    E-Print Network [OSTI]

    Fejer, Martin M.

    ferroelectrics such as lithium nio- bate and potassium titanyl phosphate. Efficient operation is possible) nonlinear interactions. II-VI semiconductors, with transparency from the far in- frared to the visible phasematched interactions.' A powerful alternative technique, QPM, re- quires periodic patterning of the sign

  3. High-speed digital modulation of ultralow threshold (<1 mA) GaAs single quantum well lasers without bias

    SciTech Connect (OSTI)

    Lau, K.Y.; Bar-Chaim, N.; Derry, P.L.; Yariv, A.

    1987-07-13T23:59:59.000Z

    GaAlAs buried heterostructure lasers with submilliampere threshold current fabricated from single quantum well wafers can be driven directly with logic level signals without any current bias. The switch-on delay was measured to be <50 ps and no relaxation oscillation ringing was observed. These lasers permit fully o-smcapsn-smcapsreverse arrow-smcapso-smcapsf-smcapsf-smcaps multigigabit digital switching while at the same time obviating the need for bias monitoring and feedback control.

  4. Characterization of photochemically unpinned GaAs c. W. Wilmsen,a) P. D. Kirchner, J. M. Baker, D. T. McInturff, G. D. Pettit,

    E-Print Network [OSTI]

    Woodall, Jerry M.

    water was not applied to the substrate. The degree ofunpinning produced by this process has been found in deionized (DI) water. Some samples then received a final chemical treatment as The roomAs ( 100) surface has recently been reported by both photowashing and by Na2S'9H20 treatments. Both

  5. PHYSICAL REVIEW B 84, 245306 (2011) Formation process and superparamagnetic properties of (Mn,Ga)As nanocrystals in GaAs

    E-Print Network [OSTI]

    Dunin-Borkowski, Rafal E.

    2011-01-01T23:59:59.000Z

    de- vices by using dilute magnetic semiconductors (DMSs) are facing difficulties due to the lack a transition metal (TM) compound (to form a condensed magnetic semiconductor) or a TM.2,3 Interest- ingly

  6. PHYSICAL REVIEW B 88, 205203 (2013) Magnetic anisotropy of single Mn acceptors in GaAs in an external magnetic field

    E-Print Network [OSTI]

    Flatte, Michael E.

    2013-01-01T23:59:59.000Z

    .1103/PhysRevB.88.205203 PACS number(s): 75.50.Pp I. INTRODUCTION Magnetic semiconductors have attracted properties in spintronic devices. The most commonly investigated material as a magnetic semiconductor is Ga

  7. Atomic Layer Deposition of HfO2 Thin Films on Si and GaAs Substrates Justin C Hackley1

    E-Print Network [OSTI]

    Gougousi, Theodosia

    that have shown efficient growth of HfO2 films on Si-H at 100°C using amide precursors and heavy water.4 Hf and Materials Research Directorate, Army Research Laboratory, Aberdeen Proving Ground, MD, 21005-5069 ABSTRACT dielectrics in Metal Oxide Semiconductor Field Effect Transistors (MOSFET).5 However, one of the major issues

  8. Z .Thin Solid Films 313 314 1998 574 578 Linear and non-linear spectroscopy of GaAs and GaP

    E-Print Network [OSTI]

    Sipe,J. E.

    , together with the empirical tight-binding ETB Z .method. Specifically, we have calculated the dielectric conclusions about the applicability of the ETB method for the calculation of bulk optical responses have been . For such objects containing many .atoms the ETB method is usually used. Reasonably good agreement between theory

  9. 56 IEEE JOURNAL OF PHOTOVOLTAICS, VOL. 2, NO. 1, JANUARY 2012 Metamorphic GaAsP and InGaP Solar Cells on GaAs

    E-Print Network [OSTI]

    Haller, Gary L.

    56 IEEE JOURNAL OF PHOTOVOLTAICS, VOL. 2, NO. 1, JANUARY 2012 Metamorphic GaAsP and InGaP Solar bandgap range. Index Terms--Epitaxy, GaAsP, InGaP, metamorphic. I. INTRODUCTION TODAY'S highest efficiency

  10. GaAs, AlGaAs and InGaP Tunnel Junctions for Multi-Junction Solar Cells Under Concentration: Resistance Study

    SciTech Connect (OSTI)

    Wheeldon, Jeffrey F.; Valdivia, Christopher E.; Walker, Alex; Kolhatkar, Gitanja; Hall, Trevor J.; Hinzer, Karin [Centre for Research in Photonics, University of Ottawa, Ottawa, ON (Canada); Masson, Denis; Riel, Bruno; Fafard, Simon [Cyrium Technologies Inc., Ottawa, ON (Canada); Jaouad, Abdelatif; Turala, Artur; Ares, Richard; Aimez, Vincent [Centre de Recherche en Nanofabrication et en Nanocaracterisation CRN2, Universite de Sherbrooke, Sherbrooke, QC (Canada)

    2010-10-14T23:59:59.000Z

    The following four TJ designs, AlGaAs/AlGaAs, GaAs/GaAs, AlGaAs/InGaP and AlGaAs/GaAs are studied to determine minimum doping concentration to achieve a resistance of <10{sup -4} {omega}{center_dot}cm{sup 2} and a peak tunneling current suitable for MJ solar cells up to 1500-suns concentration (operating current of 21 A/cm{sup 2}). Experimentally calibrated numerical models are used to determine how the resistance changes as a function of doping concentration. The AlGaAs/GaAs TJ design is determined to require the least doping concentration to achieve the specified resistance and peak tunneling current, followed by the GaAs/GaAs, and AlGaAs/AlGaAs TJ designs. The AlGaAs/InGaP TJ design can only achieve resistances >5x10{sup -4} {omega}cm{sup 2}.

  11. Elastomeric Nanoparticle Composites Covalently Bound to Al2O3/GaAs Hyon Min Song, Peide D. Ye,, and Albena Ivanisevic*,,|

    E-Print Network [OSTI]

    Ye, Peide "Peter"

    . The mechanical properties of the surface-bound nanocomposites were tested using nanoindentation experiments include block copolymer-functionalized silicate,17 GaAs-PMMA (poly- (methyl methacrylate)) hybrids,18

  12. Possibilities of Sulphur as a Soil Amendment.

    E-Print Network [OSTI]

    Fraps, G. S. (George Stronach)

    1930-01-01T23:59:59.000Z

    and being sometimes mistaken for gold, ,are called "fool's gold." The pyrite deposits in Texas are usually too small to be of commercial value. Gypsum. Gypsum (82, 83) is a hydrous calcium sulphate, occurring abundantly in many parts of Texas in various... subsoil ............................. Acadia clay loam ............................... Acadia clay loam subsoil ....................... Acadia clay loam subsoil ....................... Orangeburg fine sandy loam .................... Orangeburg fine...

  13. Dept. of Soil A.J. Bussan

    E-Print Network [OSTI]

    Balser, Teri C.

    remember, gypsum will not change pH! TOMATO #12;LIMING MATERIALS Dolomitic = CaCO3·MgCO3 Calcitic = CaCO3 Fly ash = CaO, Ca(OH2), CaCO3 Gypsum = CaSO4 CaCO3 + 2H+ = Ca2+ + CO2 + H2O The carbonate affects

  14. Low DC-power Ku-band RTD VCO based on an InP monolithic RTD/HBT technology

    E-Print Network [OSTI]

    Yang, Kyounghoon

    device technologies such as InGaP/GaAs HBT [1], GaAs HFET [2], GaAs pHEMT [3], and Si CMOS [4]. Along

  15. VOLUME 76, NUMBER 8 P H Y S I C A L R E V I E W L E T T E R S 19 FEBRUARY 1996 Spin Splitting of Single 0D Impurity States in Semiconductor Heterostructure Quantum Wells

    E-Print Network [OSTI]

    Reed, Mark

    cm23 Si doped GaAs contact, a 15 nm undoped GaAs spacer layer, a 8.5 nm undoped Al0.27Ga0.73As bottom GaAs spacer layer, and a 1.8 3 1018 cm23 Si doped GaAs top contact. Square mesas with lateral dimensions from 2 to 64 mm are fabricated using standard photolithography techniques. Two terminal I V

  16. Monolithically Peltier-cooled vertical-cavity surface-emitting lasers Paul FL Berger, Niloy K. Dutta, Kent D. Choquette, Ghulam Hasnain, and Naresh Chand

    E-Print Network [OSTI]

    Monolithically Peltier-cooled vertical-cavity surface-emitting lasers Paul FL Berger, Niloy K. The thermoelectric element is the n + -GaAs substrate based on the Peltier effect. A variation of active region contact on the n + -GaAs substrate. The thermoelectric (Peltier) ef- fect of the n f -GaAs substrate can

  17. Elden Tefft: An Informal Look at a Founding Father of Twentieth Century Bronze Casting in the United States

    E-Print Network [OSTI]

    Voorhees, Craig

    2011-07-29T23:59:59.000Z

    melts and runs out down a hole left in the bottom of the mold. This leaves a hollow in the dried plaster in exactly the same shape left by the wax model. The hole in the bottom of the mold is then plugged up and melted bronze is poured into the mold... and the bronze solidifies in the hollow left behind in the plaster when the wax melted and ran out. The lost wax process gets its name because the wax disappears when the mold is heated. Using the lost wax casting technique, large and complex sculptures can...

  18. Bruce L. Cutright Bureau of Economic Geology

    E-Print Network [OSTI]

    Yang, Zong-Liang

    and chlorinated organic compounds from settling ponds through multiple aquifer systems and fate and transport of radioactive elements from phosphate mining gypsum waste stacks. He also served, water reuse projects, wastewater recycling through wetlands, and international projects in Central

  19. Stable isotope geochemistry of sulfur bearing minerals and clay mineralogy of some soils and sediments in Loot Desert, central Iran

    E-Print Network [OSTI]

    Ahmad, Sajjad

    Stable isotope geochemistry of sulfur bearing minerals and clay mineralogy of some soils Keywords: Sulfur geochemistry Gypsum crystallization water Clay mineralogy Palygorskite Iranian soils Loot technique and clay mineralogy were studied in different landforms in Loot Desert, central Iran. Four

  20. Journal of California and Great Basin Anthropology | Vol. 32, No. 1 (2012) | pp. 4764 Chemical Composition, Mineralogy,

    E-Print Network [OSTI]

    2012-01-01T23:59:59.000Z

    Composition, Mineralogy, and Physical Structure of Pigments on Arrow and Dart Fragments from Gypsum Cave), and electron microprobe (EM) to determine their chemical composition, mineralogy, and physical structure pigments. Although variation in composition and mineralogy suggests some degree of experimentation

  1. Environmental chamber measurements of mercury flux from coal utilization by-products

    SciTech Connect (OSTI)

    Pekney, N.J.; Martello, D.V.; Schroeder, K.T.; Granite, E.J.

    2009-05-01T23:59:59.000Z

    An environmental chamber was constructed to measure the mercury flux from coal utilization by-product (CUB) samples. Samples of fly ash, FGD gypsum, and wallboard made from FGD gypsum were tested under both dark and illuminated conditions with or without the addition of water to the sample. Mercury releases varied widely, with 7-day experiment averages ranging from -6.8 to 73 ng/m2 h for the fly ash samples and -5.2 to 335 ng/m2 h for the FGD/wallboard samples. Initial mercury content, fly ash type, and light exposure had no observable consistent effects on the mercury flux. For the fly ash samples, the effect of a mercury control technology was to decrease the emission. For three of the four pairs of FGD gypsum and wallboard samples, the wallboard sample released less (or absorbed more) mercury than the gypsum.

  2. 2005 EPA WIPP RECERTIFICATION FACT SHEET No. 6 Karst in the Area of WIPP

    E-Print Network [OSTI]

    on wells drilled into the Culebra Dolomite within the Land Withdrawal Boundary show evidence of flow, such as halite (salt) and gypsum. tory through the subsurface. may form when rainwater, reacting with carbon

  3. Continuing Education and Training Needs of the Southern Forest Industry.

    E-Print Network [OSTI]

    Thomas, John K.; Albrecht, Don E.; Lee, J. Charles; Klinoff, Roger

    1985-01-01T23:59:59.000Z

    and Paper Champion International Kirby Forest Industries Louisiana -Pacific Owens Illinois Temple EasTex Bear Island Paper Chesapeake Owens Illinois Union Camp United States Gypsum V irginia Fibr~ Westvaco CSX Resources Westvaco 13 14...

  4. This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research

    E-Print Network [OSTI]

    Paytan, Adina

    of Geology and Environmental Geosciences, Northern Illinois University, Davis Hall 312, DeKalb, IL 60115, USA Chetumal, Quintana Roo to Campeche, Campeche. The presence of gypsum quarries in the area is also

  5. Alternate stabilizers: solution towards reducing sulfate swell in expansive clay subgrades in Dallas district 

    E-Print Network [OSTI]

    Rajendran, Deepa

    1997-01-01T23:59:59.000Z

    The practice of using lime as a stabilizer during construction of pavements is widespread and is considered economical. However under certain conditions, the beneficial effects of lime stabilization is overridden. Proximity of gypsum deposits...

  6. Building Stones

    E-Print Network [OSTI]

    2012-01-01T23:59:59.000Z

    anhydrite and gypsum near Wadi el-Anba’ut, Red Sea coast,West Bank (ED:3; small) Wadi Rayan Formation of the MokattamNK & Pt-R? ; medium) 21. in Wadi Sheikh Yasin east of Zawyet

  7. Investigation of a mercury speciation technique for flue gas desulfurization materials

    SciTech Connect (OSTI)

    Lee, J.Y.; Cho K.; Cheng L.; Keener, T.C.; Jegadeesan G.; Al-Abed, S.R. [University of Cincinnati, Cincinnati, OH (United States). Department of Chemical and Materials Engineering

    2009-08-15T23:59:59.000Z

    Most of the synthetic gypsum generated from wet flue gas desulfurization (FGD) scrubbers is currently being used for wallboard production. Because oxidized mercury is readily captured by the wet FGD scrubber, and coal-fired power plants equipped with wet scrubbers desire to benefit from the partial mercury control that these systems provide, some mercury is likely to be bound in with the FGD gypsum and wallboard. In this study, the feasibility of identifying mercury species in the FGD gypsum and wallboard samples was investigated using a large sample size thermal desorption method and samples from power plants in Pennsylvania. Potential candidates of pure mercury standards including mercuric chloride, mercurous chloride, mercury oxide, mercury sulfide, and mercuric sulfate were analyzed to compare their results with those obtained from FGD gypsum and dry wallboard samples. Although any of the thermal evolutionary curves obtained from these pure mercury standards did not exactly match with those of the FGD gypsum and wallboard samples, it was identified that Hg{sub 2}Cl{sub 2} and HgCl{sub 2} could be candidates. An additional chlorine analysis from the gypsum and wallboard samples indicated that the chlorine concentrations were approximately 2 orders of magnitude higher than the mercury concentrations, suggesting possible chlorine association with mercury. 21 refs., 5 figs., 3 tabs.

  8. Luminescence properties of light-emitting diodes based on GaAs with the up-conversion Y{sub 2}O{sub 2}S:Er,Yb luminophor

    SciTech Connect (OSTI)

    Gruzintsev, A. N. [Russian Academy of Sciences, Institute of Problems of Microelectronics Technology (Russian Federation)], E-mail: gran@ipmt-hpm.ac.ru; Barthou, C.; Benalloul, P. [Institute des NanoSciences (France)

    2008-03-15T23:59:59.000Z

    Y{sub 2}O{sub 2}S luminophors doped with Er{sup 3+} and Yb{sup 3+} ions are produced by means of solid-phase synthesis and deposited onto standard AL123A infrared light-emitting diodes. When excited with 940 nm radiation from a light-emitting diode, the structures exhibit intense visible up-conversion luminescence. A maximal brightness of 2340 cd/m{sup 2} of green and red up-conversion luminescence at corresponding wavelengths around 550 and 600 nm is observed for the Y{sub 2}O{sub 2}S compound doped with 2 at % Er{sup 3+} ions and 6 at % Yb{sup 3+} ions. The ratio of the intensity of green (or red) up-conversion luminescence to the intensity of infrared Stokes luminescence increases with increasing applied voltage. The efficiency of visible emission of the light-emitting diode structures is {eta} = 1.2 lm/W at an applied voltage of 1.5 V.

  9. GaAs multiple-quantum-well reflector modulators with 4:l contrast ratios A. Salvador, K. Adorni,@K. Kishino,b) M. S. l%U, and H. Morkoq.

    E-Print Network [OSTI]

    ,,, G%,,As (3 X 1018cmv3 be- `) On leave from Shin-Etsu Handotai Co., Ltd., Gunma, Japan. "On leave from

  10. GaAs Nanowire Array Solar Cells with Axial p-i-n Junctions Maoqing Yao, Ningfeng Huang, Sen Cong, Chun-Yung Chi, M. Ashkan Seyedi, Yen-Ting Lin, Yu Cao,

    E-Print Network [OSTI]

    Zhou, Chongwu

    for future low-cost, high-efficiency photovoltaics. KEYWORDS: Nanowires, solar cells, gallium arsenide, axial.58% efficiency. Simulations show that axial junctions are more tolerant to doping variation than radial junctions and shallow junctions are essential for a high extraction efficiency. Our approach opens up great opportunity

  11. High performance 70 nm In0.8GaP/In0.4AlAs/In0.35GaAs Metamorphic HEMT With Pd Schottky Contacts

    E-Print Network [OSTI]

    Seo, Kwang Seok

    contacts, due to low diffusivity with InGaP of Pd as well as its high SBH [9], the distance between Schottky contact due to its low diffusion of Pd to InGaP. The fabricated 70 nm MHEMT's with Pd Schottky

  12. Imagination Made Tangible Aspiring designers at NJSOA are no longer limited to two

    E-Print Network [OSTI]

    Bieber, Michael

    and heavy paper, 3D printers that build objects from layers of plaster, and a CNC Router that can mill of their digital work. Above, Garber displays a detailed model made with the 3D printer. the challenge: Establish the FABLAB's laser cutter, CNC Router and 3D printer to build a model of Atlantic City circa 1952

  13. Cement and Concrete Research, 2005, 35(11), 2081-2086, doi:10.1016/j.cemconres.2004.05.052 TTThhheee iiinnnfffllluuueeennnccceee ooofff wwwooooooddd aaaqqquuueeeooouuusss eeexxxtttrrraaaccctttiiivvveeesss ooonnn ttthhheee hhhyyydddrrraaatttiiiooonnn

    E-Print Network [OSTI]

    Boyer, Edmond

    Cement and Concrete Research, 2005, 35(11), 2081-2086, doi:10.1016/j.cemconres.2004.05.052 1 of mineral binders (cement, concrete or plaster) has been a matter of major concern for several decades (called `extractives') which could delay the setting of cement [11], [12], [13] and [14]. In some other

  14. ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton GIT 2009

    E-Print Network [OSTI]

    Colton, Jonathan S.

    ­ Air (oxygen), vacuum, inert gas (argon) · Heating ­ External - electric, gas, oil ­ Internal Prof. J.S. Colton © GIT 2009 11 Processes · Sand · Shell · Plaster · Ceramic · Investment · Lost foam Metals processed by casting · Sand casting ­ 60% · Investment casting ­ 7% · Die casting ­ 9% · Permanent

  15. Community Geothermal Technology Program: Silica bronze project. Final report

    SciTech Connect (OSTI)

    Bianchini, H.

    1989-10-01T23:59:59.000Z

    Objective was to incorporate waste silica from the HGP-A geothermal well in Pohoiki with other refractory materials for investment casting of bronze sculpture. The best composition for casting is about 50% silica, 25% red cinders, and 25% brick dust; remaining ingredient is a binder, such as plaster and water.

  16. ASPIRING DESIGNERS ARE NO LONGER LIMITED to two-dimensional expressions of their ideas on

    E-Print Network [OSTI]

    Bieber, Michael

    for acrylic and heavy paper, 3-D printers that build objects from layers of plaster, and a CNC router that can, the FABLAB provides a range of hardware that is computer numerically controlled (CNC) -- laser cutters, the machines translate students' concepts into three- dimensional prototypes or models. "Our CNC tools have

  17. Remembrance of an absence Report by Cati Vaucelle

    E-Print Network [OSTI]

    Ishii, Hiroshi

    travail. I chose to dismember a Barbie doll that I created out of wax. The Barbie being for a while a representation of the woman for a child. I chose the white wax, the wax being a way a woman suffers regularly & the plaster sculpted with chisel, and the angelic face of the doll made of white wax. This sculpture is a tool

  18. MIXING AND CHAOTIC MICROSTRUCTURE \\Lambda Yuefan Deng and James Glimm y

    E-Print Network [OSTI]

    New York at Stoney Brook, State University of

    will fall. However, it is not through lack of support from the air that the water falls. The pressure the ceiling of a room plastered uniformly with water to a depth of 1 meter (Figure 1). The layer of water of the atmosphere is equivalent to that of a layer of water 10 meters thick, quite suffic

  19. 2000. The Journal of Arachnology 28:243244 RESEARCH NOTE

    E-Print Network [OSTI]

    Carrel, James E.

    . Each cage contained four vertical glass rods (20 cm 4 mm o.d.) arranged in a square 5 cm on a side of a transparent bottle, embedding the rods in a 2 cm thick layer of patching plaster poured into the bot- tom sealed in this manner, the in- expensive bottle cage proved to be mold-free and almost airtight. Two days

  20. Hillside C-type Renovation Issues and Remedies

    E-Print Network [OSTI]

    California at Berkeley, University of

    concrete and masonry Overhang Outside Inside Tiles Outer Alu frame Drill drain holes here throughout length Exterior wall bricks concrete and masonry Stone slab does not cover sill width Drain channel Outer Alu with new Marbonite ­ Concealing pipes Stone up to guiderail Porous cracked plaster outside #12;To Deputy

  1. Evaluating biological control of fire ants using phorid flies: effects on competitive interactions

    E-Print Network [OSTI]

    Mottern, Jason Lewis

    2002-01-01T23:59:59.000Z

    500 P. 15 tricuspis pupae were shipped weekly until the completion of the experiments. Pupae arrived in 59. 2-ml plastic souffles cups (Solo Cup Company, Urbana, IL) filled with white plaster to retain moisture. As the shipments arrived, pupae were...

  2. JOURNAL DE PHYSIQUE Colloque C5, supplment au n12, Tome 43, dcembre 1982 page C5-303

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    . In 1975, Seki (1) using TEG instead of TMG obtained high mobility GaAs. His GaAs was almost fmeof C. He of TEG sources. He got high mobility samples ^ 105 cni2/V.§ec in GaAs grown from TEG. PL spectra did from the thermal decbm- p6fftio.n o f TE!G, i s t o some extend 'incorporate$ i n the growing Ga

  3. Characterization of Thallium Bromide (TlBr) for Room Temperature Radiation Detectors

    E-Print Network [OSTI]

    Smith, Holland McTyeire

    2013-01-01T23:59:59.000Z

    efficiency in GaAs radiation detectors,” Nuclear Instrumentscrystals used for radiation detectors,” Nuclear Instrumentscrystals used as radiation detectors,” Nuclear Science, IEEE

  4. THSE DE DOCTORAT Spcialit Physique

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    -thin GaAs and CIGS solar cells soutenue le 18 Décembre 2013 Composition du jury : M. PELOUARD Jean-Luc LPN

  5. Transcending QCD in Nanostructured Solar Cells G. Galli S. Kauzlarich

    E-Print Network [OSTI]

    achieved! - But: fracking of natural gas moved grid parity to 0.3$/W 2. Science/Technology: - GaAs: 29% lab

  6. Infrared emission from the substrate of GaAs-based semiconductor lasers Mathias Ziegler,1,a

    E-Print Network [OSTI]

    Peinke, Joachim

    by metal- organic vapor phase epitaxy on a n-type GaAs substrate. The red-emitting laser employs an InGaP

  7. Atomic layer deposition of GaN using GaCl3 and NH3 Oh Hyun Kim, Dojun Kim, and Tim Andersona

    E-Print Network [OSTI]

    Anderson, Timothy J.

    be grown at lower temperature than by CVD. As example, ALD growth of device quality GaAs, GaP, and InGaP

  8. Necessity of Ga prelayers in GaAs/Ge growth using gas-source molecular beam epitaxy

    E-Print Network [OSTI]

    in a highly defective GaAs layer.as5 Recently, InGaP light-emitting diodes have been fabricated on Si using

  9. Simulation and Experiment of Wide Bandgap Material Based Nonvolatile Memory

    E-Print Network [OSTI]

    LI, ZONGLIN

    2012-01-01T23:59:59.000Z

    than SiC, GaN, GaAs, sapphire substrate; (3) The size ofA. Dadgar, “GaN-based opoelectronics on silicon substrates”,

  10. Innovative Clean Coal Technology (ICCT): Demonstration of innovative applications of technology for cost reductions to the CT-121 FGD process. Quarterly report No. 6, July--September 1991

    SciTech Connect (OSTI)

    Not Available

    1991-11-15T23:59:59.000Z

    The project`s objective is to demonstrate innovative applications of technology for cost reduction for the Chiyoda Thoroughbred-121 (CT-121) process. The CT-121 process is a wet FGD process that removes SO{sub 2}, can achieve simultaneous particulate control, and can produce a salable by-product gypsum thereby reducing or even eliminating solid waste disposal problems. Figure 1 shows a flow schematic of the process. CT-121 removes SO{sub 2} and particulate matter in a unique limestone-based scrubber called the Jet Bubbling Reactor (JBR). IN the JBR, flue gas bubbles beneath the slurry, SO{sub 2} is absorbed, and particulate matter is removed from the gas. The agitator circulates limestone slurry to ensure that fresh reactant is always available in the bubbling or froth zone sot that SO{sub 2} removal can proceed at a rapid rate. Air is introduced into the bottom of the JBR to oxidize the absorbed SO{sub 2} to sulfate, and limestone is added continuously to neutralize the acid slurry and form gypsum. The JBR is designed to allow ample time for complete oxidation of the SO{sub 2}, for complete reaction of the limestone, and for growth of large gypsum crystals. The gypsum slurry is continuously withdrawn from the JBR and is to be dewatered in a gypsum stack. The stacking technique involves filing a diked area with gypsum slurry, allowing the gypsum solids to settle, and removing clear liquid from the top of the stack for recycle back to the process.

  11. INSTITUTE OF PHYSICS PUBLISHING SEMICONDUCTOR SCIENCE AND TECHNOLOGY Semicond. Sci. Technol. 22 (2007) 2934 doi:10.1088/0268-1242/22/2/006

    E-Print Network [OSTI]

    2007-01-01T23:59:59.000Z

    INSTITUTE OF PHYSICS PUBLISHING SEMICONDUCTOR SCIENCE AND TECHNOLOGY Semicond. Sci. Technol. 22 mismatch between Si and direct bandgap III­V compound semiconductors such as GaAs makes the direct growth of compositionally graded Si1-xGex buffer layers to bridge the gap between Si and GaAs lattice constants (i

  12. 1204 IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 34, NO. 9, SEPTEMBER 1999 Breakdown in Millimeter-Wave Power InP

    E-Print Network [OSTI]

    del Alamo, Jesús A.

    1204 IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 34, NO. 9, SEPTEMBER 1999 Breakdown in Millimeter-Wave Power InP HEMT's: A Comparison with GaAs PHEMT's J. A. del Alamo and M. H. Somerville Abstract's) deliver lower output power than GaAs pseudomorphic HEMT's (PHEMT's) throughout most of the millimeter

  13. Sparse gallium arsenide to silicon metal waferbonding for heterogeneous monolithic microwave integrated circuits

    E-Print Network [OSTI]

    Bickford, Justin Robert

    2008-01-01T23:59:59.000Z

    lasers utilizing an InGaP etch-stop layer,” Semiconductor1992). Cirtic acid GaAs from InGaP: D. Arslan, A. Dehé, and1999). Hydrochloric acid InGaP from GaAs: J. R. Lothian, J.

  14. Shot noise in self-assembled InAs quantum dots A. Nauen,1,

    E-Print Network [OSTI]

    Hohls, Frank

    they pro- vide zero-dimensional states of microscopic dimensions. Furthermore, it is possible to select structure of 40 40 m2 area. A 15 nm undoped GaAs spacer layer and a GaAs buffer with graded doping on both

  15. Passively modelocked 832 nm vertical-external-cavity surface-emitting

    E-Print Network [OSTI]

    Keller, Ursula

    , focused into an optical spot with dimensions of 100 Ã? 200 mm. The SESAM consisted of an AlAs/Al0.2Ga0.8As DBR, a spacer layer of GaAs0.75P0.25, a 4.8 nm GaAs quantum well and a 2 nm-thick capping layer of Ga

  16. Method of making suspended thin-film semiconductor piezoelectric devices

    DOE Patents [OSTI]

    Casalnuovo, Stephen A. (Albuquerque, NM); Frye-Mason, Gregory C. (Cedar Crest, NM)

    2001-01-01T23:59:59.000Z

    A process for forming a very thin suspended layer of piezoelectric material of thickness less than 10 microns. The device is made from a combination of GaAs and AlGaAs layers to form either a sensor or an electronic filter. Onto a GaAs substrate is epitaxially deposited a thin (1-5 micron) sacrificial AlGaAs layer, followed by a thin GaAs top layer. In one embodiment the substrate is selectively etched away from below until the AlGaAs layer is reached. Then a second selective etch removes the sacrificial AlGaAs layer, that has acted here as an etch stop, leaving the thin suspended layer of piezoelectric GaAs. In another embodiment, a pattern of small openings is etched through the thin layer of GaAs on top of the device to expose the sacrificial AlGaAs layer. A second selective etch is done through these openings to remove the sacrificial AlGaAs layer, leaving the top GaAs layer suspended over the GaAs substrate. A novel etchant solution containing a surface tension reducing agent is utilized to remove the AlGaAs while preventing buildup of gas bubbles that would otherwise break the thin GaAs layer.

  17. Nanoheteroepitaxy of gallium arsenide on strain-compliant silicon-germanium nanowires

    SciTech Connect (OSTI)

    Chin, Hock-Chun; Gong, Xiao; Yeo, Yee-Chia [Department of Electrical and Computer Engineering, National University of Singapore (NUS), Singapore 117576 (Singapore); Ng, Tien Khee; Loke, Wan Khai; Wicaksono, Satrio; Yoon, Soon Fatt [School of Electrical and Electronic Engineering, Nanyang Technological University (NTU), Nanyang Avenue, Singapore 639798 (Singapore); Wong, Choun Pei; Shen, Zexiang [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University (NTU), Singapore 637371 (Singapore)

    2010-07-15T23:59:59.000Z

    Heterogeneous integration of high-quality GaAs on Si-based substrates using a selective migration-enhanced epitaxy (MEE) of GaAs on strain-compliant SiGe nanowires was demonstrated for the first time. The physics of compliance in nanoscale heterostructures was captured and studied using finite-element simulation. It is shown that nanostructures can provide additional substrate compliance for strain relief and therefore contribute to the formation of defect-free GaAs on SiGe. Extensive characterization using scanning electron microscopy and cross-sectional transmission electron microscopy was performed to illustrate the successful growth of GaAs on SiGe nanowire. Raman and Auger electron spectroscopy measurements further confirmed the quality of the GaAs grown and the high growth selectivity of the MEE process.

  18. Low-cost, high-efficiency solar cells utilizing GaAs-on-Si technology. Annual subcontract report, 1 August 1991--31 July 1992

    SciTech Connect (OSTI)

    Vernon, S.M. [Spire Corp., Bedford, MA (United States)

    1993-04-01T23:59:59.000Z

    This report describes work to develop technology to deposit GaAs on Si using a nucleation layer of atomic-layer-epitaxy-grown GaAs or AlAs on Si. This ensures two-dimensional nucleation and should lead to fewer defects in the final GaAs layer. As an alternative, we also developed technology for depositing GaAs on sawtooth-patterned Si. Preliminary studies showed that this material can have a very low defect density, {approximately} 1 {times} 10{sup 5} cm{sup {minus}5}, as opposed to our conventionally grown GaAs on SL which has a typical defect density of over 1 {times}10{sup 7} cm{sup {minus}2}. Using these two now methods of GaAs-on-Si material growth, we made solar cells that are expected to show higher efficiencies than those of previous cells.

  19. Low-cost, high-efficiency solar cells utilizing GaAs-on-Si technology

    SciTech Connect (OSTI)

    Vernon, S.M. (Spire Corp., Bedford, MA (United States))

    1993-04-01T23:59:59.000Z

    This report describes work to develop technology to deposit GaAs on Si using a nucleation layer of atomic-layer-epitaxy-grown GaAs or AlAs on Si. This ensures two-dimensional nucleation and should lead to fewer defects in the final GaAs layer. As an alternative, we also developed technology for depositing GaAs on sawtooth-patterned Si. Preliminary studies showed that this material can have a very low defect density, [approximately] 1 [times] 10[sup 5] cm[sup [minus]5], as opposed to our conventionally grown GaAs on SL which has a typical defect density of over 1 [times]10[sup 7] cm[sup [minus]2]. Using these two now methods of GaAs-on-Si material growth, we made solar cells that are expected to show higher efficiencies than those of previous cells.

  20. Scanning probe microscopy: Sulfate minerals in scales and cements

    SciTech Connect (OSTI)

    Hall, C. [Schlumberger Cambridge Research (United Kingdom)

    1995-11-01T23:59:59.000Z

    The principles of scanning probe microscopy (SPM) are illustrated with examples from oilfield mineralogy, particularly emphasizing sulfate minerals involved in scale formation and cement hydration chemistry. The topography of the (010) cleavage surface of gypsum observed by atomic force microscopy shows atomically flat terraces separated by shallow steps often only one unit cell high. SPM allows direct observation of processes on mineral surfaces while they are in contact with solutions. The dissolution etching and crystal growth of gypsum and barite are discussed and rates of step migration estimated. The orientation of steps is related to the crystallographic axes. The action of phosphonate crystal growth inhibitor on gypsum and of a chelating scale solvent on barite are also shown. The multiphase microstructure of an oilwell cement clinker is described in relation to its hydration chemistry in contact with water and its reaction with sulfate ions.

  1. Macroscopic corrosion front computations of sulfate attack in sewer pipes based on a micro-macro reaction-diffusion model

    E-Print Network [OSTI]

    Chalupecký, Vladimír; Kruschwitz, Jens; Muntean, Adrian

    2012-01-01T23:59:59.000Z

    We consider a two-scale reaction diffusion system able to capture the corrosion of concrete with sulfates. Our aim here is to define and compute two macroscopic corrosion indicators: typical pH drop and gypsum profiles. Mathematically, the system is coupled, endowed with micro-macro transmission conditions, and posed on two different spatially-separated scales: one microscopic (pore scale) and one macroscopic (sewer pipe scale). We use a logarithmic expression to compute values of pH from the volume averaged concentration of sulfuric acid which is obtained by resolving numerically the two-scale system (microscopic equations with direct feedback with the macroscopic diffusion of one of the reactants). Furthermore, we also evaluate the content of the main sulfatation reaction (corrosion) product---the gypsum---and point out numerically a persistent kink in gypsum's concentration profile. Finally, we illustrate numerically the position of the free boundary separating corroded from not-yet-corroded regions.

  2. Advanced Flue Gas Desulfurization (AFGD) demonstration project: Volume 2, Project performance and economics. Final technical report

    SciTech Connect (OSTI)

    NONE

    1996-04-30T23:59:59.000Z

    The project objective is to demonstrate removal of 90--95% or more of the SO{sub 2} at approximately one-half the cost of conventional scrubbing technology; and to demonstrate significant reduction of space requirements. In this project, Pure Air has built a single SO{sub 2} absorber for a 528-MWe power plant. The absorber performs three functions in a single vessel: prequencher, absorber, and oxidation of sludge to gypsum. Additionally, the absorber is of a co- current design, in which the flue gas and scrubbing slurry move in the same direction and at a relatively high velocity compared to conventional scrubbers. These features all combine to yield a state- of-the-art SO{sub 2} absorber that is more compact and less expensive than conventional scrubbers. The project incorporated a number of technical features including the injection of pulverized limestone directly into the absorber, a device called an air rotary sparger located within the base of the absorber, and a novel wastewater evaporation system. The air rotary sparger combines the functions of agitation and air distribution into one piece of equipment to facilitate the oxidation of calcium sulfite to gypsum. Additionally, wastewater treatment is being demonstrated to minimize water disposal problems inherent in many high-chloride coals. Bituminous coals primarily from the Indiana, Illinois coal basin containing 2--4.5% sulfur were tested during the demonstration. The Advanced Flue Gas Desulfurization (AFGD) process has demonstrated removal of 95% or more of the SO{sub 2} while providing a commercial gypsum by-product in lieu of solid waste. A portion of the commercial gypsum is being agglomerated into a product known as PowerChip{reg_sign} gypsum which exhibits improved physical properties, easier flowability and more user friendly handling characteristics to enhance its transportation and marketability to gypsum end-users.

  3. The Composition of the Soils of the Texas Panhandle.

    E-Print Network [OSTI]

    Fraps, G. S.

    1915-01-01T23:59:59.000Z

    in the Panhandle area . Cottonwood Loam.-This soil is derived from gypsum and is of low productiveness on account of the gypsum content. Only one or two small areas were found. The surface soil is 8 to 12 inches deep and of a dark brown loam to silty loam... in this series is a black heavy clay, fm1nd in only small areas and not shown on the map of the area. R1:chji.eld 8eries.-:-The type of thiR series is a dark grayish black loam with no tinge of red in soil and ? sn bsoil. an 1 in this respect is quite...

  4. A field evaluation of the movement of selected metals in revegetated strip mine overburden and laboratory assessment of transport mechanisms 

    E-Print Network [OSTI]

    Launius, Kenneth Wayne

    1980-01-01T23:59:59.000Z

    placement of materials following the excavation and sampling of lignite at a test pit. The effect of varying ratios of lime and gypsum had on revegetation were studied. Resultant overburden'pH and electrical conductivity (EC) wire evaluated... and gypsum have on pH, electr 1cal conductiv1ty (EC) and bermudagrass yield, Lime requirement ( LR) was determ1ned on a sample of the overburden from the test pit. One, 2, 4, 8, j6 and 32 meq of reagent grade CaCO, were mixed wi th 1ndividual IOD g...

  5. Imperial Reservoir KOFA NATIONAL

    E-Print Network [OSTI]

    Laughlin, Robert B.

    247 79 79 7 115 62 72 78 79 86 115 163 18 72 74 78 115 18 62 95 371 95 94 247 Solar Energy Study Areas of 7/21/2009) Solar Energy Study Area (as of 6/5/2009) BLM Lands Being Analyzed for Solar Development Imperial Plaster City Live Oak Springs Seeley Coyote Wells El Centro Holtville Boulevard Campo Tecate Heber

  6. Carbon isotope fractionation in autotrophic Chromatium

    E-Print Network [OSTI]

    Wong, William Wai-Lun

    1974-01-01T23:59:59.000Z

    CARSON ISOTOPE FRACTIONATION IN AUTOTPOPHIC CHROYATIUN A Thesis 'JILLIAJJ J JAI LJJN BONG Submitted to the Graduate College of Texas A&H University in partial fulfillment of the requirenent for the degree of PLASTER OF SCIENCE August 1974...) August 1974 ABSTRACT Carbon Isotope Fractionation in Autotrophic Chromatium (August 1974) blilliam Wai-Lun Wang, B. S. , Texas Lutheran College Co-Chairmen of Advisory Committee: Dr. Isilliam N. Sackett Dr. Chauncey P. . Benedict Bacterial cells...

  7. DEDALOS NREL: Cooperative Research and Development Final Report, CRADA Number CRD-07-237

    SciTech Connect (OSTI)

    Friedman, D.

    2013-06-01T23:59:59.000Z

    Currently High Concentration Photovoltaic (HCPV) terrestrial modules are based on the combination of optic elements that concentrate the sunlight into much smaller GaAs space cells to produce electricity. GaAs cell technology has been well developed for space applications during the last two decades, but the use of GaAs cells under concentrated sunlight in terrestrial applications leaves unanswered questions about performance, durability and reliability. The work to be performed under this CRADA will set the basis for the design of high-performance, durable and reliable HCPV terrestrial modules that will bring down electricity production costs in the next five years.

  8. Cement and Concrete Research, 2010, 40(2), 242-252, doi:10.1016/j.cemconres.2009.10.008 SSSooommmeee aaassspppeeeccctttsss ooofff ccceeelllllluuulllooossseee eeettthhheeerrrsss iiinnnfffllluuueeennnccceee ooonnn wwwaaattteeerrr tttrrraaannnssspppooorrrttt

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    Cement and Concrete Research, 2010, 40(2), 242-252, doi:10.1016/j.cemconres.2009.10.008 1 of cement-based materials in both fresh and hardened state. Investigations of the porous network (mercury, factory-made mortars are mainly composed of mineral binders (cement, lime and/or gypsum), sands

  9. CEMENT RELATED RESEARCH HYDROGEOCHEMISTRY GROUP

    E-Print Network [OSTI]

    Politècnica de Catalunya, Universitat

    CEMENT RELATED RESEARCH HYDROGEOCHEMISTRY GROUP Josep M. Soler Jordi Cama Carles Ayora Ana Trapote.soler@idaea.csic.es #12;NOMECLATURE cement + water = hardened cement paste cement + water + sand = mortar cement + waterC) clinker + gypsum portland cement PORTLAND CEMENT #12;GTS-HPF Core Infiltration Experiment Experimental

  10. The sources and evolution of sulfur in the hypersaline Lake Lisan (paleo-Dead Sea)

    E-Print Network [OSTI]

    Torfstein, Adi

    mixolimnion), bacterial sulfate reduction (BSR) that occurred under the anoxic conditions of the lower brine reservoir in the lower brine was replenished by precipitation of gypsum from the upper layer, and its equation. Steady state d34 S values (~40x) were reached in the lower brine after long meromictic periods

  11. U.S. Department of the Interior U.S. Geological Survey

    E-Print Network [OSTI]

    Torgersen, Christian

    Graphite Peat Talc Beryllium Gypsum Perlite Tantalum Bismuth Hafnium Phosphate Rock Tellurium Boron Helium information on the USGS--the Federal source for science about the Earth, its natural and living resources--Reserves and Resources.....................193 Appendix D--Country Specialists Directory...............198 Mineral

  12. Iron and Steel Phosphate Rock

    E-Print Network [OSTI]

    Torgersen, Christian

    Kyanite Lead Lime Lithium Magnesium Manganese Mercury Mica Molybdenum Nickel Nitrogen Peat Perlite Graphite Peat Sulfur Beryllium Gypsum Perlite Talc Bismuth Hafnium Phosphate Rock Tantalum Boron Helium information on the USGS--the Federal source for science about the Earth, its natural and living resources

  13. Iron and Steel Phosphate Rock

    E-Print Network [OSTI]

    Torgersen, Christian

    Kyanite Lead Lime Lithium Magnesium Manganese Mercury Mica Molybdenum Nickel Nitrogen Peat Perlite Niobium Stone Barite Gold Nitrogen Strontium Bauxite Graphite Peat Sulfur Beryllium Gypsum Perlite Talc, its natural and living resources, natural hazards, and the environment: World Wide Web: http

  14. U.S. Department of the Interior U.S. Geological Survey

    E-Print Network [OSTI]

    Fleskes, Joe

    Graphite Peat Talc Beryllium Gypsum Perlite Tantalum Bismuth Hafnium Phosphate Rock Tellurium Boron Helium information on the USGS--the Federal source for science about the Earth, its natural and living resources--Reserves and Resources.....................193 Appendix D--Country Specialists Directory...............197 Mineral

  15. Oil and Gas Exploration

    E-Print Network [OSTI]

    Tingley, Joseph V.

    , oil and gas, and geothermal activities and accomplishments in Nevada: production statistics Products 23. Sloan dolomite quarry 24. Weiser gypsum quarry Oil Fields 1. Blackburn field 2. North WillowMetals Industrial Minerals Oil and Gas Geothermal Exploration Development Mining Processing Nevada

  16. Exchangeable sodium accumulation and replacement in Southeast Texas soils under turfgrass

    E-Print Network [OSTI]

    Najjar, Namir Fouad

    1995-01-01T23:59:59.000Z

    accumulation but exchangeable Na also increased as a function of years of irrigation. The multiple regression equation: SARE =-5.16 + 0.53 SARiw + 4.04 In (yr) (R2 = 0.86) best predicted SARE to a depth of 30 cm. This study also compared gypsum, a common...

  17. Appendix B: Wastes and Potential Hazards for

    E-Print Network [OSTI]

    Siddharthan, Advaith

    of minerals including gypsum, salt, potash, asbestos, graphite, fluorite, calcite, clay, sand and gravel or their compounds and should be considered under the following hazards: H5 to H7, H10, H11, or H14. 01 05 drilling muds and other drilling wastes 01 05 05* oil-containing drilling muds and wastes M Oil-containing muds

  18. Dept. of Soil A.J. Bussan

    E-Print Network [OSTI]

    Balser, Teri C.

    = CaCO3·MgCO3 Calcitic = CaCO3 Fly ash = CaO, Ca(OH2), CaCO3 Gypsum = CaSO4 CaCO3 + 2H+ = Ca2+ + CO2

  19. macla n 15. septiembre 2011 revista de la sociedad espaola de mineraloga

    E-Print Network [OSTI]

    Benning, Liane G.

    -rich waters leads to the formation of carbonate deposits: Ca2+ + CO32- CaCO3 (2) This coupled process to improve the understanding of the formation of CaCO3 phases through a detailed experimental study of gypsum dissolution and CaCO3 formation in the presence of Zn, Sr, Mg, or PO4 at 25°C. The purpose

  20. PORTSMOUTH HARBOR AND PISCATAQUA RIVER, NH & ME NAVIGATION IMPROVEMENT PROJECT

    E-Print Network [OSTI]

    US Army Corps of Engineers

    on the terminals located above Interstate 95. Cargoes include petroleum fuels, cement, gypsum, and liquid propane. The study evaluated project benefits based on reduction in transportation costs generated from a shift. The Recommended Plan will generate significant economic benefits for the nation, and is the National Economic

  1. Iron and Steel Phosphate Rock

    E-Print Network [OSTI]

    Torgersen, Christian

    Phosphate Rock Platinum Potash Pumice Quartz Crystal Rare Earths Rhenium Rubidium Salt Sand and Gravel Graphite Peat Sulfur Beryllium Gypsum Perlite Talc Bismuth Hafnium Phosphate Rock Tantalum Boron Helium on the USGS--the Federal source for science about the Earth, its natural and living resources, natural hazards

  2. Particle Size Distribution of Gypseous Samples

    E-Print Network [OSTI]

    Arnett, Morgan P.

    2010-01-16T23:59:59.000Z

    to conditions in the field. In order to understand the true characterization of the soil and the gypsum particles, the entire soil sample should be analyzed. Four different approaches to the BaCl2 method presented in the literature (Hesse, 1976, Matar...

  3. VOLUME 84, NUMBER 15 P H Y S I C A L R E V I E W L E T T E R S 10 APRIL 2000 Coherent Control of Absorption and Polarization Decay in a GaAs Quantum Well

    E-Print Network [OSTI]

    Hohng, Sung Chul

    , Renthof 5, D-35032 Marburg, Germany (Received 1 July 1999) Two phase-locked pulses are used to coherently of transform-limited pulses with a pulse duration of 150 fs. We produce two phase-locked collinear pulses excite excitonic polarizations. It is shown that the second pulse can either be strongly amplified

  4. Low-dimensional carbon nanotube and graphene devices

    E-Print Network [OSTI]

    Scard, Philip

    2010-10-12T23:59:59.000Z

    -jet printing of nanotubes directly onto GaAs. Although only one atom thick, graphene is macroscopic in area and must be patterned to confine conduction; room temperature transistor behaviour requires graphene ribbons only a few nanometres wide. This work...

  5. Monolithic heteroepitaxial integration of III-V semiconductor lasers on Si substrates

    E-Print Network [OSTI]

    Groenert, Michael

    2002-01-01T23:59:59.000Z

    Monolithic optoelectronic integration on silicon-based integrated circuits has to date been limited to date by the large material differences between silicon (Si) and the direct-bandgap GaAs compounds from which optoelectronic ...

  6. Nanopillar Photovoltaics: Photon Management and Junction Engineering for Next-Generation Solar Cells

    E-Print Network [OSTI]

    Mariani, Giacomo

    2013-01-01T23:59:59.000Z

    S. Heterojunction photovoltaics using GaAs nanowires andC. M. Single nanowire photovoltaics, Chem. Soc. Rev. 38, 16-nanopillar-array photovoltaics on low-cost and flexible

  7. Power dependence of pure spin current injection by quantum interference

    E-Print Network [OSTI]

    Ruzicka, Brian Andrew; Zhao, Hui

    2009-04-01T23:59:59.000Z

    We investigate the power dependence of pure spin current injection in GaAs bulk and quantumwell samples by a quantum interference and control technique. Spin separation is measured as a function of the relative strength of the two transition...

  8. RESEARCH/RESEARCHERS 4 MRS BULLETIN VOLUME 34 JANUARY 2009 www.mrs.org/bulletin

    E-Print Network [OSTI]

    Zhang, Xin

    wallpaper-Group Metamaterials Display Multiple Terahertz Resonances Metamaterials--artificial structures. A standard lift-off process was used to fabricate the metama- terials onto a semi-insulating (SI) GaAs wafer

  9. Limits and accuracy of valence force field models for In x Ga 1x N alloys Frank Grosse* and Jo rg Neugebauer

    E-Print Network [OSTI]

    to wurtzite are used as input, the model correctly describes the formation energies and structure of wurtzite'' semiconductors like GaAs and, as a consequence, the wurtzite crystal structure. Therefore, a purely elastic model

  10. Structure and electrical characterization of gallium arsenide nanowires with different V/III ratio growth parameters

    SciTech Connect (OSTI)

    Muhammad, R.; Ahamad, R. [Sustainability Research Alliance, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia); Ibrahim, Z.; Othaman, Z. [Physic Department, Faculty of Science, Universiti Teknologi Malaysia, 81310 Skudai, Johor (Malaysia)

    2014-03-05T23:59:59.000Z

    Gallium arsenide (GaAs) nanowires were grown vertically on GaAs(111)B substrate by gold-assisted using metal-organic chemical vapour deposition. Field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and conductivity atomic force microscopy (CAFM) analysis were carried out to investigate the effects of V/III ratio on structural properties and current-voltage changes in the wires. Results show that GaAs NWs grow preferably in the wurtzite crystal structure than zinc blende crystal structure with increasing V/III ratio. Additionally, CAFM studies have revealed that zincblende nanowires indicate ohmic characteristic compared to oscillation current occurred for wurtzite structures. The GaAs NWs with high quality structures are needed in solar cells technology for trapping energy that directly converts of sunlight into electricity with maximum capacity.

  11. 2008 Minerals Yearbook U.S. Department of the Interior

    E-Print Network [OSTI]

    , electronic warfare, and phased array radar. The ONR program's objectives were to extend the use of the high voltage Gaas pseudomorphic high electron mobility transistor (pHmET) technology to higher frequencies

  12. Technical Session II Talks | U.S. DOE Office of Science (SC)

    Office of Science (SC) Website

    .pdf file (6.2MB) GaAs Detector (Durbin) .pdf file (450KB) Advanced Neutron Detectors (Smith) .pdf file (818KB) Neutron Imaging System (Bingham) .pdf file (1.1MB) SR Advanced...

  13. European PVSECE Glasgow, Scotland 2000 III-V SPACE SOLAR CELLS ON Si SUBSTRATES USING GRADED GeSi BUFFERS

    E-Print Network [OSTI]

    As directly grown on Si, rendering the GaAs useless as a photovoltaic material. Nevertheless, many groups have, this dislocation density has still limited the minority carrier lifetimes obtained to ~ 1-3 ns, even after hydrogen

  14. PHYSICAL REVIEW B 83, 235311 (2011) First-principles electronic structure and relative stability of pyrite and marcasite

    E-Print Network [OSTI]

    Ceder, Gerbrand

    2011-01-01T23:59:59.000Z

    -scale photovoltaic applications, pyrite is ranked number one among all practical or promising thin-film solar cell orders of magnitude and even direct-gap materials such as GaAs. In a recent cost analysis for large

  15. Ferromagnetism in Co-doped (La,Sr)TiO3

    E-Print Network [OSTI]

    Fix, T.

    2010-01-01T23:59:59.000Z

    ordering in a diluted magnetic semiconductor Adv. Mater. 16,1], dilute magnetic semiconductors (DMSs) have been underAs: A new diluted magnetic semiconductor based on GaAs Appl.

  16. ambrym island vanuatu: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    subpicosecond carrier dynamics C. Kadowa) Materials; accepted for publication 5 October 1999 We report the growth of self-assembled ErAs islands embedded in GaAs by molecular beam...

  17. aphae island shinan-gun: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    subpicosecond carrier dynamics C. Kadowa) Materials; accepted for publication 5 October 1999 We report the growth of self-assembled ErAs islands embedded in GaAs by molecular beam...

  18. aphaedo island shinan-gun: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    subpicosecond carrier dynamics C. Kadowa) Materials; accepted for publication 5 October 1999 We report the growth of self-assembled ErAs islands embedded in GaAs by molecular beam...

  19. anticosti island laurentia: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    subpicosecond carrier dynamics C. Kadowa) Materials; accepted for publication 5 October 1999 We report the growth of self-assembled ErAs islands embedded in GaAs by molecular beam...

  20. aegna island tallinn: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    subpicosecond carrier dynamics C. Kadowa) Materials; accepted for publication 5 October 1999 We report the growth of self-assembled ErAs islands embedded in GaAs by molecular beam...

  1. Exchange Control of Nuclear Spin Diffusion in a Double Quantum Dot

    E-Print Network [OSTI]

    Reilly, D. J.

    The influence of gate-controlled two-electron exchange on the relaxation of nuclear polarization in small ensembles (N?10[superscript 6]) of nuclear spins is examined in a GaAs double quantum dot system. Waiting in the ...

  2. Outdoor Performance of a Thin-Film Gallium-Arsenide Photovoltaic Module

    SciTech Connect (OSTI)

    Silverman, T. J.; Deceglie, M. G.; Marion, B.; Cowley, S.; Kayes, B.; Kurtz, S.

    2013-06-01T23:59:59.000Z

    We deployed a 855 cm2 thin-film, single-junction gallium arsenide (GaAs) photovoltaic (PV) module outdoors. Due to its fundamentally different cell technology compared to silicon (Si), the module responds differently to outdoor conditions. On average during the test, the GaAs module produced more power when its temperature was higher. We show that its maximum-power temperature coefficient, while actually negative, is several times smaller in magnitude than that of a Si module used for comparison. The positive correlation of power with temperature in GaAs is due to temperature-correlated changes in the incident spectrum. We show that a simple correction based on precipitable water vapor (PWV) brings the photocurrent temperature coefficient into agreement with that measured by other methods and predicted by theory. The low operating temperature and small temperature coefficient of GaAs give it an energy production advantage in warm weather.

  3. In-situ deposition of high-k dielectrics on III-V compound semiconductor in MOCVD system

    E-Print Network [OSTI]

    Cheng, Cheng-Wei, Ph.D. Massachusetts Institute of Technology

    2010-01-01T23:59:59.000Z

    In situ deposition of high-k materials to passivate the GaAs in metal organic chemical vapor deposition (MOCVD) system was well demonstrated. Both atomic layer deposition (ALD) and chemical vapor deposition (CVD) methods ...

  4. Investigation of the GaN-on-GaAs interface for vertical power device applications

    SciTech Connect (OSTI)

    Möreke, Janina, E-mail: janina.moereke@bristol.ac.uk; Uren, Michael J.; Kuball, Martin [H.H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Novikov, Sergei V.; Foxon, C. Thomas [Department of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Hosseini Vajargah, Shahrzad; Wallis, David J.; Humphreys, Colin J. [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Haigh, Sarah J. [Super STEM Laboratory, STFC Daresbury Campus, Keckwick Lane, Daresbury WA4 4AD (United Kingdom); School of Materials, University of Manchester, Manchester M13 9PL (United Kingdom); Al-Khalidi, Abdullah; Wasige, Edward; Thayne, Iain [School of Engineering, University of Glasgow, Rankine Bldg, Oakfield Avenue, Glasgow G12 8LT (United Kingdom)

    2014-07-07T23:59:59.000Z

    GaN layers were grown onto (111) GaAs by molecular beam epitaxy. Minimal band offset between the conduction bands for GaN and GaAs materials has been suggested in the literature raising the possibility of using GaN-on-GaAs for vertical power device applications. I-V and C-V measurements of the GaN/GaAs heterostructures however yielded a rectifying junction, even when both sides of the junction were heavily doped with an n-type dopant. Transmission electron microscopy analysis further confirmed the challenge in creating a GaN/GaAs Ohmic interface by showing a large density of dislocations in the GaN layer and suggesting roughening of the GaN/GaAs interface due to etching of the GaAs by the nitrogen plasma, diffusion of nitrogen or melting of Ga into the GaAs substrate.

  5. The Effect of Offcut Angle on Electrical Conductivity of Direct Wafer-Bonded n-GaAs/n-GaAs Structures for Wafer-Bonded Tandem Solar Cells

    E-Print Network [OSTI]

    Yeung, King Wah Sunny

    2012-01-01T23:59:59.000Z

    Efficiency of p?n Junction Solar Cells, J. Appl. Phys. 32,Inverted Triple- Junction Solar Cell with Two Independentlyof Thin-Film GaAs Solar Cells on Si Substrates, J. Appl.

  6. Substrate engineering for monolithic integration of III-V semiconductors with Si CMOS technology

    E-Print Network [OSTI]

    Dohrman, Carl Lawrence

    2008-01-01T23:59:59.000Z

    Ge virtual substrates, fabricated using Si1-xGex-.Ge, compositionally graded buffers, enable the epitaxial growth of device-quality GaAs on Si substrates, but monolithic integration of III-V semiconductors with Si CMOS ...

  7. Fabrication of Molecular Devices 

    E-Print Network [OSTI]

    Walton, Katherine

    2011-08-04T23:59:59.000Z

    This project focuses on the synthesis and attachment of metal nanoparticles to Au and GaAs surfaces using a combination of chemical self-assembly and scanned probe lithography. In this project self-assembled monolayers (SAMs) of alkanethiols...

  8. Solid-State ElectronicsVol. 39, No. 2, pp. 311-313, 1996 Copyright 1996Elsevier Science Ltd

    E-Print Network [OSTI]

    Florida, University of

    utilized to realize these low-threshold devices, including InGaAs/InGaAsP[l-4], InGaAs/InGaP[2], GaAs/ AIGa

  9. Materials properties and dislocation dynamics in InAsP compositionally graded buffers on InP substrates

    E-Print Network [OSTI]

    .1063/1.4804264 Relaxed, high-quality InP on GaAs by using InGaAs and InGaP graded buffers to avoid phase separation J

  10. Nanopillar Photovoltaics: Photon Management and Junction Engineering for Next-Generation Solar Cells

    E-Print Network [OSTI]

    Mariani, Giacomo

    2013-01-01T23:59:59.000Z

    F. The influence of the InGaP window of GaAs solar cells,F. The influence of the InGaP window layer on the opticalEnhanced PCE using InGaP passivation…………………. ……..…. …………

  11. 1052 IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 14, NO. 8, AUGUST 2002 Temperature Sensitivity of 1300-nm InGaAsN

    E-Print Network [OSTI]

    Gilchrist, James F.

    @cae.wisc.edu). Publisher Item Identifier S 1041-1135(02)06012-3. compensating GaAs P barriers and n-InGaP­GaAsP tensile

  12. 4. international workshop on expert evaluation and control of compound semiconductor materials and technologies (EXMATEC `98): Conference program, abstracts and exhibition guide

    SciTech Connect (OSTI)

    NONE

    1998-06-01T23:59:59.000Z

    Partial contents include: Latest developments in VGF technology -- GaAs InP, and GaP; Photoelastic characterization of residual strain in GaAs wafers annealed in different holder geometrics; Nondestructive mode index measurement using resonant coupling; X-ray characterization of InP substrates; Reliability issues due to hot electrons in GaAs and InP HEMTS; Optical and structural analysis of degraded high power in InGaAlAs/As/AlGaAs lasers; Failure analysis of heavily proton irradiated InGaP solar cells by EBIC and cathodoluminescence; Electron irradiation and thermal annealing effects on GaAs solar cells; Structural characterization of InGaP/GaAs heterojunction bipolar transistors; III-Nitrides for red and IR applications; and Large area GaN substrates.

  13. Defect structures in rapidly degraded InGaAsP/InGaP double-heterostructure lasers

    SciTech Connect (OSTI)

    Ueda, O.; Wakao, K.; Yamaguchi, A.; Isozumi, S.; Komiya, S.

    1985-03-01T23:59:59.000Z

    Rapidly degraded InGaAsP/InGaP double-heterostructure lasers grown on (001)-oriented GaAs substrates by liquid phase epitaxy have been investigated by photolumi

  14. Theoretical analysis of strain and strain decay in InAs/GaAs,,001... multilayer quantum dot growth

    E-Print Network [OSTI]

    As or is assumed to change linearly from 50% at the bottom to 100% at the top. The exact QD dimensions GaAs spacer layers typically 20 nm . In these cases not only the effects of In migration

  15. anisotropic magnetoresistive sensor: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Israel (Received 14 March 1996) A periodic array of cylindrical voids, embedded in a thin film of n-doped GaAs, displays a pronounced anisotropy of the classical...

  16. Electronic Structure and Magnetism in Diluted Magnetic Semiconductors

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    like Mn, Fe, or Co having a net spin into a semiconducting host such as GaAs, ZnO, or GaN. The interaction among these spins leads to ferromagnetic order at low temperatures,...

  17. Eighth Annual Student Research

    E-Print Network [OSTI]

    Southern California, University of

    Dongseok Kang Carbon-doped GaAs single junction solar cells grown in multilayer epitaxial assemblies (with and poster session 2:30 PM awards ceremony #12;Posters Graduate student posters Laura Bradley Encapsulation

  18. Charge detection in semiconductor nanostructures

    E-Print Network [OSTI]

    MacLean, Kenneth (Kenneth MacLean, III)

    2010-01-01T23:59:59.000Z

    In this thesis nanometer scale charge sensors are used to study charge transport in two solid state systems: Lateral GaAs quantum dots and hydrogenated amorphous silicon (a-Si:H). In both of these experiments we use ...

  19. New GaInP/GaAs/GaInAs, Triple-Bandgap, Tandem Solar Cell for High-Efficiency Terrestrial Concentrator Systems

    SciTech Connect (OSTI)

    Kurtz, S.; Wanlass, M.; Kramer, C.; Young, M.; Geisz, J.; Ward, S.; Duda, A.; Moriarty, T.; Carapella, J.; Ahrenkiel, P.; Emery. K.; Jones, K.; Romero, M.; Kibbler, A.; Olson, J.; Friedman, D.; McMahon, W.; Ptak, A.

    2005-11-01T23:59:59.000Z

    GaInP/GaAs/GaInAs three-junction cells are grown in an inverted configuration on GaAs, allowing high quality growth of the lattice matched GaInP and GaAs layers before a grade is used for the 1-eV GaInAs layer. Using this approach an efficiency of 37.9% was demonstrated.

  20. TOKAMAK REACTOR DESIGNS AS A FUNCTION OF ASPECT RATIO

    E-Print Network [OSTI]

    California at Los Angeles, University of

    GA­A23168 TOKAMAK REACTOR DESIGNS AS A FUNCTION OF ASPECT RATIO by C.P.C. WONG and R.D. STAMBAUGH or reflect those of the United States Government or any agency thereof. #12;GA­A23168 TOKAMAK REACTOR DESIGNS JULY 1999 #12;C.P.C. WONG AND R.D. STAMBAUGH TOKAMAK REACTOR DESIGNS AS A FUNCTION OF ASPECT RATIO

  1. Delivered by Ingenta to: Sung Kyun Kwan University

    E-Print Network [OSTI]

    Boo, Jin-Hyo

    of solar cells, dye-sensitized solar cells (DSSC) have been of particular interest.4­6 In DSSC, dye and the low cost of TiO2 compared to GaAs, CdTe, and Si, a lower cost of DSSC is expected. However, efficiency of TiO2- based DSSC has been shown to be lower than those of GaAs-, CdTe-, and Si-based solar cells

  2. Effect of MnAs/GaAs(001) film accommodations on the phase-transition temperature

    SciTech Connect (OSTI)

    Iikawa, F.; Brasil, M.J.S.P.; Couto, O.D.D.; Adriano, C.; Giles, C.; Daeweritz, L. [Instituto de Fisica 'Gleb Wataghin', UNICAMP, Campinas-SP, C.P. 6165, 13083-970 (Brazil); Instituto de Fisica 'Gleb Wataghin', UNICAMP, Campinas-SP, C.P. 6165, 13083-970, Brazil and Laboratorio Nacional de Luz Sincrotron, CP-6192, 13084-971 Campinas-SP (Brazil); Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2004-09-20T23:59:59.000Z

    The phase-transition temperature of MnAs epitaxial films grown by molecular-beam epitaxy on GaAs(001) with different crystalline accommodations was studied by specular and grazing incidence x-ray diffraction. The transition temperature of MnAs films with tilted hexagonal c-axis orientations with respect to the GaAs substrate is higher than the most investigated nontilted films and reaches a value above room temperature, which is more suitable for device applications.

  3. Monitoring interfacial dynamics by pulsed laser techniques

    SciTech Connect (OSTI)

    Richmond, G.L.

    1991-01-01T23:59:59.000Z

    Goal is to develop new optical methods for the study of dynamic processes at the electrode/electrolyte interface. In the past year, optical second harmonic generation was used for time resolved measurements of thallium electrodeposition on Cu(111). Other studies included the study of the photochemistry involved in a GaAs surface treatment known as photowashing, and the study of picosecond time resolved luminescence decays from GaAs in electrochemical environments (power dependent effects). 4 figs. (DLC)

  4. Monitoring interfacial dynamics by pulsed laser techniques. Third yearly progress report

    SciTech Connect (OSTI)

    Richmond, G.L.

    1991-12-31T23:59:59.000Z

    Goal is to develop new optical methods for the study of dynamic processes at the electrode/electrolyte interface. In the past year, optical second harmonic generation was used for time resolved measurements of thallium electrodeposition on Cu(111). Other studies included the study of the photochemistry involved in a GaAs surface treatment known as photowashing, and the study of picosecond time resolved luminescence decays from GaAs in electrochemical environments (power dependent effects). 4 figs. (DLC)

  5. Direct modulation and optical confinement factor modulation of semiconductor lasers

    E-Print Network [OSTI]

    Luryi, Serge

    , an 80 Å In0.2Ga0.8As quantum well, a 0.1 m undoped GaAs optical confinement layer, a 1.2 m p InGaP, and etched off the p GaAs cap layer and 1.1 m out of the 1.2 m p InGaP cladding layer. The three ridges

  6. 444 IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 14, NO. 4, APRIL 2002 Low-Threshold Strain-Compensated InGaAs(N)

    E-Print Network [OSTI]

    Gilchrist, James F.

    lasers utilizing strain-compensating InGaP­GaAsP buffer layers and GaAs0 85P0 15 barrier layers, grownGaAs lower cladding layers, are significantly improved through the use of an InGaP­GaAsP buffer layer. II As and p-In Ga P, respectively. Buffer layers of 2650-Å n-InGaP ( ppm), and 20-Å highly-tensile GaAs P

  7. Scanning probe microscopy studies of semiconductor surfaces

    SciTech Connect (OSTI)

    Weinberg, W.H. [Univ. of California, Santa Barbara, CA (United States)

    1996-10-01T23:59:59.000Z

    Recent work involving atomic force microscopy and scanning tunneling microscopy is discussed which involves strain-induced, self-assembling nanostructures in compound semiconductor materials. Specific examples include one-dimensional quantum wires of InAs grown by MBE on GaAs(001) and zero-dimensional quantum dots of InP grown by MOCVD on InGaP which is lattice matched to GaAs(001).

  8. Investigation of MOVPE-grown GaN layers doped with As atoms A. F. Tsatsul'nikov, B. Ya. Ber, A. P. Kartashova, Yu. A. Kudryavtsev, N. N. Ledentsov,

    E-Print Network [OSTI]

    Nabben, Reinhard

    Investigation of MOVPE-grown GaN layers doped with As atoms A. F. Tsatsul'nikov, B. Ya. Ber, A. P vapor-phase epitaxy. It is shown that the deposition of GaAs on a GaN surface relieves stresses in the GaN layer. The high-temperature overgrowth of a thin GaAs layer by a GaN layer causes As atoms

  9. Journal of Electronic Materials, Vol. 17, No. 5, 1988 Effect of Iso-Electronic

    E-Print Network [OSTI]

    Woodall, Jerry M.

    Journal of Electronic Materials, Vol. 17, No. 5, 1988 Effect of Iso-Electronic GaAs Dopants that addition of either one of these two iso-electronic dopants has a similar effect on the solid stoichiometry it is also shown that the addition of the iso-electronic dopants A1 or P to GaAs would not result in the same

  10. Skin thickness effects on in vivo LXRF

    SciTech Connect (OSTI)

    Preiss, I.L.; Washington, W. II [Rensselaer Polytechnic Inst., Troy, NY (United States)

    1995-12-31T23:59:59.000Z

    The analysis of lead concentration in bone utilizing LXRF can be adversely effected by overlying issue. A quantitative measure of the attenuation of the 10.5 keV Pb L a x-ray signal by skin and skin equivalent plastic has been conducted. Concentration ranges in plaster of Paris and goat bone from 7 to 90 ppm with attenuators of Lucite{reg_sign} and pig skin were examined. It is concluded that no quantitative or semi quantitative analysis can be achieved if overlying sue thickness exceeds 3 mm for Ph concentrations of less than 30 porn Ph in bone.

  11. Acoustic probing of salt using sonar

    E-Print Network [OSTI]

    Butler, Kenneth Bryan

    1977-01-01T23:59:59.000Z

    , glycerine, and s1li cone oil provi ded satisfactory performance. In spite of these results, Gupta did not develop a workable means of us1ng 11quid coupl1ng media under mine condit1ons. In his field tests, Gupta used dental impression plaster (a coupling... acoustic pulses which are coupled 1nto the salt via a castor oil coupling medium. The acoustic source signa'i is a square-enveloped pulse of compress1onal waves; a pulse duration of e1ther 0. 3 ms or 1. 1 ms is used. The ranges to discontinuities...

  12. Formosan Subterranean Termites 

    E-Print Network [OSTI]

    Gold, Roger E.; Glenn, Grady J.; Howell Jr., Harry N.; Keck, Molly

    2005-12-05T23:59:59.000Z

    be properly fumigated to prevent termites from traveling within them and infesting the soil at a landscaping site. Cargo pallets that have rested on infested soil as well as mulch and sod from infested areas have also spread the Formosan termite into Texas... is associated with mud-like carton material. Like other subterranean termites, when searching for food and moisture, they may chew through non-cellulose material, such as asphalt, plaster, creosote, rubber and plastic. Signs of infestation The presence of mud...

  13. Influence of two calcium sources on the growth and nodulation of two tropical legumes 

    E-Print Network [OSTI]

    Wood Euceda, Miriam Jeannette

    1986-01-01T23:59:59.000Z

    1. 77 a 2. 04 a 2. 11 a 2. 02 a 1. 88 ab 1. 71 a 1. 98 ab 2. 48 c 2. 08 b Means withsn co umns wi t e same etter are not significantly different by Ouncans multiple range test at P=0. 05. 3. 0 . SAND a H GYPSUM CI LIME 2. 4 Z 1. 8 O... to study the effect of varying the Al/Ca ratio of acid soils, by adding lime or a neutral salt (gypsum), on the establishment and nodulation of tropical legumes. The soils used were a Hearne clay (pH 4. 7), and a Silstid loamy fine sand (pH 4. 6). Lime...

  14. Pilot-Scale Demonstration of hZVI Process for Treating Flue Gas Desulfurization Wastewater at Plant Wansley, Carrollton, GA

    E-Print Network [OSTI]

    Peddi, Phani 1987-

    2011-12-06T23:59:59.000Z

    materials. These solids are flushed using high pressure jet stream which will fluidise the carbon bed dislodging the particles fixed in the carbon bed. The backwash water should be treated prior to discharge as the concentrations of the pollutants...). This slurry containing gypsum is recycled using recycle pumps and pumped to different levels and sprayed down. This slurry is continuously re-circulated until the percentage of solids and chlorides concentration raises up to certain level. Then a blowdown...

  15. Salinity Control in Irrigation Agriculture.

    E-Print Network [OSTI]

    Lyerly, Paul J.; Longenecker, Donald E.

    1962-01-01T23:59:59.000Z

    streams and under- ground sources contain dissolved substances known chemically as salts. Ocean water contains approximately 3 percent salts, or 40 tons of salts per acre-foot of water. Waters used for irriga- tion generally contain .1 to 5 tons... of salt per acre-foot of water. In general terms, salt is thought of as table alt; however, thousands of different salts are known. Examples of common salts in irrigation water are table salt (sodium chloride), Epsom salt (magnesium sulfate), gypsum...

  16. Covering Walls With Fabrics.

    E-Print Network [OSTI]

    Anonymous,

    1979-01-01T23:59:59.000Z

    TDOC . Z TA24S.7 8873 NO.1227 WALLS with ;FABRICS Texas Agricultural Extension Service . The Texas A&M University System Daniel C. Pfannstiel, Director, College Station, Texas Covering Walls with Fabrics* When tastefully applied, fabrics... it is applied, fabric-covered walls improve the sound-absorbing acoustical properties of a room. Also, fabrics can be used for covering walls of either textured gypsum board or wood paneling. Home decorating magazines are good sources for ideas about fabric...

  17. Experimental and Analytical Research on Fracture Processes in ROck

    SciTech Connect (OSTI)

    Herbert H.. Einstein; Jay Miller; Bruno Silva

    2009-02-27T23:59:59.000Z

    Experimental studies on fracture propagation and coalescence were conducted which together with previous tests by this group on gypsum and marble, provide information on fracturing. Specifically, different fracture geometries wsere tested, which together with the different material properties will provide the basis for analytical/numerical modeling. INitial steps on the models were made as were initial investigations on the effect of pressurized water on fracture coalescence.

  18. Irrigation Water Quality Salinity Management

    E-Print Network [OSTI]

    Small Potassium sulfate K2SO4 Small Sodium bicarbonate NaHCO3 Small Calcium carbonate CaCO3 Very Small concentration as related to the concentration of calcium and magnesium, and 3 Irrigation Water Quality Standards Na2SO4 Moderate to large Calcium chloride CaCl2 Moderate Calcium sulfate (gypsum) CaSO4 2H2O Moderate

  19. Reservoir simulation of co2 sequestration and enhanced oil recovery in Tensleep Formation, Teapot Dome field 

    E-Print Network [OSTI]

    Gaviria Garcia, Ricardo

    2006-04-12T23:59:59.000Z

    ............................................................................. 58 1 CHAPTER I 2. INTRODUCTION 1.1 Background Teapot Dome field, also known as Naval Petroleum Reserve #3 (NPR-3) is located in the southwest portion of the Powder River Basin, 35 miles north of Casper, Wyoming... through the reservoir, precipitates such as gypsum can form.5 12 CHAPTER III 2. GEOLOGY REVIEW 3.1 Introduction Teapot Dome also known as the Naval Petroleum Reserve No. 3 (NPR-3) is located in central Wyoming, near...

  20. Sub-surface dissolution of evaporites in the Eastern Mediterranean sea

    E-Print Network [OSTI]

    Camerlenghi, Angelo Alessandro

    1988-01-01T23:59:59.000Z

    in Bryant et al. (1981) Figure 9. Simplified scheme of the typical Messinian series of the Cattolica Basin (Sicily, Italy) atter Decima and Wezel (1973) . Figure 10. Dissolution of gypsum and anhydrite in NaCI solution and in seawater at 1 Atm pressure... phenomenon that can be defined as submarine karst. CHAPTER I I BACKGROUND The Problem of the Cobblestone Topography The area of interest for this work is the Mediterranean Ridge, a complex of thrusted sediments interpreted as an accretionary prism...

  1. Efficient photon extraction from a quantum dot in a broad-band planar cavity antenna

    SciTech Connect (OSTI)

    Ma, Yong, E-mail: y.ma@hw.ac.uk; Kremer, Peter E.; Gerardot, Brian D., E-mail: B.D.Gerardot@hw.ac.uk [Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom)

    2014-01-14T23:59:59.000Z

    We analyse the extraction of photons emitted from single InAs quantum dots embedded in planar microcavities. The structures are designed to achieve broad-band operation and high-collection efficiency from a device requiring straightforward fabrication, even with electrical contacts. The designs consist of a quantum dot in a GaAs membrane with asymmetric top and bottom mirrors and a top-side solid immersion lens (SIL). Four separate cases are considered in our design: a GaAs membrane only (case 1), GaAs membrane with a glass SIL on top (case 2), a GaAs membrane with a glass SIL on top and a back mirror consisting of Au (case 3), a GaAs membrane with a glass SIL on top of a distribute Bragg reflector mirror and Au back mirror (case 4). Both finite difference time domain and analytical simulations are used to calculate the electric field, power density, and far-field radiation pattern. For optimized structures (case 4), we obtain significant extraction efficiencies (>50%) with modest Purcell enhancements (?20%) and a large spectral full-width-half-maximum (>100?nm). The high-extraction efficiency, broad-band operation, and facile fabrication make the proposed structures promising for realistic quantum dot devices.

  2. TBM tunnel friction values for the Grizzly Powerhouse Project

    SciTech Connect (OSTI)

    Stutsman, R.D. [Ensign & Buckley Consulting Engineers, Larkspur, CA (United States); Rothfuss, B.D. [Pacific Gas and Electric Co., San Francisco, CA (United States)

    1995-12-31T23:59:59.000Z

    Tunnel boring machine (TBM) driven water conveyance tunnels are becoming increasingly more common. Despite advances in tunnel engineering and construction technology, hydraulic performance data for TBM driven tunnels remains relatively unavailable. At the Grizzly Powerhouse Project, the TBM driven water conveyance tunnel was designed using friction coefficients developed from a previous PG&E project. A range of coefficients were selected to bound the possible hydraulic performance variations of the water conveyance system. These friction coefficients, along with the water conveyance systems characteristics, and expected turbine characteristics, were used in a hydraulic transient analysis to determine the expected system pressure fluctuations, and surge chamber performance. During startup test data, these performance characteristics were measured to allow comparison to the original design assumptions. During construction of the tunnel, plaster casts were made of the actual excavated tunnel unlined and fiber reinforced shotcrete lined surfaces. These castings were used to measure absolute roughness of the surfaces so that a friction coefficient could be developed using the Moody diagram and compare them against the design values. This paper compares the assumed frictional coefficient with computed coefficients from headlosses measured during startup testing, and plaster cast measurement calculations. In addition, a comparison of coefficients will be presented for an other TBM driven water conveyance tunnel constructed in the 1980`s.

  3. Improved substrate structures for InP-based devices

    SciTech Connect (OSTI)

    Wanlass, M.; Sheldon, P.

    1988-09-30T23:59:59.000Z

    A substrate structure for an InP-based semiconductor device having an InP-based film is disclosed. The substrate structure includes a substrate region having a light-weight bulk substrate and an upper GaAs layer. An interconnecting region is disposed between the substrate region and the InP-based device. The interconnecting region includes a compositionally graded intermediate layer substantially lattice matched at its one end to the GaAs layer and substantially lattice matched at its opposite end to the InP-based film. The interconnecting region further includes a dislocation mechanism disposed between the GaAs layer and the InP-based film in cooperation with the graded intermediate layer, the buffer mechanism blocking and inhibiting propagation of threading dislocations between the substrate region and the InP-based device. 1 fig.

  4. Substrate structures for InP-based devices

    SciTech Connect (OSTI)

    Wanlass, Mark W. (Golden, CO); Sheldon, Peter (Lakewood, CO)

    1990-01-01T23:59:59.000Z

    A substrate structure for an InP-based semiconductor device having an InP based film is disclosed. The substrate structure includes a substrate region having a lightweight bulk substrate and an upper GaAs layer. An interconnecting region is disposed between the substrate region and the InP-based device. The interconnecting region includes a compositionally graded intermediate layer substantially lattice-matched at one end to the GaAs layer and substantially lattice-matched at the opposite end to the InP-based film. The interconnecting region further includes a dislocation mechanism disposed between the GaAs layer and the InP-based film in cooperation with the graded intermediate layer, the buffer mechanism blocking and inhibiting propagation of threading dislocations between the substrate region, and the InP-based device.

  5. Mean transverse energy and response time measurements of GaInP based photocathodes

    SciTech Connect (OSTI)

    Jin, Xiuguang [Institute for Advanced Research, Nagoya University, Nagoya 464-8603 (Japan); Yamamoto, Masahiro; Miyajima, Tsukasa; Honda, Yosuke; Uchiyama, Takashi [High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801 (Japan); Tabuchi, Masao [Nagoya University Synchrotron Radiation Research Center, Nagoya 464-8603 (Japan); Takeda, Yoshikazu [Nagoya Industrial Science Research Institute, Nagoya 464-0819 (Japan); Aichi Synchrotron Radiation Center, Aichi Science and Technology Foundation, Seto 489-0965 (Japan)

    2014-08-14T23:59:59.000Z

    GaInP, which has a wider band gap than GaAs, is introduced as a photocathode for energy recovery linac (ERL). The wide band gap of material is expected to reduce the heating effect in the thermal relaxation process after high energy excitation. GaInP photocathodes exhibited higher quantum efficiency than GaAs and low thermal emittance as the same as GaAs photocathodes under green laser light irradiation. A short picosecond electron pulse was also achieved with the GaInP photocathode under 532?nm pulse laser irradiation. These experimental results demonstrate that the GaInP photocathode is an important candidate for ERL.

  6. Ultra-high frequency photoconductivity decay in GaAs/Ge/GaAs double heterostructure grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Hudait, M. K.; Zhu, Y. [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Johnston, S. W. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)] [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Maurya, D.; Priya, S. [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Umbel, R. [Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)

    2013-03-04T23:59:59.000Z

    GaAs/Ge/GaAs double heterostructures (DHs) were grown in-situ using two separate molecular beam epitaxy chambers. High-resolution x-ray rocking curve demonstrates a high-quality GaAs/Ge/GaAs heterostructure by observing Pendelloesung oscillations. The kinetics of the carrier recombination in Ge/GaAs DHs were investigated using photoconductivity decay measurements by the incidence excitation from the front and back side of 15 nm GaAs/100 nm Ge/0.5 {mu}m GaAs/(100)GaAs substrate structure. High-minority carrier lifetimes of 1.06-1.17 {mu}s were measured when excited from the front or from the back of the Ge epitaxial layer, suggests equivalent interface quality of GaAs/Ge and Ge/GaAs. Wavelength-dependent minority carrier recombination properties are explained by the wavelength-dependent absorption coefficient of Ge.

  7. X-ray photoelectron spectroscopy of gallium nitride films grown by radical-beam gettering epitaxy

    SciTech Connect (OSTI)

    Rogozin, I. V. [Berdyansk State Pedagogical University (Ukraine)], E-mail: rogozin@bdpu.org; Kotlyarevsky, M. B. [Academy of Management and Information Technology (Ukraine)

    2007-05-15T23:59:59.000Z

    Thin GaN films were grown on GaAs(111) substrates by radical-beam gettering epitaxy. The structural quality of the films was studied by high-resolution x-ray diffraction. The chemical composition of the GaAs surface and GaN film was studied by x-ray photoelectron spectroscopy. It is shown that Ga-N and As-N bonds are formed on the GaAs surface at initial growth stages at low temperatures. The state of the film-substrate interface was studied. It was found that prolonged annealing of GaN films in nitrogen radicals shifts the composition to nitrogen excess.

  8. APPLIED PHYTO-REMEDIATION TECHNIQUES USING HALOPHYTES FOR OIL AND BRINE SPILL SCARS

    SciTech Connect (OSTI)

    M.L. Korphage; Bruce G. Langhus; Scott Campbell

    2003-03-01T23:59:59.000Z

    Produced salt water from historical oil and gas production was often managed with inadequate care and unfortunate consequences. In Kansas, the production practices in the 1930's and 1940's--before statewide anti-pollution laws--were such that fluids were often produced to surface impoundments where the oil would segregate from the salt water. The oil was pumped off the pits and the salt water was able to infiltrate into the subsurface soil zones and underlying bedrock. Over the years, oil producing practices were changed so that segregation of fluids was accomplished in steel tanks and salt water was isolated from the natural environment. But before that could happen, significant areas of the state were scarred by salt water. These areas are now in need of economical remediation. Remediation of salt scarred land can be facilitated with soil amendments, land management, and selection of appropriate salt tolerant plants. Current research on the salt scars around the old Leon Waterflood, in Butler County, Kansas show the relative efficiency of remediation options. Based upon these research findings, it is possible to recommend cost efficient remediation techniques for slight, medium, and heavy salt water damaged soil. Slight salt damage includes soils with Electrical Conductivity (EC) values of 4.0 mS/cm or less. Operators can treat these soils with sufficient amounts of gypsum, install irrigation systems, and till the soil. Appropriate plants can be introduced via transplants or seeded. Medium salt damage includes soils with EC values between 4.0 and 16 mS/cm. Operators will add amendments of gypsum, till the soil, and arrange for irrigation. Some particularly salt tolerant plants can be added but most planting ought to be reserved until the second season of remediation. Severe salt damage includes soil with EC values in excess of 16 mS/cm. Operators will add at least part of the gypsum required, till the soil, and arrange for irrigation. The following seasons more gypsum will be added and as the soil EC is reduced, plants can be introduced. If rapid remediation is required, a sufficient volume of topsoil, or sand, or manure can be added to dilute the local salinity, the bulk amendments tilled into the surface with added gypsum, and appropriate plants added. In this case, irrigation will be particularly important. The expense of the more rapid remediation will be much higher.

  9. Field Testing of Nano-PCM Enhanced Building Envelope Components

    SciTech Connect (OSTI)

    Biswas, Kaushik [ORNL; Childs, Phillip W [ORNL; Atchley, Jerald Allen [ORNL

    2013-08-01T23:59:59.000Z

    The U.S. Department of Energy s (DOE) Building Technologies Program s goal of developing high-performance, energy efficient buildings will require more cost-effective, durable, energy efficient building envelopes. Forty-eight percent of the residential end-use energy consumption is spent on space heating and air conditioning. Reducing envelope-generated heating and cooling loads through application of phase change material (PCM)-enhanced envelope components can facilitate maximizing the energy efficiency of buildings. Field-testing of prototype envelope components is an important step in estimating their energy benefits. An innovative phase change material (nano-PCM) was developed with PCM encapsulated with expanded graphite (interconnected) nanosheets, which is highly conducive for enhanced thermal storage and energy distribution, and is shape-stable for convenient incorporation into lightweight building components. During 2012, two test walls with cellulose cavity insulation and prototype PCM-enhanced interior wallboards were installed in a natural exposure test (NET) facility at Charleston, SC. The first test wall was divided into four sections, which were separated by wood studs and thin layers of foam insulation. Two sections contained nano-PCM-enhanced wallboards: one was a three-layer structure, in which nano-PCM was sandwiched between two gypsum boards, and the other one had PCM dispersed homogeneously throughout graphite nanosheets-enhanced gypsum board. The second test wall also contained two sections with interior PCM wallboards; one contained nano-PCM dispersed homogeneously in gypsum and the other was gypsum board containing a commercial microencapsulated PCM (MEPCM) for comparison. Each test wall contained a section covered with gypsum board on the interior side, which served as control or a baseline for evaluation of the PCM wallboards. The walls were instrumented with arrays of thermocouples and heat flux transducers. Further, numerical modeling of the walls containing the nano-PCM wallboards were performed to determine their actual impact on wall-generated heating and cooling loads. The models were first validated using field data, and then used to perform annual simulations using Typical Meteorological Year (TMY) weather data. This article presents the measured performance and numerical analysis to evaluate the energy-saving potential of the nano-PCM-enhanced building components.

  10. The structure of GaAs/Si(211) heteroepitaxial layers

    SciTech Connect (OSTI)

    Liliental-Weber, Z.; Weber, E.R.; Washburn, J.; Liu, T.Y.; Kroemer, H.

    1985-05-01T23:59:59.000Z

    Gallium arsenide films grown on (211)Si by molecular-beam epitaxy have been investigated using transmission electron microscopy. The main defects observed in the alloy were of misfit dislocations, stacking faults, and microtwin lamellas. Silicon surface preparation was found to play an important role on the density of defects formed at the Si/GaAs interface. Two different types of strained-layer superlattices, InGaAs/InGaP and InGaAs/GaAs, were applied either directly to the Si substrate, to a graded layer (GaP-InGaP), or to a GaAs buffer layer to stop the defect propagation into the GaAs films. Applying InGaAs/GaAs instead of InGaAs/InGaP was found to be more effective in blocking defect propagation. In all cases of strained-layer superlattices investigated, dislocation propagation was stopped primarily at the top interface between the superlattice package and GaAs. Graded layers and unstrained AlGaAs/GaAs superlattices did not significantly block dislocations propagating from the interface with Si. Growing of a 50 nm GaAs buffer layer at 505/sup 0/C followed by 10 strained-layer superlattices of InGaAs/GaAs (5 nm each) resulted in the lowest dislocation density in the GaAs layer (approx.5 x 10/sup 7//cm/sup 2/) among the structures investigated. This value is comparable to the recently reported density of dislocations in the GaAs layers grown on (100)Si substrates. Applying three sets of the same strained layers decreased the density of dislocations an additional approx.2 to 3 times.

  11. Suppression of nuclear spin diffusion at a GaAs/AlGaAs interface measured with a single quantum dot nano-probe

    E-Print Network [OSTI]

    A. E. Nikolaenko; E. A. Chekhovich; M. N. Makhonin; I. W. Drouzas; A. B. Vankov; J. Skiba-Szymanska; M. S. Skolnick; P. Senellart; A. Lemaitre; A. I. Tartakovskii

    2009-01-15T23:59:59.000Z

    Nuclear spin polarization dynamics are measured in optically pumped individual GaAs/AlGaAs interface quantum dots by detecting the time-dependence of the Overhauser shift in photoluminescence (PL) spectra. Long nuclear polarization decay times of ~ 1 minute have been found indicating inefficient nuclear spin diffusion from the GaAs dot into the surrounding AlGaAs matrix in externally applied magnetic field. A spin diffusion coefficient two orders lower than that previously found in bulk GaAs is deduced.

  12. Evaluation of growth methods for the heteroepitaxy of non-polar (11-20) GaN on sapphire by MOVPE

    E-Print Network [OSTI]

    Oehler, F.; Sutherland, D.; Zhu, T.; Emery, R.; Badcock, T. J.; Kappers, M. J.; Humphreys, C. J.; Dawson, P.; Oliver, R. A.

    2014-09-16T23:59:59.000Z

    double grating spectrometer equipped with a Peltier-cooled GaAs photomultiplier tube. The spectra were recorded with signal lock-in processing techniques. As the HeCd laser absorption length is ca. 350 nm for 99% absorption in GaN (ignoring any carrier... double grating spectrometer equipped with a Peltier-cooled GaAs photomultiplier tube. The spectra were recorded with signal lock-in processing techniques. As the HeCd laser absorption length is ca. 350 nm for 99% absorption in GaN (ignoring any carrier...

  13. Fabrication of optoelectronic microwave linear and ring resonators on a gallium arsenide substrate

    E-Print Network [OSTI]

    Yeh, Chun-Liang

    1993-01-01T23:59:59.000Z

    for the degree of MASTER OF SCIENCE August 1993 Major Subject: Electrical Engineering FABRICATION OF OPTOELECTRONIC MICROWAVE LINEAR AND RING RESONATORS ON A GALLIUM ARSENIDE SUBSTRATE A Thesis by CHUN-LIANG YEH Approved as to style and content by: Mark... and the first modes at 4. 87, 4. 89, 4. 91 GHz have been designed, simulated, and fabricated on a GaAs substrate. A microstrip ring resonator with 3/4 pm coupling gaps and the first mode at 3. 456 GHz also has been fabricated on GaAs. A reliable high yield...

  14. Current-matched high-efficiency, multijunction monolithic solar cells

    DOE Patents [OSTI]

    Olson, Jerry M. (Lakewood, CO); Kurtz, Sarah R. (Golden, CO)

    1993-01-01T23:59:59.000Z

    The efficiency of a two-junction (cascade) tandem photovoltaic device is improved by adjusting (decreasing) the top cell thickness to achieve current matching. An example of the invention was fabricated out of Ga.sub.0.52 In.sub.0.48 P and GaAs. Additional lattice-matched systems to which the invention pertains include Al.sub.x Ga.sub.1-x /GaAS (x= 0.3-0.4), GaAs/Ge and Ga.sub.y In.sub.l-y P/Ga.sub.y+0.5 In.sub.0.5-y As (0

  15. Strength of semiconductors, metals, and ceramics evaluated by a microscopic cleavage model with Morse-type and Lennard-Jones-type interaction

    SciTech Connect (OSTI)

    Hess, Peter [Institute of Physical Chemistry, University of Heidelberg, Im Neuenheimer Feld 253, D-69120 Heidelberg (Germany)

    2014-08-07T23:59:59.000Z

    An improved microscopic cleavage model, based on a Morse-type and Lennard-Jones-type interaction instead of the previously employed half-sine function, is used to determine the maximum cleavage strength for the brittle materials diamond, tungsten, molybdenum, silicon, GaAs, silica, and graphite. The results of both interaction potentials are in much better agreement with the theoretical strength values obtained by ab initio calculations for diamond, tungsten, molybdenum, and silicon than the previous model. Reasonable estimates of the intrinsic strength are presented for GaAs, silica, and graphite, where first principles values are not available.

  16. Narrow energy band gap gallium arsenide nitride semi-conductors and an ion-cut-synthesis method for producing the same

    DOE Patents [OSTI]

    Weng, Xiaojun; Goldman, Rachel S.

    2006-06-06T23:59:59.000Z

    A method for forming a semi-conductor material is provided that comprises forming a donor substrate constructed of GaAs, providing a receiver substrate, implanting nitrogen into the donor substrate to form an implanted layer comprising GaAs and nitrogen. The implanted layer is bonded to the receiver substrate and annealed to form GaAsN and nitrogen micro-blisters in the implanted layer. The micro-blisters allow the implanted layer to be cleaved from the donor substrate.

  17. Isoelectronic co-doping

    DOE Patents [OSTI]

    Mascarenhas, Angelo

    2004-11-09T23:59:59.000Z

    Isoelectronic co-doping of semiconductor compounds and alloys with deep acceptors and deep donors is used to decrease bandgap, to increase concentration of the dopant constituents in the resulting alloys, and to increase carrier mobilities lifetimes. Group III-V compounds and alloys, such as GaAs and GaP, are isoelectronically co-doped with, for example, N and Bi, to customize solar cells, thermal voltaic cells, light emitting diodes, photodetectors, and lasers on GaP, InP, GaAs, Ge, and Si substrates. Isoelectronically co-doped Group II-VI compounds and alloys are also included.

  18. Thickness dependence of magnetic anisotropy in thin Ni films electrodeposited onto the (011) and (001) surfaces of n-GaAs

    SciTech Connect (OSTI)

    Gubbiotti, G.; Carlotti, G.; Tacchi, S.; Liu, Y.-K.; Scheck, C.; Schad, R.; Zangari, G. [INFM CRS-SOFT, c/o Universita di Roma 'La Sapienza', I-00185, Rome (Italy); INFM UdR-Perugia, c/o Dipartimento di Fisica, Universita di Perugia, Via A. Pascoli, 06123 Perugia (Italy); INFM-National Center for nanoStructures and bioSystem at Surfaces (S3) Modena, and Dipartimento di Fisica, Universita di Perugia, Via A. Pascoli, 06123 Perugia (Italy); IINFM UdR-Perugia, Dipartimento di Fisica, Universita di Perugia, Via A. Pascoli, 06123 Perugia (Italy); MINT Center, University of Alabama, Tuscaloosa Alabama 35401 (United States); Department of Materials Science and Engineering and Center for Electrochemical Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States)

    2005-05-15T23:59:59.000Z

    Brillouin light scattering from thermal spin waves has been exploited to investigate the thickness dependence of magnetic anisotropy of Ni films, with thickness in the range 7-35 nm, grown by electrodeposition onto either (011)- or (001)-GaAs substrates. In the former case, Ni films exhibit a well-defined in-plane uniaxial anisotropy induced by the symmetry of the substrate. In the case of the (001)-GaAs substrate, instead, the magnetic anisotropy results from a combination of both a fourfold and a twofold contribution. The physical mechanisms responsible for the observed anisotropy, as well as its dependence on film thickness, are discussed in detail.

  19. Anisotropic reactive ion etching of vanadium dioxide 

    E-Print Network [OSTI]

    Radle, Byron K

    1990-01-01T23:59:59.000Z

    Facility for Submicron Structures, Cornell University, Ithaca, New York [7]. In these studies thin film VO2 was etched with a SF6/CO2 chemistry. SF6 chemistry was chosen because volatile vanadium fluorides can be formed easily. CO2 supplied the carbon... (Silicon Doped GaAs) Semi-Insulating GaAs Metal (AuGe, Ni, Au) Fig. 19. This is a step by step drawn representation of the fabrication procedure. 53 1. Pattern Photo Resist for Optical Stack etch mask. P Etched VOz in CFe plasma. 3. Etched Alz...

  20. Plasmon Enhancements for FIR Detection A. G. U. Perera, S. G. Matsik, P. V. V. Jayaweera

    E-Print Network [OSTI]

    Perera, A. G. Unil

    Plasmon Enhancements for FIR Detection A. G. U. Perera, S. G. Matsik, P. V. V. Jayaweera Department Council-Canada Ont. CANADA Abstract--The use of plasmons to improve the response of FIR and THz detectors is generating extensive interest. Increased absorption due to the plasmonic absorption in a GaAs wafer

  1. P. MCK Cryst. Res. Technol. 35 (2000) 529-540 Department of Materials, University of Oxford

    E-Print Network [OSTI]

    Moeck, Peter

    Comparison of Experiments and Theories for Plastic Deformation in thermally processed GaAs Wafers Different single crystal X-ray transmission topography, scanning infrared polariscopy, visible light interferometry that reduces the yield of electronic devices in manufacturing processes on an industrial scale [KIYAMA et al

  2. Optically initiated silicon carbide high voltage switch

    DOE Patents [OSTI]

    Caporaso, George J. (Livermore, CA); Sampayan, Stephen E. (Manteca, CA); Sullivan, James S. (Livermore, CA); Sanders; David M. (Livermore, CA)

    2011-02-22T23:59:59.000Z

    An improved photoconductive switch having a SiC or other wide band gap substrate material, such as GaAs and field-grading liners composed of preferably SiN formed on the substrate adjacent the electrode perimeters or adjacent the substrate perimeters for grading the electric fields.

  3. Optically-initiated silicon carbide high voltage switch

    DOE Patents [OSTI]

    Caporaso, George J. (Livermore, CA); Sampayan, Stephen E. (Manteca, CA); Sullivan, James S. (Livermore, CA); Sanders, David M. (Livermore, CA)

    2012-02-28T23:59:59.000Z

    An improved photoconductive switch having a SIC or other wide band gap substrate material, such as GaAs and field-grading liners composed of preferably SiN formed on the substrate adjacent the electrode perimeters or adjacent the substrate perimeters for grading the electric fields.

  4. TIME-RESOLVED TERAHERTZ TRANSMISSION SPECTROSCOPY OF DIELECTRICS

    E-Print Network [OSTI]

    Ku?el, Petr

    semiconductor surfaces in bulk semiconductor wafers[5,6,7], etc. The detection techniques which are based in fact constitutes a bridge between the classical IR spectroscopy domain and the frequencies accessible polar excitations in optical materials like sapphire and quartz[15], in semiconductors (Ge, GaAs, Si

  5. Low Cost RF MEMS Switches Fabricated on Microwave Laminate Printed Circuit Boards

    E-Print Network [OSTI]

    De Flaviis, Franco

    have been demonstrated with superior performance over conventional semiconductor devices [4. They are normally built on high-resistivity silicon wafers, GaAs wafers, and quartz substrates using semiconductor prior to deposition of a metal membrane bridge, which poses a major challenge to manufacturability

  6. IEEE ELECTRON DEVICE LETTERS, VOL. 24, NO. 4, APRIL 2003 227 RF MEMS Switches Fabricated on

    E-Print Network [OSTI]

    Cetiner, Bedri A.

    with superior performance over con- ventional semiconductor devices [4]­[7]. Typically, RF MEMS switches-resistivity silicon wafers, gallium arsenide (GaAs) wafers, and quartz substrates using semiconductor Manuscript and surface planarization of wide metal lines prior to deposition of a metal membrane bridge, which poses

  7. 2152 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 17, NO. 11, NOVEMBER 1999 One-Dimensional Photonic Bandgap Microcavities

    E-Print Network [OSTI]

    Fan, Shanhui

    Bandgap Microcavities for Strong Optical Confinement in GaAs and GaAs/Al O Semiconductor Waveguides Daniel been designed, fabricated using high-dielectric-contrast GaAs/AlxOy III­V com- pound semiconductor air-bridge geometries. Resonance states with cavity Q's as high as 360 were measured at wavelengths

  8. Modeling multifrequency eddy current sensor interactions during vertical Bridgman growth of semiconductors

    E-Print Network [OSTI]

    Wadley, Haydn

    Modeling multifrequency eddy current sensor interactions during vertical Bridgman growth methods have been used to analyze the responses of two ``absolute'' and ``differential'' eddy current conductivity ratio increases. Of the materials studied, GaAs is found best suited for eddy current sensing

  9. Amber-green light-emitting diodes using order-disorder Al[subscript x]In[subscript 1?x]P heterostructures

    E-Print Network [OSTI]

    Christian, Theresa M.

    We demonstrate amber-green emission from Al[subscript x]In[subscript 1– x]P light-emitting diodes (LEDs) with luminescence peaked at 566?nm and 600?nm. The LEDs are metamorphically grown on GaAs substrates via a graded ...

  10. JOURNALDE PHYSIQUE IV ColloqueC1, supplCmentau Journal de Physique111,Volume 5,janvier 1995

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    of Technology, FIN-02150 Espoo, Finland Abstract: At a vacant latticecell positron-ion repulsion is reduced. Applications are shown on native vacancies in GaAs. Positrons reveal As and Ga vacanciesin bulk crystals,5]. Around 1980the techniqueof low energy positron beams was developed [6].This opened the avenueof positron

  11. Red emitting photonic devices using InGaP/InGaAlP material system

    E-Print Network [OSTI]

    Kangude, Yamini

    2005-01-01T23:59:59.000Z

    In this thesis, two red emitting photonic devices are presented using the InGaP/InGaAlP material system. InGaP/InGaAlP material system provides large flexibility in the band gap energy while being lattice matched to GaAs ...

  12. IEEE ELECTRON DEVICE LETTERS, VOL. 25, NO. 9, SEPTEMBER 2004 599 Optimized Breakdown Probabilities in

    E-Print Network [OSTI]

    Teich, Malvin C.

    in the GaAs layer. We show theoretically that the same optimized structures yield optimal breakdownAs structure) with the added advantage of having a reduced breakdown voltage (e.g., from 36.5 V to 13.7 V. This work was supported by the National Science Foundation under Awards ECS-0196569 and ECS-0334813. The re

  13. NATIONAL RADIO ASTRONOMY OBSERVATORY GREEN BANK/ WEST VIRGINIA

    E-Print Network [OSTI]

    Groppi, Christopher

    -End Instrumentation Chassis .......... . 4 1. Constant Current Power Supplies for GaAs FET's 4 2. Solid State Relay · · · · ·· · .. ·· ···· ·· · 6 LAB TEST DATA Gain Measurements ........ . ...... -- ····· · ··· 4.· · .0 0... · 7 Noise Tem erature Measurements ..... Impedance Measurements TELESCOPE TEST DATA Gain Measurements Noise Tem erature

  14. Journal of Electronic Materials, Vol. 19, No, 4, 1990 Carbon Tetrachloride Doped AIxGa_xAS

    E-Print Network [OSTI]

    Cunningham, Brian

    Journal of Electronic Materials, Vol. 19, No, 4, 1990 Carbon Tetrachloride Doped AIx been shown to be a suitable carbon doping source for obtaining p-type GaAs grown by metalorganic chemical vapor deposition (MOCVD) with carbon acceptor concentrations in excess of 1 x 1019cm-3

  15. JOURNAL DE PHYSIQUE IV Colloque 3, supplCmentau Journal de Physique 111,Volume 6, avril 1996

    E-Print Network [OSTI]

    Boyer, Edmond

    was in a temperature gradient. The electric contacts were attached to WCs by the method of electric pulse welding Application of Semiconductor Whisker Crystals in Low Temperature Electronics R.I. Baitsar, V.V. Vainberg-Ge and Te-Se solid solutions,Te, 111-Vcompounds (GaAs, Gap, GaAsP) have been studied in a wide temperature

  16. Method for Suppression of Stacking Faults in Wurtzite III-V Nanowires

    E-Print Network [OSTI]

    Heiblum, Mordehai "Moty"

    Method for Suppression of Stacking Faults in Wurtzite III-V Nanowires Hadas Shtrikman,*, Ronit, 2008; Revised Manuscript Received January 13, 2009 ABSTRACT The growth of wurtzite GaAs and In wurtzite structure and are observed to thicken (via lateral growth) once the axial growth exceeds a certain

  17. Limits and accuracy of valence force field models for InxGa1xN alloys Frank Grosse* and Jorg Neugebauer

    E-Print Network [OSTI]

    of the binary zincblende compounds and the formation energy difference to wurtzite are used as input, the model correctly describes the formation energies and structure of wurtzite binary compounds and ternary alloys'' semiconductors like GaAs and, as a consequence, the wurtzite crystal structure. Therefore, a purely elastic model

  18. NON-LINEAR OPTICS IN SEMICONDUCTORS POST DOCTORAL POSITION, PHOTONICS GROUP,

    E-Print Network [OSTI]

    covering most of the infrared region of the spectrum. Harnessing nonlinear interactions is imperative for these devices. In contrast to lithium niobate, compound semiconductors such as GaAs-based compounds exhibit for lithium niobate. GaAs compounds also have high damage threshold and a mature fabrication technology

  19. Department of Electrical Engineering A Novel Refracting Concentration

    E-Print Network [OSTI]

    Su, Xiao

    into electrical energy is solar cell. In past years, solar cells made by Si, GaAs, and matching materials have. Photon Energy E = h = hC/ #12;D. Problem and Challengers · Most state of art solar cells utilizes onlyLili He Department of Electrical Engineering A Novel Refracting Concentration Solar System #12

  20. Growth of InAs Nanowires on SiO2 Substrates: Nucleation, Evolution, and the Role of Au Nanoparticles

    E-Print Network [OSTI]

    Wang, Deli

    particle. The observation of cessation of InAs NW growth at temperatures higher than the "melting)B substrates using selective-area metal organic vapor-phase epitaxy (SA-MOVPE),9 (2) epitaxial substrates through laser ablation of a mixture of GaAs and GaO3,11 and (4) Au-free epitaxial growth of In

  1. The effect of substrates on the Raman spectrum of graphene: Graphene-on-sapphire and graphene-on-glass

    E-Print Network [OSTI]

    The effect of substrates on the Raman spectrum of graphene: Graphene- on-sapphire and graphene The authors investigated the influence of substrates on Raman scattering spectrum from graphene. The room-temperature Raman signatures from graphene layers on GaAs, sapphire, and glass substrates were compared with those

  2. ETSF France Laboratoire des Solides Irradies

    E-Print Network [OSTI]

    Botti, Silvana

    and E. Fiorino and PRB 29 (1984) Third step: calculation of the response functions within time Y. R. Shen PRB (1975) S. Bergfeld and W. Daum, PRL (2003) J. Hugues and J. Sipe,PRB (1996) B. Adolph and F. Bechstedt, PRB (1998) Some results for GaAs Dilation and translation of the energy scale #12

  3. Tilted-mirror semiconductor lasers

    SciTech Connect (OSTI)

    Salzman, J.; Lang, R.; Margalit, S.; Yariv, A.

    1985-07-01T23:59:59.000Z

    Broad-area GaAs heterostructure lasers with a tilted mirror were demonstrated for the first time, with the tilted mirror fabricated by etching. These lasers operate in a smooth and stable single lateral mode with a high degree of spatial coherence. The suppression of filamentation manifests itself in a high degree of reproducibility in the near-field pattern.

  4. Acousto-optical coherence tomography using random phase jumps on

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    (cm). Up to now, several configurations have been studied, giving a millimetric axial resolution demonstration is performed with a self-adaptive holographic setup containing a photorefractive GaAs bulk crystal(5), 1151­1158 (1997). 4. S. Leveque, A. C. Boccara, M. Lebec, and H. Saint-Jalmes, "Ultrasonic tagging

  5. JOURNAL DE PHYSIQUE Colloque CIO, suppliment au n012, Tome 44, dkembre 1983 page ClO-39

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    exigeant que no, et dox restent inchangks. Les rksultats obtenus pour GaAs et InP sont prgsentks. Abstract oxide (nox, kox, dox) from the values of $M and AM is done using the Fresnel-Drude formulae. This method

  6. Thermodynamics, Entropy, Information and the Efficiency of Solar Cells

    E-Print Network [OSTI]

    Abrams, Zeev R.

    2012-01-01T23:59:59.000Z

    CIGS, so the addition of the dc layer would not alter the material choice for a solar cell.solar cell, the use of GaAs has recently become feasible due to scalable manufacturing techniques, and compound materials such as CIGS (

  7. High-frequency microstrip cross resonators for circular polarization electron paramagnetic resonance spectroscopy

    E-Print Network [OSTI]

    del Barco, Enrique

    resonators, designed to match the 50 impedance of the lines on a high dielectric constant GaAs substrate excitation at the center of the cross resonator. The third output port is used to measure the transmitted resonator, composed of two half- wavelength microstrip line resonators which allow an in situ and all

  8. A Resistive-Gate InAlAs/InGaAs/InP2DEG CCD D.V. Rossi, A.-N. Chengl, H.H. Wiederl, and E.R. Fossurn2

    E-Print Network [OSTI]

    Fossum, Eric R.

    GaAs cap layer and recess of the InAlAs layer was performed using the AuGeNi contacts as a mask and H2S04:H thermal annealing at 4OO0C for 15 sec under a forming gas ambient, and the subsequent removal of the In

  9. A 24-GHZ ACTIVE PATCH ARRAY Dai Lu, Milan Kovacevic, Jon Hacker and David Rutledge

    E-Print Network [OSTI]

    proved a 12-dB antenna gain. A power amplifier and a low noise amplifier are designed on a single Ga noise amplifier applications, more recently GaAs PHEMTs have found applications in the low to medium amplifier and low noise amplifier are designed at 24 GHz. While the T/R switch loss is greatly reduced

  10. Applications of Self-assembly for Molecular Electronics, Plasmon Coupling, and Ion Sensing 

    E-Print Network [OSTI]

    Chan, Yang-Hsiang

    2011-08-08T23:59:59.000Z

    of a simple platform to examine the coupling between metal nanostructures and quantum dot assemblies. Here we demonstrate that by using a patterned array of Au or Ag nanoparticles on GaAs, plasmon enhanced photoluminescence (PL) can be directly measured...

  11. JOURNALDE PHYSIQUE IV ColloqueC6 Suppltmentau Journal de Physique ID, Volume 4,juin 1994

    E-Print Network [OSTI]

    Boyer, Edmond

    oscillator based on a GaAs HEMT integrated to a HTS resonator G. Borghs, J. DeBoeck, I. Francois, D a superconductingresonator patterned on a MgO substrate, a gold matching network fabricated on A1203 and a transistor wire or communications are likely to be the first area of practical applications of high temperature superconductors (HTS

  12. EE Times: Semi News Groups claim breakthroughs in solar cells

    E-Print Network [OSTI]

    Rogers, John A.

    -based, multi-junction solar cells. Module cost is minimized by using high concentration ratio. XEE Times: Semi News Groups claim breakthroughs in solar cells Mark LaPedus Page 1 of 2 EE Times (05 separately claimed breakthroughs in solar cell production. Gallium arsenide (GaAs) and related compounds

  13. Quasi-Rheotaxy a new technique to grow large grain thin films on low cost amorphous substrates (*)

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    , could be used to build low cost thin film solar cells. Revue Phys. Appl. 16 (1981) 11-14 JANVIER 1981 is required in thin film direct gap absorbers solar cells to overcome thebfficiency value of 10 % is about 2 comparable with the grain size, reports that a thin film solar cell based on GaAs with a resistivity of 10

  14. Optical, electrical, and solar energy-conversion properties of gallium arsenide nanowire-array

    E-Print Network [OSTI]

    Zhou, Chongwu

    Optical, electrical, and solar energy-conversion properties of gallium arsenide nanowire, and will aid in the design and optimization of nanowire-based systems for solar energy-conversion applications, and the photoelectrochemical energy-conversion properties of GaAs nanowire arrays were evaluated in contact with one

  15. New Technique for Molecular-Dynamics Computer-Simulations - Hellmann-Feynman Theorem and Subspace Hamiltonian Approach

    E-Print Network [OSTI]

    MENON, M.; Allen, Roland E.

    1986-01-01T23:59:59.000Z

    of the GaAs surface. The z coordinate is positive above the surface. We use the following "natural" units: length, 1 A; force, 1 eV/A; time, 5.3X 10 'z sec; and velocity, 1.9X10 m/sec. For all of the results shown below, we ~mp the motion...

  16. GLAS-PPE/2002-16 Department of Physics & Astronomy

    E-Print Network [OSTI]

    Glasgow, University of

    ratio) in semiconductor material here was laser drilling. The main advantages of using a laser is that it is independent of the material drilled (e.g. silicon, gallium arsenide, silicon carbide and CdZnTe) and it is the best technique available currently for GaAs. The drilling operation was carried out at Strathclyde

  17. IEEE ELECTRON DEVICE LETTERS. VOL. EDL-6, NO. 10, OCTOBER 1985 491 J. J. ROSENBERG, M. BENLAMRI, P. D. KIRCHNER, J. M. WOODALL, AND G. D. PETTIT

    E-Print Network [OSTI]

    Woodall, Jerry M.

    IEEE ELECTRON DEVICE LETTERS. VOL. EDL-6, NO. 10, OCTOBER 1985 491 J. J. ROSENBERG, M. BENLAMRI, P of the reported heterojunction FET devices utilize A1,Gal _,As/ GaAs heterojunctions in which electrons. D. KIRCHNER, J. M. WOODALL, AND G. D. PETTIT Abstract-This letter describes high electron mobility

  18. Guided self-assembly of Au nanocluster arrays electronically coupled to semiconductor device layers

    E-Print Network [OSTI]

    Woodall, Jerry M.

    Guided self-assembly of Au nanocluster arrays electronically coupled to semiconductor device layers clusters within patterned regions on GaAs device layers, thus demonstrating guided self-assembly on a substrate which can provide interesting semiconductor device characteristics. Uniform nanometer scale

  19. LED Light Sources for Projection Display Applications

    E-Print Network [OSTI]

    Palffy-Muhoray, Peter

    LED Light Sources for Projection Display Applications By Chenhui Peng 04-13-2012 #12;Outline · 1. · The first practical LED is in red color and it is made with gallium arsenide (GaAs). 4http://en.wikipedia.org/wiki/Light with holes and release energy in the form of photons. 5http://en.wikipedia.org/wiki/Light-emitting_diode #12

  20. GaGa11--xxMnMnxxAsAs11--yyTeTeyy Synthesized bySynthesized by Ion Implantation & Pulsed Laser MeltingIon Implantation & Pulsed Laser Melting

    E-Print Network [OSTI]

    Priour, Don - Department of Physics, University of Missouri

    ] · stabilizing EF by compensation might allow higher MnGa add Te · experiment possible using II-PLM no chamber Implantation & Pulsed Laser Melting (IIPulsed Laser Melting (II--PLM)PLM) Excimer Laser Pulse GaAs Liquid Melt, NATURE MATERIALS 1 185 (2002) [4] Scarpulla, PHYSICA B 340 908 (2003) #12;IIII--PLM GaPLM Ga11--xx

  1. Highly Mismatched Semiconductor Alloys with Extreme Compositions

    E-Print Network [OSTI]

    Levander, Alejandro X.

    2012-01-01T23:59:59.000Z

    mol% n n N N N N As N I ? D PLM PLA PR q r r R e r-space RBSN whereas an optimized PLM treatment results in ~0.8 mol%N incorporated into GaAs from a PLM or RTA process. As the

  2. Charge Hall effect driven by spin-dependent chemical potential gradients and Onsager relations in mesoscopic systems RID B-8398-2011 RID A-7392-2009

    E-Print Network [OSTI]

    Hankiewicz, EM; Li, J.; Jungwirth, T.; Niu, Q.; Shen, SQ; Sinova, Jairo.

    2005-01-01T23:59:59.000Z

    -current response generated perpendicular to the driving electric field. Recently, the spin Hall effect was experimentally ob- served by Kato et al.6 in n-doped GaAs using the Kerr effect and by Wunderlich et al.7 in the p-n junction light-emitting diodes based...

  3. Midinfrared scattering and absorption in Ge powder close to the Anderson localization transition J. Gomez Rivas, R. Sprik, and A. Lagendijk

    E-Print Network [OSTI]

    Sprik, Rudolf

    localization (kls 1) of near infrared light was reported in GaAs (n 3.5) powder samples consisting of randomly a free electron laser we have performed midinfrared transmission and reflection measurements in strongly transition. The refractive index of Ge is very high in the near and midinfrared (n 4.0) 8

  4. Suppression of the thermal hysteresis in magnetocaloric MnAs thin film by highly charged ion bombardment

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    temperature opening new perspective on magnetic refrigeration technology for everyday use. martino on the modifications of structural and magnetic properties of MnAs thin film epitaxially grown on GaAs induced by slow and magnetic prop- erties. In particular, the irradiated film keeps the giant magnetocaloric effect at room

  5. Harry Atwater is the Howard Hughes Professor of Applied Physics and Materials Science at the California

    E-Print Network [OSTI]

    Faraon, Andrei

    efficiency/low cost GaAs photovoltaics technology, and of Caelux Corporation, a venture-backed photovoltaics interests have two themes: photovoltaics and solar energy as well as plasmonics and optical metamaterials. His group has created new high efficiency solar cell designs, and have developed principles for light

  6. Plasmonic Nanostructure Design for Efficient Light Coupling into Solar Cells

    E-Print Network [OSTI]

    Atwater, Harry

    Plasmonic Nanostructure Design for Efficient Light Coupling into Solar Cells Vivian E. Ferry, Luke sunlight into guided modes in thin film Si and GaAs plasmonic solar cells whose back interface is coated. These findings show promise for the design of ultrathin solar cells that exhibit enhanced absorption

  7. IBM Systems and Technology IBM SiGe 5PAe and

    E-Print Network [OSTI]

    IBM Systems and Technology IBM SiGe 5PAe and 1KW5PAe technologies Keep pace with mobile advances SiGe offerings featuring copper pillar and through-silicon-via options Take advantage of ongoing to solutions based on gallium arsenide (GaAs) technology, for example, the IBM SiGe 5PAe family offers several

  8. 118 IEEE ELECTRON DEVICE LETTERS, VOL. 19, NO. 4, APRIL 1998 Submicron Self-Aligned HBT's

    E-Print Network [OSTI]

    Asbeck, Peter M.

    are made up of a special three-layer stack: p-GaAs/p-InGaP/ -GaAs (1500/500/500 °A) doped to Manuscript growth along the sidewall with no gaps or voids. A 1000 °A n-InGaP layer doped at cm was used as the wide

  9. Laser cooling of a semiconductor load to 165 K Denis V. Seletskiy1,*

    E-Print Network [OSTI]

    Sheik-Bahae, Mansoor

    : We demonstrate cooling of a 2 micron thick GaAs/InGaP double- heterostructure to 165 K from ambient efficiency in GaAs/ InGaP double heterostructures for laser cooling applications," Proc. SPIE 7614, 76140B

  10. FIGURE 1. (a) Side view schematic of the integrated short-cavity DBR laser-modulator, illustrating the Gain, DBR, and EAM sections. (b) Epitaxial base structure. To the right illustrates the intermixing process used: (i) surface fluorination followed by S

    E-Print Network [OSTI]

    Coldren, Larry A.

    , as shown in Fig. 1b. The upper waveguide also includes a GaAs regrowth layer followed by a sacrificial InGaP the active band-edge. Following QWI, the sacrificial InGaP layer is removed, and first order gratings

  11. Operating Characteristics of GaAs/InGaP Self Aligned Stripe Lasers Benjamin J. Stevens1

    E-Print Network [OSTI]

    Operating Characteristics of GaAs/InGaP Self Aligned Stripe Lasers Benjamin J. Stevens1 , Kristian of GaAs based self-aligned lasers based upon a single overgrowth. A lattice matched n-doped InGaP layer were exposed to oxygen. True buried heterostructures devices utilising InGaP clad- ding layers have

  12. Ferromagnetic semiconductors based upon AlGaP M. E. Overberg,a)

    E-Print Network [OSTI]

    Hebard, Arthur F.

    band-gap ternary InGaP, which is lattice matched to GaAs. An immediate application of the DMS, with its wide band-gap binary GaP, AlP and ternary InGaP, AlGaP, AlInP components, is used for devices

  13. Local far-infrared spectroscopy of edge states in the quantum Hall regime A. Lorke* and J. P. Kotthaus

    E-Print Network [OSTI]

    Ludwig-Maximilians-Universität, München

    resolution well below typical Hall bar dimensions,7,8 the other is the use of the edge channels them- selves are as follows: Buffer and smoothing layers, 1 m GaAs, a 15-nm AlxGa1 xAs (x 0.3) spacer layer, 3.9 1012 - cm 2

  14. Edge magnetoplasmons in single two-dimensional electron disks at microwave frequencies: Determination of the lateral depletion length

    E-Print Network [OSTI]

    Ludwig-Maximilians-Universität, München

    differs from the 3D case because of the particular screening proper- ties in lower dimensions. In devices, a 200-Ã?-thick AlxGa1 xAs spacer layer, a 400 Ã? Si-doped AlxGa1 xAs layer, and a 200 Ã? GaAs cap layer

  15. Criteria for One-Dimensional Transport in Split-Gate Field-Effect Transistors Cristopher C. Eugster, JesGs A. del Alamo, Paul A. Belk and Michael J. Rooks'

    E-Print Network [OSTI]

    del Alamo, Jesús A.

    miniaturization of today's electronic devices will soon lead to devices with dimensions comparable to the electron" cm-$, a 7.5 nm undoped AlGaAs spacer, and a 1 pm GaAs buffer. The mobility of the 2D elec- tron gas

  16. An overview of quantumquantum dotdot synthesis, applications

    E-Print Network [OSTI]

    S III-V: GaAs, GaN, InP, InAs, InGaAs IV-VI: PbS, PbSe II IV V VIIII #12;What do Quantum Dots look like;Luminescence Energy Ground State Excited State Absorption (excitation) Fluorescence (emission) #12

  17. The Molecular Foundry User Proposal Form Proposal: MELOSH_05-04-2009_16-09-29

    E-Print Network [OSTI]

    Lee, Jason R.

    : Monday, May 04, 2009 Photoemission of GaN and GaAs nanowires. Project Leader: Name: Prof. Nickolas Melosh. This is a Sample Only proposal. This proposal is not a follow on proposal. In previous photoemission tests GaN or electron emission. We would like to investigate the photoemissive properties of p-type and n-type GaN

  18. www.advmat.de www.MaterialsViews.com

    E-Print Network [OSTI]

    Xiong, Qihua

    based on group IV elements (Si and Ge),[4] III­V compound semiconduc- tors (GaN and GaAs),[2), good absorption ability, and excellent photosensi- tivity,[8,9] CdSe is recognized as a promising light investigated systematically by measurements of optical absorption and photoluminescence (PL) down to 10 K. We

  19. Terahertz dielectric properties of high-resistivity single-crystal ZnO Abul K. Azad

    E-Print Network [OSTI]

    experimentally that ZnO shows significantly higher radiation hardness than Si, GaN, and GaAs.5 Additionally absorption, and dielectric function are well fit by the pseudo-harmonic model of dielectric response. In addition, from the extrapolation of the experimental results, we show that the absorption is dominated

  20. Vertical strain and doping gradients in thick GaN layers H. Siegle,a)

    E-Print Network [OSTI]

    Nabben, Reinhard

    between layer and common substrates, e.g., sapphire or GaAs.1 Consequently, most GaN layers and also from the surface of the GaN layer nearer to the substrate interface, as can be seen from the CLVertical strain and doping gradients in thick GaN layers H. Siegle,a) A. Hoffmann, L. Eckey, and C

  1. NCRC, The University of Tokyo Yasuhiko Arakawa

    E-Print Network [OSTI]

    .5µm0.5µm 1.0µm 1.5µm Visible Near Infrared InP Substrate GaN GaAs For optical communication system/biexciton to single photon/ entangled photon · Single photon sources · Growth and optical properties of GaN quantum

  2. Spatiotemporal shaping of half-cycle terahertz pulses by diffraction through

    E-Print Network [OSTI]

    Stroud, Carlos R.

    demonstrate a simple quasi-optical technique for spatiotemporal shaping of half-cycle terahertz-radiation (such as GaAs, InP, or CdTe) or radiation-damaged silicon-on-sapphire. Generated carri- ers are rapidly of finite thickness Jake Bromage, Stojan Radic, G. P. Agrawal, and C. R. Stroud, Jr. The Institute of Optics

  3. DOI: 10.1007/s00339-003-2405-0 Appl. Phys. A 78, 465469 (2004)

    E-Print Network [OSTI]

    -GaAs) or radiation-damaged Si on sapphire, that are time gated by a synchronised probe pulse [4, 10]. Electro- optic-infrared or terahertz (1 THz = 1012 Hz) radiation is that it can easily penetrate ob- jects that are opaque to visible, THz radiation has the advantage that it is non- ionising, because a THz photon has an extremely small

  4. Structural Studies of Potential 1 eV Solar Cell Materials

    SciTech Connect (OSTI)

    Norman, A.; Al-Jassim, M.; Friedman, D.; Geisz, J.; Olson, J.; Kurtz, S.

    2000-01-01T23:59:59.000Z

    Structural studies using transmission electron microscopy have been made on 1-eV band-gap materials, lattice-matched to GaAs and Ge substrates, grown by metal-organic vapor-phase epitaxy for use in multijunction, high-efficiency solar cells.

  5. Role of Ion Damage on Unintentional Ca Incorporation During the Plasma-Assisted Molecular-Beam Epitaxy Growth of Dilute Nitrides Using N2/Ar Source Gas Mixtures

    SciTech Connect (OSTI)

    Oye, M. M.; Bank, S. R.; Ptak, A. J.; Reedy, R. C.; Goorsky, M. S.; Holmes Jr., A. L.

    2008-05-01T23:59:59.000Z

    Unintentional Ca incorporation caused by Ca-contaminated substrate surfaces on as-purchased GaAs wafers are known to limit the efficiency of solar cells based on dilute nitride materials. This article focuses on further understanding the conditions and mechanisms by which these Ca impurities incorporate. Plasma-assisted molecular-beam epitaxy utilizing a 1% N{sub 2} in Ar precursor gas mixture was used to grow GaAs at 400 and 580 C, and GaN{sub 0.01}As{sub 0.99} at 400 C. Two plasma operating combinations of rf power and gas flow rate were used to generate different amounts and energies of both ions and other plasma species, while keeping nitrogen incorporation constant. The ions were characterized with a dual-grid, retarding-field ion energy analyzer, and the corresponding ion energy distributions are presented to correlate ions with Ca incorporation. When appropriate, dc-biased deflector plates were used to remove ions during growth. Secondary ion mass spectrometry was used to measure Ca in GaAs and GaN{sub 0.01}As{sub 0.99}. Ca incorporation was observed in the dilute nitride samples, but the effects of ions did not exceed other Ca incorporation mechanisms associated with defects due to both low temperature growth and nitrogen incorporation; however, different neutral active nitrogen species (atomic N and metastable N{sub 2}) may be a factor. Ca incorporation measured in GaAs grown at 400 C with a pure Ar plasma is predominantly due to defects associated with low temperature growth, as opposed to plasma damage caused by the ions. GaAs growths at 580 C without a plasma did not exhibit Ca incorporation, but growth at 580 C with ions from a pure Ar plasma caused Ca incorporation.

  6. Thin films of gallium arsenide on low-cost substrates. Final technical report, July 5, 1976-December 5, 1978

    SciTech Connect (OSTI)

    Ruth, R.P.; Dapkus, P.D.; Dupuis, R.D.; Johnson, R.E.; Moudy, L.A.; Yang, J.J.; Yingling, R.D.

    1980-03-01T23:59:59.000Z

    The MO-CVD technique was applied to the growth of thin films of GaAs and GaAl As on inexpensive polycrystalline or amorphous substrate materials (primarily glasses and metals) for use in fabrication of large-area low-cost photovoltaic device structures. Trimethylgallium, arsine, and trimethylaluminum are mixed in appropriate concentrations at room temperature in the gaseous state and pyrolyzed at the substrate, which is heated in a vertical reactor chamber to temperatures of 700 to 750/sup 0/C, to produce the desired film composition and properties. Studies of the properties of grain boundaries in polycrystalline GaAs films by the use of transport measurements as a function of temperature indicated that the grain boundary regions are depleted of majority carriers by a large density of neutral traps at the grain boundary interface, causing a barrier to majority carrier flow in the material. Schottky-barrier solar cells of approx. 3 percent efficiency (simulated AM0 illumination, no AR coating) were demonstrated on thin-film polycrystalline GaAs n/n/sup +/ structures on Mo sheet, Mo film/glass, and graphite substrates. Substantial enhancement of average grain size in polycrystalline MO-CVD GaAs films on Mo sheet was obtained by the addition of HCl to the growth atmosphere during deposition. Extensive investigation of polycrystalline thin-film p-n junctions indicated that the forward voltage of such devices is apparently limited to 0.5 to 0.6V. A laboratory-type deposition apparatus for the formation of TiO/sub 2/ antireflection (AR) coatings by pyrolysis of titanium isopropoxide was assembled and tested. Detailed analyses were made of the materials and labor costs involved in the laboratory-scale fabrication of MO-CVD thin-film GaAs solar cells. Details are presented. (WHK)

  7. Holocene Salnia sediments of West Caicos, British West Indies: stratigraphy, mineralogy, and pore-water geochemistry

    SciTech Connect (OSTI)

    Rosoff, D.B.; Dwyer, G.S.; Leaver, J.; Perkins, R.D.; Lloyd, R.M.

    1989-03-01T23:59:59.000Z

    A study of east Salina on West Caicos, British West Indies, has shown it to be the site of active gypsum and dolomite formation. East salina, 3 km long and 0.25 km wide, is situated in an elongate depression between Holocene oolitic dunes to the east and eolianite ridges of Pleistocene age to the west. The thickness of the Holocene sediment package in the salina ranges from 3 m in the center to less than 0.5 m at the edges. The salina sediments exhibit an overall restrictive-upward sequence which grades from open-marine packstone and grainstone at the base through algally laminated mud and into a gypsum mush in the uppermost part of the section. A thin algal mat encrusted with gypsum and ephemeral halite covers the salina surface. This sequence is virtually identical in scale and appearance to prograding sabkha sequences reported from the Persian Gulf. Carbonate phases present in these sediments include aragonite, high- and low-magnesium calcite, and protodolomite. Protodolomite is found as an alteration product in the open-marine sediments and within a thin, lithified Holocene basal layer that overlies laminated calichecrust on the underlying Pleistocene bed rock. Analyses of pore waters reveal that they approach normal marine salinity at the base of the salina sequence and become hypersaline upward. Mineralogical changes in the salina sequence are reflected in the ionic character of the pore waters. Field observations indicate that interstitial water within the sequence is under hydraulic head and rises and falls with the tides.

  8. ACAA 2006 fall meeting

    SciTech Connect (OSTI)

    NONE

    2006-07-01T23:59:59.000Z

    The seven presentations (in pdf format) on the CD-ROM are: Amended Silicates{trademark}: mercury control without harming fly ash (J. Butz and others); benefits of gypsum in agriculture (L.D. Norton); co-firing biomass in pc fired units (C. Meijer and others); minimizing the impact of air pollution control equipment retrofits on saleability of fly ash (C.Weilert); new power plant construction - CCP readiness (T. Jansen); recent utilization of fly ash in coal plant construction (J. Liljegren and T. Hart); and resource conservation challenge (C. McLaughlin).

  9. A field evaluation of the movement of selected metals in revegetated strip mine overburden and laboratory assessment of transport mechanisms

    E-Print Network [OSTI]

    Launius, Kenneth Wayne

    1980-01-01T23:59:59.000Z

    placement of materials following the excavation and sampling of lignite at a test pit. The effect of varying ratios of lime and gypsum had on revegetation were studied. Resultant overburden'pH and electrical conductivity (EC) wire evaluated... are needed to ach1eve energy self sufficiency for the Un1ted States. Advanced technology is needed to economically harness the cleanest source of alternate energy, the sun. However, another source of energy available us1ng present-day technology is coal...

  10. Irrigation-suitability land classification of the Rechna Doab in Pakistan

    E-Print Network [OSTI]

    Rehman, Gauhar

    1987-01-01T23:59:59.000Z

    . So the practice of providing only additional water f?r reclamati&m is wasting precious irrigation resources. Low salinity level requires very little water for h aching and the soil vrould improve by application of gypsum. Reclamation Programs...&&n in irrigation and soil water (as propos&. d by Ifhoades, (19i2)), has b&. en included in the models constraint set. The use of this model facilitates planning deci- sions like quantities and locations of all resource inputs, mixing ratios bet&veen different...

  11. Managing Soil Salinity 

    E-Print Network [OSTI]

    Provin, Tony; Pitt, John L.

    2001-07-13T23:59:59.000Z

    both surface water and groundwater often are a combina- tion of sodium, calcium, potassium, magnesium, chlo- rides, nitrates, sulfates, bicarbonates and carbonates (Table 1). These salts often originate from the earth?s crust. They also can result from... Magnesium sulfate MgSO 4 Gypsum Calcium sulfate CaSO 4 2H 2 O Street salt Calcium chloride CaCl 2 2H 2 O Muriate of potash Potassium chloride KCl Muriate of sulfate Potassium sulfate K2SO 4 seen. Fortunately, plants take up many salts in the form...

  12. Oxidation kinetics of by-product calcium sulfite 

    E-Print Network [OSTI]

    Othman, Hasliza

    1992-01-01T23:59:59.000Z

    by hydration to dihydrate. Another low energy technique under study is to develop a sulfate resistant cement which does not react with dihydrate to form deleterious expansive compounds. One of the paramount requirements necessary for utilizing... calcium sulfite hemihydrate. Ca + SO2 + 2H20 ? -& CaSO2. 2H20 (s) 2+ 2- 1 Due to the presence of excess air in the system, some sulfite is oxidized to sulfate and precipitates as calcium sulfate dihydrate (gypsum). SO2 + &O2 ? &804 2 1 2- Ca + SO4...

  13. 'The Overriding Demand for Energy Conservation in the Cement Industry' An Update

    E-Print Network [OSTI]

    Spellman, L. U.

    1981-01-01T23:59:59.000Z

    addi tives. While cement makes up only about 7 to 15 percent of the weight of concrete, it is 1:5y far the greatest contributor of energy content in the mixture. Cement, usually portland cement, is a product derived from pyro-processing calcareous... and argillaceous materials such as limestone and clay or shale into an intermediate fused material called clinker, which is subse quently ground together with a small amount of gypsum. Portland cement is the principal material produced by the U. S. cement...

  14. Neutron Spectrometry for Identification of filler material in UXO - Final Report

    SciTech Connect (OSTI)

    Bliss, Mary

    2007-09-12T23:59:59.000Z

    Unexploded ordnance (UXO)-contaminated sites often include ordnance filled with inert substances that were used in dummy rounds. During UXO surveys, it is difficult to determine whether ordnance is filled with explosives or inert material (e.g., concrete, plaster-of-paris, wax, etc.) or is empty. Without verification of the filler material, handling procedures often necessitate that the object be blown in place, which has potential impacts to the environment, personnel, communities and survey costs. The Department of Defense (DoD) needs a reliable, timely, non-intrusive and cost-effective way to identify filler material before a removal action. A new technology that serves this purpose would minimize environmental impacts, personnel safety risks and removal costs; and, thus, would be especially beneficial to remediation activities.

  15. Generation of graphitic soots by an urban fire storm

    SciTech Connect (OSTI)

    Fields, D.E.; Cole, L.L.

    1987-01-01T23:59:59.000Z

    We have obtained samples of aerosols deposited during the Hiroshima fire storm that was initiated by the atomic bomb detonated on August 6, 1945, from streaks of ''black rain'' found on a plaster wall. The artifact appears to contain aerosol particles that may be representative of the aerosols that may lead to a ''nuclear winter'' (Turco 1983). Gamma spectroscopy measurements indicate the presence of naturally-occurring radionuclides K-40, Ra-226, Ra-228, Th-232, and Th-234, along with the fission product, Cs-137. Sooty particles of varying sizes have been detected using optical photomicrography and examined using x-ray induced x-ray fluorescence. The elements Ca, Sr, Ba, Fe, and Zn, have been detected, and exhibit elemental composition ratios representative of Hiroshima soil. Particle composition and size studies indicate that the particle sizes have a mean diameter of 1.8 microns, and that 30% are less than 1 micron in mean diameter.

  16. Economics of gobar gas

    SciTech Connect (OSTI)

    Pang, A.; Shrestha, P.C.; Fulford, D.

    1980-01-01T23:59:59.000Z

    This series of reports follows a sequence necessary to start and run a biogas project. The first provides and introduction to biogas, its costs, and its yields. Its use will conserve forests, create clean, healthy fuel and fertilizer, and save Nepal foreign exchange. The feasibility study considered water and dung supply, degree of cooperation among the affected villagers, the need for the plant, and intangibles such as erosion control. The initial survey investigates the community social situation, needs, and cooperation. The Gobar Gas company had had personnel problems which decreased service, but the problems were being worked out. The project has been highly successful. The 11 Chinese plants worked well with no leaks from the cement but the gas valves leaked. The scum breaker also caused problems. The high quality plaster work required is the greatest hindrance.

  17. ENGINEERING A NEW MATERIAL FOR HOT GAS CLEANUP

    SciTech Connect (OSTI)

    T.D. Wheelock; L.K. Doraiswamy; K. Constant

    2001-06-30T23:59:59.000Z

    The overall objective of this project is the engineering development of a reusable calcium-based sorbent for desulfurizing hot coal gas. A two-step pelletization method has been employed to produce relatively strong, ''core-in-shell,'' spherical pellets. Each pellet consists of a highly reactive core surrounded by a strong, inert, porous shell. A suitable core is composed largely of CaO which reacts with H{sub 2}S to form CaS. Pellet cores have been prepared by pelletizing either pulverized limestone or plaster of Paris, and shells have been made of various materials. The most suitable shell material has been formed from a mixture of alumina and limestone particles. The core-in-shell pellets require treatment at high temperature to convert the core material to CaO and to partially sinter the shell material. Pellet cores derived from plaster of Paris have proved superior to those derived from limestone because they react more rapidly with H{sub 2}S and their reactivity does not seem to decline with repeated loading and regeneration. The rate of reaction of H{sub 2}S with CaO derived from either material is directly proportional to H{sub 2}S concentration. The rate of reaction does not appear to be affected significantly by temperature in the range of 1113 K (840 C) to 1193 K (920 C) but decreases markedly at 1233 K (960 C). The rate is not affected by shell thickness within the range tested, which also provides adequate compressive strength.

  18. Shallow groundwater and soil chemistry response to 3 years of subsurface drip irrigation using coalbed-methane-produced water

    SciTech Connect (OSTI)

    Bern, C. R.; Boehlke, A. R.; Engle, M. A.; Geboy, N. J.; Schroeder, K. T.; Zupancic, J. W.

    2013-12-01T23:59:59.000Z

    Disposal of produced waters, pumped to the surface as part of coalbed methane (CBM) development, is a significant environmental issue in the Wyoming portion of the Powder River Basin, USA. High sodium adsorption ratios (SAR) of the waters could degrade agricultural land, especially if directly applied to the soil surface. One method of disposing of CBM water, while deriving beneficial use, is subsurface drip irrigation (SDI), where acidified CBM waters are applied to alfalfa fields year-round via tubing buried 0.92 m deep. Effects of the method were studied on an alluvial terrace with a relatively shallow depth to water table (?3 m). Excess irrigation water caused the water table to rise, even temporarily reaching the depth of drip tubing. The rise corresponded to increased salinity in some monitoring wells. Three factors appeared to drive increased groundwater salinity: (1) CBM solutes, concentrated by evapotranspiration; (2) gypsum dissolution, apparently enhanced by cation exchange; and (3) dissolution of native Na–Mg–SO{sub 4} salts more soluble than gypsum. Irrigation with high SAR (?24) water has increased soil saturated paste SAR up to 15 near the drip tubing. Importantly though, little change in SAR has occurred at the surface.

  19. Multiphase flow and multicomponent reactive transport model of the ventilation experiment in Opalinus clay

    SciTech Connect (OSTI)

    Zheng, L.; Samper, J.; Montenegro, L.; Major, J.C.

    2008-10-15T23:59:59.000Z

    During the construction and operational phases of a high-level radioactive waste (HLW) repository constructed in a clay formation, ventilation of underground drifts will cause desaturation and oxidation of the rock. The Ventilation Experiment (VE) was performed in a 1.3 m diameter unlined horizontal microtunnel on Opalinus clay at Mont Terri underground research laboratory in Switzerland to evaluate the impact of desaturation on rock properties. A multiphase flow and reactive transport model of VE is presented here. The model accounts for liquid, vapor and air flow, evaporation/condensation and multicomponent reactive solute transport with kinetic dissolution of pyrite and siderite and local-equilibrium dissolution/precipitation of calcite, ferrihydrite, dolomite, gypsum and quartz. Model results reproduce measured vapor flow, liquid pressure and hydrochemical data and capture the trends of measured relative humidities, although such data are slightly overestimated near the rock interface due to uncertainties in the turbulence factor. Rock desaturation allows oxygen to diffuse into the rock and triggers pyrite oxidation, dissolution of calcite and siderite, precipitation of ferrihydrite, dolomite and gypsum and cation exchange. pH in the unsaturated rock varies from 7.8 to 8 and is buffered by calcite. Computed changes in the porosity and the permeability of Opalinus clay in the unsaturated zone caused by oxidation and mineral dissolution/precipitation are smaller than 5%. Therefore, rock properties are not expected to be affected significantly by ventilation of underground drifts during construction and operational phases of a HLW repository in clay.

  20. In-situ early-age hydration study of sulfobelite cements by synchrotron powder diffraction

    SciTech Connect (OSTI)

    Álvarez-Pinazo, G.; Cuesta, A.; García-Maté, M.; Santacruz, I.; Losilla, E.R. [Departamento de Química Inorgánica, Universidad de Málaga, Campus Teatinos S/N., 29071 Málaga (Spain)] [Departamento de Química Inorgánica, Universidad de Málaga, Campus Teatinos S/N., 29071 Málaga (Spain); Sanfélix, S.G. [Unidad Técnica de Investigación de Materiales, AIDICO, Avda. Benjamín Franklin, 17 Paterna, Valencia (Spain)] [Unidad Técnica de Investigación de Materiales, AIDICO, Avda. Benjamín Franklin, 17 Paterna, Valencia (Spain); Fauth, F. [CELLS-Alba synchrotron, Carretera BP 1413, Km. 3.3, E-08290 Cerdanyola, Barcelona (Spain)] [CELLS-Alba synchrotron, Carretera BP 1413, Km. 3.3, E-08290 Cerdanyola, Barcelona (Spain); Aranda, M.A.G. [Departamento de Química Inorgánica, Universidad de Málaga, Campus Teatinos S/N., 29071 Málaga (Spain) [Departamento de Química Inorgánica, Universidad de Málaga, Campus Teatinos S/N., 29071 Málaga (Spain); CELLS-Alba synchrotron, Carretera BP 1413, Km. 3.3, E-08290 Cerdanyola, Barcelona (Spain); De la Torre, A.G., E-mail: mgd@uma.es [Departamento de Química Inorgánica, Universidad de Málaga, Campus Teatinos S/N., 29071 Málaga (Spain)

    2014-02-15T23:59:59.000Z

    Eco-friendly belite calcium sulfoaluminate (BCSA) cement hydration behavior is not yet well understood. Here, we report an in-situ synchrotron X-ray powder diffraction study for the first hours of hydration of BCSA cements. Rietveld quantitative phase analysis has been used to establish the degree of reaction (?). The hydration of a mixture of ye'elimite and gypsum revealed that ettringite formation (? ? 70% at 50 h) is limited by ye'elimite dissolution. Two laboratory-prepared BCSA cements were also studied: non-active-BCSA and active-BCSA cements, with ?- and ??{sub H}-belite as main phases, respectively. Ye'elimite, in the non-active-BCSA system, dissolves at higher pace (? ? 25% at 1 h) than in the active-BCSA one (? ? 10% at 1 h), with differences in the crystallization of ettringite (? ? 30% and ? ? 5%, respectively). This behavior has strongly affected subsequent belite and ferrite reactivities, yielding stratlingite and other layered phases in non-active-BCSA. The dissolution and crystallization processes are reported and discussed in detail. -- Highlights: •Belite calcium sulfoaluminate cements early hydration mechanism has been determined. •Belite hydration strongly depends on availability of aluminum hydroxide. •Orthorhombic ye’elimite dissolved at a higher pace than cubic one. •Ye’elimite larger reaction degree yields stratlingite formation by belite reaction. •Rietveld method quantified gypsum, anhydrite and bassanite dissolution rates.

  1. Composite materials for thermal energy storage

    DOE Patents [OSTI]

    Benson, D.K.; Burrows, R.W.; Shinton, Y.D.

    1985-01-04T23:59:59.000Z

    A composite material for thermal energy storage based upon polyhydric alcohols, such as pentaerythritol, trimethylol ethane (also known as pentaglycerine), neopentyl glycol and related compounds including trimethylol propane, monoaminopentaerythritol, diamino-pentaerythritol and tris(hydroxymethyl)acetic acid, separately or in combinations, which provide reversible heat storage through crystalline phase transformations. These PCM's do not become liquid during use and are in contact with at least one material selected from the group consisting of metals, carbon, siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, porous rock, and mixtures thereof. Particulate additions such as aluminum or graphite powders, as well as metal and carbon fibers can also be incorporated therein. Particulate and/or fibrous additions can be introduced into molten phase change materials which can then be cast into various shapes. After the phase change materials have solidified, the additions will remain dispersed throughout the matrix of the cast solid. The polyol is in contact with at least one material selected from the group consisting of metals, carbon, siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, and mixtures thereof.

  2. Composite materials for thermal energy storage

    DOE Patents [OSTI]

    Benson, David K. (Golden, CO); Burrows, Richard W. (Conifer, CO); Shinton, Yvonne D. (Northglenn, CO)

    1986-01-01T23:59:59.000Z

    The present invention discloses composite material for thermal energy storage based upon polyhydric alcohols, such as pentaerythritol, trimethylol ethane (also known as pentaglycerine), neopentyl glycol and related compounds including trimethylol propane, monoaminopentaerythritol, diamino-pentaerythritol and tris(hydroxymethyl)acetic acid, separately or in combinations, which provide reversible heat storage through crystalline phase transformations. These phase change materials do not become liquid during use and are in contact with at least one material selected from the group consisting of metals, carbon siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, porous rock, and mixtures thereof. Particulate additions, such as aluminum or graphite powders, as well as metal and carbon fibers can also be incorporated therein. Particulate and/or fibrous additions can be introduced into molten phase change materials which can then be cast into various shapes. After the phase change materials have solidified, the additions will remain dispersed throughout the matrix of the cast solid. The polyol is in contact with at least one material selected from the group consisting of metals, carbon siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, and mixtures thereof.

  3. Geochemical evolution of Mexicali Valley groundwaters

    SciTech Connect (OSTI)

    Makdisi, R.S.; Truesdell, A.H.; Thompson, J.M.; Coplen, T.B.; Sanchez R., J.

    1982-08-10T23:59:59.000Z

    Isotopic and chemical compositions of Mexicali Valley groundwaters vary widely. Observed variations reflect different water origins, mineral-water reactions, lateral variations of delta facies as well as evaporation. Regional treatment of the groundwater data shows that northern and central regions are a mixture of old and new Colorado River water. Variations in water chemistry result from different groundwaters origins and the effects of lateral delta facies changes. Dissolution of gypsum and precipitation of carbonates, silicates, and phosphates are suggested. The eastern Mesa de San Luis and southern region water originates primarily from the Gila River catchment area. This water is undersaturated with respect to gypsum and carbonates and is oversaturated with respect to silicates. Most of the western groundwaters are a mixture of Colorado River and geothermal waters in the proximity of the Cerro Prieto geothermal field. Recharge to the geothermal aquifer is from the west as well as the north and east. Calcite is being precipitated out as the groundwater temperatures rise in response to the geothermal anomaly. Other western groundwaters reflect a dominant mixture of Colorado River water and evaporated lake water. Some Western groundwater samples suggest dilution by local rainwater and/or irrigation water.

  4. Todilto Formation: a Jurassic salina and its petroleum potential in east-central New Mexico

    SciTech Connect (OSTI)

    Lucas, S.G.; Kietzke, K.K.

    1986-03-01T23:59:59.000Z

    Todilto Formation of northern New Mexico and southwestern Colorado was deposited during the Middle Jurassic (middle Callovian) by a landlocked, saline lake (salina) developed in the Entrada erg. Evaporative pumping drew marine water from the Curtis sea in eastern Utah, which percolated through porous Entrada dune sands into the salina basin. The Todilto salina deposited organic-rich limestone (source rock) within a porous eolian sandstone (reservoir rock). In the San Juan basin, organic-rich Todilto limestones are a primary source of Entrada oil. There, the Todilto Limestone is generally overlain by a thick, impermeable gypsum sequence that allows Todilto hydrocarbons to migrate only into the underlying Entrada. In east-central New Mexico, the Todilto limestones pinch out into the Entrada and are not overlain by gypsum. Therefore, Todilto hydrocarbons should migrate either into the main Entrada body below the Todilto or into the Exeter member of the Entrada above. The Todilto/Entrada in east-central New Mexico has generally been overlooked in oil exploration because of its limited outcrop area and because burial depths did not seem sufficient for hydrocarbon maturation. However, until the late Cenozoic, the Todilto probably was continuous from western Quay County to the Four Corners, and east-central New Mexico was covered by a thick sequence of Cretaceous marine rocks. Furthermore, migrating Todilto hydrocarbons need not be restricted to existing Todilto outcrops, but may be expected up Entrada paleodip wherever porosity and stratigraphic traps allow accumulation.

  5. Clinoptilolite and associated authigenic minerals in Miocene tuffaceous rocks in the Goose Creek Basin, Cassia County, Idaho

    SciTech Connect (OSTI)

    Brownfield, M.E.; Hildebrand, R.T.

    1985-01-01T23:59:59.000Z

    Miocene tuffaceous fluviolacustrine deposits in the southeastern part of the Goose Creek basin contain a variety of authigenic minerals, including clinoptilolite, smectite, pyrite, gypsum, and calcite. Clinoptilolite is the primary mineral in the diagenetically altered rhyolitic vitric tuffs in the study area. These zeolitic tuffs locally attain thicknesses of as much as 30 meters. Examinations of samples of the altered tuff beds using the scanning electron microscope reveal that the clinoptilolite usually occurs as clean, well-formed tabular crystals about 0.005 mm across in a matrix of smectite. Prismatic clinoptilolite crystals, as much as 0.06 mm long, are present in the larger vugs. During the Miocene, thick beds of air-fall rhyolitic vitric volcanic ash accumulated in the Goose Creek basin in a coalescing fluviolacustrine depositional setting. In the southeastern part of the basin, the volcanic ash was deposited in a lacustrine fan delta, where it was partly reworked and interbedded with sandstone and siltstone. Diagenetic alteration of the ash beds proceeded in an open hydrologic system. Solution and hydrolysis by ground water initially altered the glass shards to form smectite and silica gel. Clinoptilolite subsequently precipitated on the altered shard surfaces. The paragenesis of pyrite, gypsum, and calcite in the zeolitic tuffs is uncertain.

  6. Advanced Flue Gas Desulfurization (AFGD) Demonstration Project, A DOE Assessment

    SciTech Connect (OSTI)

    National Energy Technology Laboratory

    2001-08-31T23:59:59.000Z

    The AFGD process as demonstrated by Pure Air at the Bailly Station offers a reliable and cost-effective means of achieving a high degree of SO{sub 2} emissions reduction when burning high-sulfur coals. Many innovative features have been successfully incorporated in this process, and it is ready for widespread commercial use. The system uses a single-loop cocurrent scrubbing process with in-situ oxidation to produce wallboard-grade gypsum instead of wet sludge. A novel wastewater evaporation system minimizes effluents. The advanced scrubbing process uses a common absorber to serve multiple boilers, thereby saving on capital through economies of scale. Major results of the project are: (1) SO{sub 2} removal of over 94 percent was achieved over the three-year demonstration period, with a system availability exceeding 99.5 percent; (2) a large, single absorber handled the combined flue gas of boilers generating 528 MWe of power, and no spares were required; (3) direct injection of pulverized limestone into the absorber was successful; (4) Wastewater evaporation eliminated the need for liquid waste disposal; and (5) the gypsum by-product was used directly for wallboard manufacture, eliminating the need to dispose of waste sludge.

  7. Substrate structures for InP-based devices

    SciTech Connect (OSTI)

    Wanlass, M.W.; Sheldon, P.

    1990-10-16T23:59:59.000Z

    A substrate structure for an InP-based semiconductor device having an InP based film is described. The substrate structure includes a substrate region having a lightweight bulk substrate and an upper GaAs layer. An interconnecting region is disposed between the substrate region and the InP-based device. The interconnecting region includes a compositionally graded intermediate layer substantially lattice-matched at the opposite end to the InP=based film. The interconnecting region further includes a dislocation mechanism disposed between the GaAs layer and the InP-based film in cooperation with the graded intermediate layer, the buffer mechanism blocking and inhibiting propagation of threading dislocations between the substrate region, and the InP-based device.

  8. High-speed epitaxy using supersonic molecular jets

    SciTech Connect (OSTI)

    Eres, D.

    1990-01-01T23:59:59.000Z

    This paper discusses the use of supersonic jets of gaseous source molecules in thin films growth. Molecular jets in free form with no skimmers or collimators in the nozzle-substrate path were used in the investigation of basic film growth processes and in practical film growth applications. The Ge growth rates were found to depend linearly on the digermane jet intensity. Furthermore, the film thickness distributions showed excellent agreement with the distribution of digermane molecules in the jet. High epitaxial Ge growth rates were achieved on GaAs (100) substrates by utilizing high-intensity pulsed jets. The practical advantages and limitations of this film growth technique are evaluated, based on the results of microstructural and electrical measurements of heteroepitaxial Ge films on GaAs (100) substrates. 8 refs., 4 figs.

  9. Non-Destructive Spent Fuel Characterization with Semi-Conducting Gallium Arsinde Neutron Imaging Arrays

    SciTech Connect (OSTI)

    Douglas S. McGregor; Holly K. Gersch; Jeffrey D. Sanders; John C. Lee; Mark D. Hammig; Michael R. Hartman; Yong Hong Yang; Raymond T. Klann; Brian Van Der Elzen; John T. Lindsay; Philip A. Simpson

    2002-01-30T23:59:59.000Z

    High resistivity bulk grown GaAs has been used to produce thermal neutron imaging devices for use in neutron radiography and characterizing burnup in spent fuel. The basic scheme utilizes a portable Sb/Be source for monoenergetic (24 keV) neutron radiation source coupled to an Fe filter with a radiation hard B-coated pixellated GaAs detector array as the primary neutron detector. The coated neutron detectors have been tested for efficiency and radiation hardness in order to determine their fitness for the harsh environments imposed by spent fuel. Theoretical and experimental results are presented, showing detector radiation hardness, expected detection efficiency and the spatial resolution from such a scheme. A variety of advanced neutron detector designs have been explored, with experimental results achieving 13% thermal neutron detection efficiency while projecting the possibility of over 30% thermal neutron detection efficiency.

  10. AlGaAs/InGaAsN/GaAs PnP double heterojunction bipolar transistor

    SciTech Connect (OSTI)

    Chang, P.C.; Baca, A.G.; Li, N.Y.; Sharps, P.R.; Hou, H.Q.; Laroche, J.R.; Ren, F.

    2000-01-11T23:59:59.000Z

    The authors have demonstrated a functional MOCVD-grown AlGaAs/InGaAsN/GaAsPnP DHBT that is lattice matched to GaAs and has a peak current gain ({beta}) of 25. Because of the smaller bandgap (E{sub g}=1.20eV)of In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01} used for the base layer, this device has a low V{sub ON} of 0.79 V, 0.25 V lower than in a comparable Pnp AlGaAs/GaAs HBT. The BV{sub CEO} is 12 V, consistent with its GaAs collector thickness and doping level.

  11. Carrier transfer from InAs quantum dots to ErAs metal nanoparticles

    SciTech Connect (OSTI)

    Haughn, C. R.; Chen, E. Y.; Zide, J. M. O.; Doty, M. F., E-mail: doty@udel.edu [Department of Materials Science and Engineering, University of Delaware, Newark, Delaware 19716 (United States); Steenbergen, E. H.; Bissell, L. J.; Eyink, K. G. [AFRL/RXAN, Wright Patterson AFB, Ohio 45433 (United States)

    2014-09-08T23:59:59.000Z

    Erbium arsenide (ErAs) is a semi-metallic material that self-assembles into nanoparticles when grown in GaAs via molecular beam epitaxy. We use steady-state and time-resolved photoluminescence to examine the mechanism of carrier transfer between indium arsenide (InAs) quantum dots and ErAs nanoparticles in a GaAs host. We probe the electronic structure of the ErAs metal nanoparticles (MNPs) and the optoelectronic properties of the nanocomposite and show that the carrier transfer rates are independent of pump intensity. This result suggests that the ErAs MNPs have a continuous density of states and effectively act as traps. The absence of a temperature dependence tells us that carrier transfer from the InAs quantum dots to ErAs MNPs is not phonon assisted. We show that the measured photoluminescence decay rates are consistent with a carrier tunneling model.

  12. Axial strain in GaAs/InAs core-shell nanowires

    SciTech Connect (OSTI)

    Biermanns, Andreas; Pietsch, Ullrich [Universitaet Siegen, Festkoerperphysik, 57068 Siegen (Germany)] [Universitaet Siegen, Festkoerperphysik, 57068 Siegen (Germany); Rieger, Torsten; Gruetzmacher, Detlev; Ion Lepsa, Mihail [Peter Gruenberg Institute (PGI-9), Forschungszentrum, 52425 Juelich (Germany) [Peter Gruenberg Institute (PGI-9), Forschungszentrum, 52425 Juelich (Germany); JARA-Fundamentals of Future Information Technology, 52425 Juelich (Germany); Bussone, Genziana [Universitaet Siegen, Festkoerperphysik, 57068 Siegen (Germany) [Universitaet Siegen, Festkoerperphysik, 57068 Siegen (Germany); ESRF, 6 rue Jules Horowitz, BP220, F-38043 Grenoble Cedex (France)

    2013-01-28T23:59:59.000Z

    We study the axial strain relaxation in GaAs/InAs core-shell nanowire heterostructures grown by molecular beam epitaxy. Besides a gradual strain relaxation of the shell material, we find a significant strain in the GaAs core, increasing with shell thickness. This strain is explained by a saturation of the dislocation density at the core-shell interface. Independent measurements of core and shell lattice parameters by x-ray diffraction reveal a relaxation of 93% in a 35 nm thick InAs shell surrounding cores of 80 nm diameter. The compressive strain of -0.5% compared to bulk InAs is accompanied by a tensile strain up to 0.9% in the GaAs core.

  13. Manipulation of emission energy in GaAs/AlGaAs core-shell nanowires with radial heterostructure

    SciTech Connect (OSTI)

    Barbosa, B. G.; Arakaki, H.; Souza, C. A. de; Pusep, Yu. A. [Instituto de Fisica de São Carlos, Universidade de São Paulo, 13560-970 Sao Carlos, SP (Brazil)

    2014-03-21T23:59:59.000Z

    Photoluminescence was studied in GaAs/AlGaAs nanowires (NWs) with different radial heterostructures. We demonstrated that manipulation of the emission energy may be achieved by appropriate choice of the shell structure. The emission at highest energy is generated in the NWs with tunneling thin AlGaAs inner shell and thin GaAs outer shell due to recombination of the photoexcited electrons confined in the outer shell with the holes in the core. Lower energy emission was shown to occur in the NWs with thick outer shell grown in the form of a short-period GaAs/AlGaAs multiple quantum well structure. In this case, the tunneling probability through the multiple quantum wells controls the energy emitted by the NWs. The doping of core results in dominated low energy emission from the GaAs core.

  14. CEBAF 200 kV Inverted Electron Gun

    SciTech Connect (OSTI)

    J.M. Grames, P.A. Adderley, J. Clark, J. Hansknecht, M. Poelker, M.L. Stutzman, R. Suleiman, K.E.L. Surles-Law

    2011-03-01T23:59:59.000Z

    Two DC high voltage GaAs photoguns have been built at Jefferson Lab based on a compact inverted insulator design. One photogun provides the polarized electron beam at CEBAF and operates at 130 kV bias voltage. The other gun is used for high average current lifetime studies at a dedicated test facility and has been operated at bias voltage up to 225 kV. The advantages of higher DC voltage for CEBAF include reduced space-charge emittance growth and the potential for prolonged photocathode lifetime. However, a consequence of operating at higher voltages is the increased likelihood of field emission or breakdown, both of which are unacceptable. Highlights of the R&D studies leading toward a production 200keV GaAs photogun for CEBAF will be presented.

  15. Towards a graphene-based quantum impedance standard

    SciTech Connect (OSTI)

    Kalmbach, C.-C.; Schurr, J., E-mail: juergen.schurr@ptb.de; Ahlers, F. J.; Müller, A. [Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig (Germany); Novikov, S.; Lebedeva, N. [Department of Micro- and Nanosciences, Aalto University, Micronova, Tietotie 3, 02150 Espoo (Finland); Satrapinski, A. [MIKES, Tekniikantie 1, P.O. Box, 02151 Espoo (Finland)

    2014-08-18T23:59:59.000Z

    Precision measurements of the quantum Hall resistance with alternating current (ac) in the kHz range were performed on epitaxial graphene in order to assess its suitability as a quantum standard of impedance. The quantum Hall plateaus measured with alternating current were found to be flat within one part in 10{sup 7}. This is much better than for plain GaAs quantum Hall devices and shows that the magnetic-flux-dependent capacitive ac losses of the graphene device are less critical. The observed frequency dependence of about ?8?×?10{sup ?8}/kHz is comparable in absolute value to the positive frequency dependence of plain GaAs devices, but the negative sign is attributed to stray capacitances which we believe can be minimized by a careful design of the graphene device. Further improvements thus may lead to a simpler and more user-friendly quantum standard for both resistance and impedance.

  16. Comment on "Cyclotron resonance study of the electron and hole velocity in graphene monolayers"

    E-Print Network [OSTI]

    S. C. Tiwari

    2007-05-26T23:59:59.000Z

    In this comment it is pointed out that the electron velocity of the same order as observed in graphene had been measured in GaAs submicron devices long ago. Particle- antiparticle asymmetry related with electron and hole effective masses in graphene seems puzzling as hole in a condensed matter system cannot be treated as anti-electron. It is argued that there should be a universal electrodynamics for QHE and superconductivity. In this context attention is drawn to the new approach based on massless electron and the interpretation that magnetic field represents angular momentum of the photon fluid. Measurement of electron velocity in graphene and GaAs in parallel is suggested for testing the massless electrodynamics.

  17. All optical method for investigation of spin and charge transport in semiconductors: Combination of spatially and time-resolved luminescence

    SciTech Connect (OSTI)

    Cadiz, F.; Paget, D.; Grebenkov, D.; Korb, J. P.; Rowe, A. C. H. [Physique de la matière condensée, Ecole Polytechnique, CNRS, 91128 Palaiseau (France); Barate, P.; Amand, T. [Université de Toulouse, INSA-CNRS-UPS, 31077 Toulouse Cedex (France); Arscott, S.; Peytavit, E. [Institut d'Electronique, de Microélectronique et de Nanotechnologie (IEMN), University of Lille, CNRS, Avenue Poincaré, Cité Scientifique, 59652 Villeneuve d'Ascq (France)

    2014-07-14T23:59:59.000Z

    A new approach is demonstrated for investigating charge and spin diffusion as well as surface and bulk recombination in unpassivated doped semiconductors. This approach consists in using two complementary, conceptually related, techniques, which are time-resolved photoluminescence (TRPL) and spatially resolved microluminescence (?PL) and is applied here to p{sup +} GaAs. Analysis of the sole TRPL signal is limited by the finite risetime. On the other hand, it is shown that joint TRPL and ?PL can be used to determine the diffusion constant, the bulk recombination time, and the spin relaxation time. As an illustration, the temperature variation of these quantities is investigated for p{sup +} GaAs.

  18. Four-Terminal Mechanically Stacked GaAs/Si Tandem Solar Cells

    E-Print Network [OSTI]

    Hassan, S

    2015-01-01T23:59:59.000Z

    This study investigates a four-terminal mechanically stacked double junction photovoltaic device based on GaAs as a top subcell and Si as a bottom subcell. Unlike two terminal monolithically series connected double junction photovoltaics, four-terminal mechanically stacked devices benefit from the ability to choose a combination of materials that are not constrained to lattice matching condition. GaAs top subcell is the best sensitive to visible light and Si bottom subcell is chosen to be grown on Si substrate which has relatively low cost. Moreover, the carriers generated by each subcell is collected independently to the external circuit. This electrical isolation of the subcells ensures higher efficiency, where no current matching nor tunnel junctions and related losses exist. A conversion efficiency of the device with a thickness in the order of 10 microns surpassed 27%.

  19. Multi-phonon-assisted absorption and emission in semiconductors and its potential for laser refrigeration

    E-Print Network [OSTI]

    Khurgin, Jacob B

    2014-01-01T23:59:59.000Z

    Laser cooling of semiconductors has been an elusive goal for many years, and while attempts to cool the narrow gap semiconductors such as GaAs are yet to succeed, recently, net cooling has been attained in a wider gap CdS. This raises the question of whether wider gap semiconductors with higher phonon energies and stronger electron-phonon coupling are better suitable for laser cooling. In this work we develop a straightforward theory of phonon-assisted absorption and photoluminescence of semiconductors that involves more than one phonon and use to examine wide gap materials, such as GaN and CdS and compare them with GaAs. The results indicate that while strong electron-phonon coupling in both GaN and CdS definitely improves the prospects of laser cooling, large phonon energy in GaN may be a limitation, which makes CdS a better prospect for laser cooling.

  20. Small quantum dots of diluted magnetic III-V semiconductor compound

    E-Print Network [OSTI]

    Pozhar, Liudmila A

    2012-01-01T23:59:59.000Z

    In this chapter quantum many body theoretical methods have been used to study properties of GaAs - and InAs - based, small semiconductor compound quantum dots (QDs) containing manganese or vanadium atoms. Interest to such systems has grown since experimental synthesis of nanoscale magnetic semiconductors, that is, nanoscale semiconductor compounds with enhanced magnetic properties. This enhancement is achieved by several methods, and in particular by doping common semiconductor compounds with some atoms, such as Mn or V. Experimental studies indicate that the electron spin density in the case of thin nanoscale magnetic semiconductor films and QDs may be delocalized. As described in this chapter, quantum many body theory-based, computational synthesis (i.e., virtual synthesis) of tetrahedral symmetry GaAs and InAs small pyramidal QDs doped with sabstitutional Mn or V atoms proves that such QDs are small magnetic molecules that indeed, possess delocalized and polarized electron spin density. Such delocalization...