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Sample records for ga ni za

  1. Energy absorption in Ni-Mn-Ga/ polymer composites

    E-Print Network [OSTI]

    Feuchtwanger, Jorge

    2006-01-01

    In recent years Ni-Mn-Ga has attracted considerable attention as a new kind of actuator material. Off-stoichiometric single crystals of Ni2MnGa can regularly exhibit 6% strain in tetragonal martensites and orthorhombic ...

  2. The first principle study of Ni{sub 2}ScGa and Ni{sub 2}TiGa

    SciTech Connect (OSTI)

    Özduran, Mustafa; Turgut, Kemal; Arikan, Nihat; ?yigör, Ahmet; Candan, Abdullah

    2014-10-06

    We computed the electronic structure, elastic moduli, vibrational properties, and Ni{sub 2}TiGa and Ni{sub 2}ScGa alloys in the cubic L2{sub 1} structure. The obtained equilibrium lattice constants of these alloys are in good agreement with available data. In cubic systems, there are three independent elastic constants, namely C{sub 11}, C{sub 12} and C{sub 44}. We calculated elastic constants in L2{sub 1} structure for Ni{sub 2}TiGa and Ni{sub 2}ScGa using the energy-strain method. The electronic band structure, total and partial density of states for these alloys were investigated within density functional theory using the plane-wave pseudopotential method implemented in Quantum-Espresso program package. From band structure, total and projected density of states, we observed metallic characters of these compounds. The electronic calculation indicate that the predominant contributions of the density of states at Fermi level come from the Ni 3d states and Sc 3d states for Ni{sub 2}TiGa, Ni 3d states and Sc 3d states for Ni{sub 2}ScGa. The computed density of states at Fermi energy are 2.22 states/eV Cell for Ni{sub 2}TiGa, 0.76 states/eV Cell for Ni{sub 2}ScGa. The vibrational properties were obtained using a linear response in the framework at the density functional perturbation theory. For the alloys, the results show that the L2{sub 1} phase is unstable since the phonon calculations have imagine modes.

  3. Understanding and development of combined acoustic and magnetic actuation of Ni?MnGa single crystals

    E-Print Network [OSTI]

    Techapiesancharoenkij, Ratchatee, 1979-

    2007-01-01

    Ni-Mn-Ga based ferromagnetic shape memory alloys (FSMAs) have emerged as a promising new class of active materials capable of producing a large (several %) magnetic-field-induced strain (MFIS). FSMAs still have several ...

  4. Computational Thermodynamics of CoNiGa High Temperature Shape Memory Alloys 

    E-Print Network [OSTI]

    Chari, Arpita

    2012-10-19

    Shape Memory Alloys (SMAs) are advanced materials with interesting properties such as pseudoelasticity (PE) and the shape memory effect (SME). Recently, the CoNiGa system has emerged as the basis for very promising High ...

  5. Structure and magnetic properties of Ce?(Ni/Al/Ga)??-A...

    Office of Scientific and Technical Information (OSTI)

    Ce(NiAlGa)-A new phase with the LaAl structure type Janka, Oliver Univ. of California, Davis, CA (United States); Westfalische Wilhelms-Universitat, Munster...

  6. Magnetic field-induced phase transformation and variant reorientation in Ni2MnGa and NiMnCoIn magnetic shape memory alloys 

    E-Print Network [OSTI]

    Karaca, Haluk Ersin

    2009-05-15

    The purpose of this work is to reveal the governing mechanisms responsible for the magnetic field-induced i) martensite reorientation in Ni2MnGa single crystals, ii) stress-assisted phase transformation in Ni2MnGa single ...

  7. Systematic analysis of the crystal structure, chemical ordering, and microstructure of Ni-Mn-Ga ferromagnetic shape memory alloys

    E-Print Network [OSTI]

    Richard, Marc Louis

    2005-01-01

    Ni-n-Ga based ferromagnetic shape-memory alloys (FSMAs) have shown great promise as an active material that yields a large output strain over a range of actuation frequencies. The maximum strain has been reported to be 6% ...

  8. Elastic Constants of Ni-Mn-Ga Magnetic Shape Memory Alloys

    SciTech Connect (OSTI)

    Stipcich, M. [Universitat de Barcelona; Manosa, L. [Universitat de Barcelona; Planes, A. [Universitat de Barcelona; Morin, M. [INSA de Lyon; Zarestky, Jerel L [ORNL; Lograsso, Tom [Ames Laboratory; Stassis, C. [Ames Laboratory

    2004-01-01

    We have measured the adiabatic second order elastic constants of two Ni-Mn-Ga magnetic shape memory crystals with different martensitic transition temperatures, using ultrasonic methods. The temperature dependence of the elastic constants has been followed across the ferromagnetic transition and down to the martensitic transition temperature. Within experimental errors no noticeable change in any of the elastic constants has been observed at the Curie point. The temperature dependence of the shear elastic constant C' has been found to be very different for the two alloys. Such a different behavior is in agreement with recent theoretical predictions for systems undergoing multi-stage structural transitions.

  9. Structure and magnetic properties of Ce?(Ni/Al/Ga)??—A new phase with the La?Al?? structure type

    SciTech Connect (OSTI)

    Janka, Oliver; Shang, Tian; Baumbach, Ryan E.; Bauer, Eric D.; Thompson, Joe D.; Kauzlarich, Susan M.

    2015-03-01

    Single crystals of Ce?(Ni/Al/Ga)?? were obtained from an Al flux reaction. Single crystals of the title compound crystallizing in the orthorhombic space group Immm (No. 71, Z = 2) with a = 436.38(14), b = 1004.5(3) and c = 1293.4(4) pm. This is a standardized unit cell of the previously published La?Al?? structure type. Wavelength dispersive microprobe provides the composition of Ce?.?????Ni?.?????Al?.?????Ga?.?????. Single crystal refinement provides the composition Ce?Ni?.??Al?.??Ga?.?? with substitution of the Ni and Ga on the Al1 and Al4 sites with the Al2 and Al3 solely occupied by Al. Magnetic susceptibility measurements reveal antiferromagnetic ordering with TN = 4.8 K and there is no evidence for a ferromagnetic ordering that has been reported for Ce?Al??. The effective magnetic moment was found to be ?eff = 1.9?B/Ce, which is lower than the expected value for trivalent Ce (2.54?B/Ce).

  10. Slovarsko gradivo Fti?arjevega romana Za nápršnjek vedríne

    E-Print Network [OSTI]

    Ul?nik, Natalija

    2010-02-01

    — 125 — Slovarsko gradivo Fti?arjevega romana Za nápršnjek vedríne1 natali ja ul?nik Univerza v Mariboru, Filozofska fakulteta, Koroška cesta 160, SI – 2000 Maribor, natalija.ulcnik@uni-mb.si Za nápršnjek vedríne (2004, 2006) avtorja Jožeta... podonavskega in alpskega prostora, ki ga financira Agencija za raziskovalno dejavnost RS; odgovorni nosilec projekta je red. prof. dr. Marko Jesenšek. SCN III/1 [2010], 125–156 — 126 — Slavia Centralis 1/2010 Natalija Ul?nik 0 Uvod Jože Fti?ar, dialektolog...

  11. In-situ neutron diffraction study of martensitic variant redistribution in polycrystalline Ni-Mn-Ga alloy under cyclic thermo-mechanical treatment

    SciTech Connect (OSTI)

    Li, Zongbin; Zou, Naifu; Zhao, Xiang; Zuo, Liang, E-mail: lzuo@mail.neu.edu.cn, E-mail: yudong.zhang@univ-lorraine.fr [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110819 (China); Zhang, Yudong, E-mail: lzuo@mail.neu.edu.cn, E-mail: yudong.zhang@univ-lorraine.fr; Esling, Claude [Laboratoire d'Étude des Microstructures et de Mécanique des Matériaux (LEM3), CNRS UMR 7239, Université de Lorraine, 57045 Metz (France); Laboratory of Excellence on Design of Alloy Metals for low-mAss Structures (DAMAS), Université de Lorraine, 57045 Metz (France); Gan, Weimin [German Engineering Materials Science Centre (GEMS), Helmholtz-Zentrum Geesthacht (HZG) Outstation at FRM II, D-85748, Garching (Germany)

    2014-07-14

    The influences of uniaxial compressive stress on martensitic transformation were studied on a polycrystalline Ni-Mn-Ga bulk alloy prepared by directional solidification. Based upon the integrated in-situ neutron diffraction measurements, direct experimental evidence was obtained on the variant redistribution of seven-layered modulated (7M) martensite, triggered by external uniaxial compression during martensitic transformation. Large anisotropic lattice strain, induced by the cyclic thermo-mechanical treatment, has led to the microstructure modification by forming martensitic variants with a strong ?0 1 0?{sub 7M} preferential orientation along the loading axis. As a result, the saturation of magnetization became easier to be reached.

  12. Konferenca Komisije za slovansko besedotvorje pri MSK

    E-Print Network [OSTI]

    Breznik, Irena Stramlji?

    2011-02-01

    imenih za moški in ženski spol z vidika sistemskih možno- sti in besedilnih realizacij v bolgarš?ini. Mesto besedotvornih priložnostnic v oglasih je zanimalo dve referntki: E. Korjakowcewa je predstavila tvorbeno kompresijo v oglasih v razmerju tvor... v tekstih. V Radeva (Sofija) pa je razpravljala o razmerju besedo- tvornih in leksikalnih parametrov v tvorjenkah z vidika tvorbenih zmožno- sti in leksikalne norme. Mestu izimenske leksike v besedo- tvorju sta bila posve?ena dva referata. C...

  13. Study of the N=50 major shell effect close to $^{78}$Ni : First evidence of a weak coupling structure in $^{83}\\_{32}$Ge$\\_{51}$ and three-proton configuration states in $^{81}\\_{31}$Ga$\\_{50}$

    E-Print Network [OSTI]

    D. Verney; F. Ibrahim; O. Perru; O. Bajeat; C. Bourgeois; M. Ducourtieux; C. Donzaud; S. Essabaa; S. Gales; L. Gaudefroy; D. Guillemaud-Mueller; F. Hammache; C. Lau; H. Lefort; F. Le Blanc; A. C. Mueller; F. Pougheon; B. Roussiere; J. Sauvage; O. Sorlin

    2006-10-06

    New levels were attributed to $^{81}\\_{31}$Ga$\\_{50}$ and $^{83}\\_{32}$Ge$\\_{51}$ which were fed by the $\\beta$-decay of their respective mother nuclei $^{81}\\_{30}$Zn$\\_{51}$ and $^{83}\\_{31}$Ga$\\_{52}$ produced by fission at the "PARRNe" ISOL set-up installed at the Tandem accelerator of the Institut de Physique Nucl\\'eaire, Orsay. We show that the low energy structure of $^{81}\\_{31}$Ga$\\_{50}$ and $^{83}\\_{32}$Ge$\\_{51}$ can easily be explained within the natural hypothesis of a strong energy gap at N=50 and a doubly-magic character for $^{78}$Ni.

  14. Influence of boron on the microstructural and mechanical properties of Ni{sub 53.5}Mn{sub 26.0}Ga{sub 20.5} shape memory alloy

    SciTech Connect (OSTI)

    Ramudu, M., E-mail: macrams2@gmail.com; Kumar, A. Satish, E-mail: macrams2@gmail.com; Seshubai, V., E-mail: macrams2@gmail.com [School of Physics, University of Hyderabad, Central University P. O., Hyderabad - 500 046 (India); Rajasekharan, T. [Department of Physics, Rajiv Gandhi University of Knowledge Technologies, IIIT-Campus, Gachibowli, Hyderabad - 500 032 (India)

    2014-04-24

    Boron addition to Ni{sub 53.5}Mn{sub 26.0}Ga{sub 20.5} alloy is found to modify the microstructure and mechanical properties substantially. Studies on (Ni{sub 53.5}Mn{sub 26.0}Ga{sub 20.5})B{sub x} alloys reveal that boron addition causes grain refinement which led to an increase in compressive strength in x=0.5 alloy which also retained multimode twinning. Substantial second phase segregation rich in Ni was seen at grain boundaries, the extent of which increased with boron content. This led to a compositional shift in the matrix phase which resulted in a reduction in the martensitic transformation temperature and which in turn caused an easy deformation at low stresses and suppression of multimode twinning in x=1.0 alloy.

  15. Low Energy States of $^{81}_{31} Ga_{50}$ : Elements on the Doubly-Magic Nature of $^{78}$Ni

    E-Print Network [OSTI]

    David Verney; C. Bourgeois; C. Donzaud; S. Essabaa; S. Gales; L. Gaudefroy; D. Guillemaud-Mueller; F. Hammache; F. Ibrahim; C. Lau; F. Le Blanc; A. C. Mueller; O. Perru; F. Pougheon; B. Roussiere; J. Sauvage; O. Sorlin; D. Verney

    2007-01-26

    Excited levels were attributed to $^{81}_{31}$Ga$_{50}$ for the first time which were fed in the $\\beta$-decay of its mother nucleus $^{81}$Zn produced in the fission of $^{nat}$U using the ISOL technique. We show that the structure of this nucleus is consistent with that of the less exotic proton-deficient N=50 isotones within the assumption of strong proton Z=28 and neutron N=50 effective shell effects.

  16. Control of domain wall pinning by localised focused Ga?{sup +} ion irradiation on Au capped NiFe nanowires

    SciTech Connect (OSTI)

    Burn, D. M. Atkinson, D.

    2014-10-28

    Understanding domain wall pinning and propagation in nanowires are important for future spintronics and nanoparticle manipulation technologies. Here, the effects of microscopic local modification of the magnetic properties, induced by focused-ion-beam intermixing, in NiFe/Au bilayer nanowires on the pinning behavior of domain walls was investigated. The effects of irradiation dose and the length of the irradiated features were investigated experimentally. The results are considered in the context of detailed quasi-static micromagnetic simulations, where the ion-induced modification was represented as a local reduction of the saturation magnetization. Simulations show that domain wall pinning behavior depends on the magnitude of the magnetization change, the length of the modified region, and the domain wall structure. Comparative analysis indicates that reduced saturation magnetisation is not solely responsible for the experimentally observed pinning behavior.

  17. http://www.up.ac.za/academic/fabi/tpcp/pamphlets/phytophthora.htm PHYTOPHTHORA ROOT AND COLLAR

    E-Print Network [OSTI]

    http://www.up.ac.za/academic/fabi/tpcp/pamphlets/phytophthora.htm PHYTOPHTHORA ROOT AND COLLAR ROT cold weather the fungus survives as oospores, chlamydospores http://www.up.ac.za/academic/fabi/tpcp/pamphlets/phytophthora.htm (1 of 4) [2002/02/26 01:54:52] #12;http://www.up.ac.za/academic/fabi/tpcp/pamphlets

  18. http://www.up.ac.za/academic/fabi/tpcp/pamphlets/dothistroma.htm DOTHISTROMA NEEDLE BLIGHT

    E-Print Network [OSTI]

    http://www.up.ac.za/academic/fabi/tpcp/pamphlets/dothistroma.htm DOTHISTROMA NEEDLE BLIGHT is necessary and routinely applied. At present, the disease is not http://www.up.ac.za/academic/fabi/tpcp/pamphlets/dothistroma.htm (1 of 2) [2002/02/26 01:53:43] #12;http://www.up.ac.za/academic/fabi/tpcp/pamphlets

  19. http://www.up.ac.za/academic/fabi/tpcp/pamphlets/mycosphaerella.htm MYCOSPHAERELLA

    E-Print Network [OSTI]

    http://www.up.ac.za/academic/fabi/tpcp/pamphlets/mycosphaerella.htm MYCOSPHAERELLA LEAF DISEASES leaf blotch develop adult leaves rapidly and are not seriously http://www.up.ac.za/academic/fabi/tpcp/pamphlets/mycosphaerella.htm (1 of 3) [2002/02/26 01:54:11] #12;http://www.up.ac.za/academic/fabi/tpcp/pamphlets

  20. http://www.up.ac.za/academic/fabi/tpcp/pamphlets/coniothyrium.htm CONIOTHYRIUM CANKER OF

    E-Print Network [OSTI]

    http://www.up.ac.za/academic/fabi/tpcp/pamphlets/coniothyrium.htm CONIOTHYRIUM CANKER OF EUCALYPTUS risk areas. Coniothyrium canker and spores of the fungus. http://www.up.ac.za/academic/fabi/tpcp/pamphlets/coniothyrium.htm (1 of 2) [2002/02/26 01:49:46] #12;http://www.up.ac.za/academic/fabi/tpcp/pamphlets

  1. ENGINEERING & THE BUILT ENVIRONMENT www.wits.ac.za/engineering

    E-Print Network [OSTI]

    Wagner, Stephan

    29 ENGINEERING & THE BUILT ENVIRONMENT www.wits.ac.za/engineering #12;30 Wits fact The Wits Mining, management, sociology, migration, eco- nomics, engineering, healthcare, materials science, geology, energy of Mechanical, Industrial and Aeronautical Engineering was awarded an Honorary Fellowship of the Royal

  2. High strain in polycrystalline Ni{sub 48.8}Mn{sub 31.4}Ga{sub 19.8} Heusler alloys under overlapped static and oscillating magnetic fields

    SciTech Connect (OSTI)

    Montanher, D. Z.; Pereira, J. R. D.; Cótica, L. F.; Santos, I. A.; Gotardo, R. A. M.; Viana, D. S. F.; Garcia, D.; Eiras, J. A.

    2014-09-21

    Martensitic polycrystalline Ni{sub 48.8}Mn{sub 31.4}Ga{sub 19.8} Heusler alloys, with a stacking period of 14 atomic planes at room temperature, were innovatively processed by combining high-energy ball milling and powder metallurgy. Bulk samples were mechanically coupled to a piezoelectric material in a parallel configuration, and the mechanical deformation of the studied system due to the twin's variant motion was investigated under overlapped static and oscillating magnetic fields. A reversible and high mechanical deformation is observed when the frequency of the oscillating magnetic field is tuned with the natural vibration frequency of this system. In this condition, a linear deformation as a function of the static magnetic field amplitude occurs in the ±4 kOe range, and a mechanical deformation of 2% at 10 kOe is observed.

  3. http://www.up.ac.za/academic/fabi/tpcp/pamphlets/submission.htm SUBMISSION OF SAMPLES FOR DISEASE DIAGNOSIS

    E-Print Network [OSTI]

    http://www.up.ac.za/academic/fabi/tpcp/pamphlets/submission.htm SUBMISSION OF SAMPLES FOR DISEASE of your http://www.up.ac.za/academic/fabi/tpcp/pamphlets/submission.htm (1 of 2) [2002/02/26 01:55:27] #12;http://www.up.ac.za/academic/fabi/tpcp/pamphlets/submission.htm TYPES OF SAMPLES Samples for laboratory

  4. Shape memory response of ni2mnga and nimncoin magnetic shape memory alloys under compression 

    E-Print Network [OSTI]

    Brewer, Andrew Lee

    2009-05-15

    In this study, the shape memory response of Ni2MnGa and NiMnCoIn magnetic shape memory alloys was observed under compressive stresses. Ni2MnGa is a magnetic shape memory alloy (MSMA) that has been shown to exhibit fully ...

  5. Water and Capabilities Guest Editor of this issue: Jacqueline Goldin, jgoldin@uwc.ac.za

    E-Print Network [OSTI]

    Water and Capabilities Guest Editor of this issue: Jacqueline Goldin, jgoldin@uwc.ac.za HDCA) ------------------------------------------------------------------- Elements of Feminist Political Ecology and Capabilities (Leila Harris) Access to Water and the Capability Approach (PB Anand) Water Insecurity, Emotional Distress, and Mental Illness: Implications for Human

  6. HEALTH SCIENCES www.wits.ac.za/health The Faculty of Health Sciences has

    E-Print Network [OSTI]

    Wagner, Stephan

    41 HEALTH SCIENCES www.wits.ac.za/health #12;42 The Faculty of Health Sciences has an outstanding Lorna Jacklin, winner of the Checkers-Shoprite Woman of the Year in 2008 in the category of Health) · Bachelor of Health Sciences - BHSc: (3 years) (there are two plans - Biomedical Sciences and Biokinetics

  7. Oblikoslovje v panonski nare?ni skupini

    E-Print Network [OSTI]

    Zorko, Zinka

    2010-01-01

    glagole: nes?, neseši, neset?; nesev?, neseta, nesete; nesem?, nesete, nes?t?; za atematske glagole: jesm?, jesi, jest?; jesv?, jesta, jeste; jesm?, jeste, s?t?. Slovenski knjižni jezik – tematska spregatev: nes-em, -eš, -e; -va, -ta, -ta; -mo, -te, -jo...; atematska spregatev: sem, si, je; sva, sta, sta; smo, ste, so. Prekmurš?ina (vsi glagoli se spregajo po temati?nem vzorcu): ne?s?:n, ne?s?:š, ne?s?:; ne?s?:va (m. sp.), ne?s?:ve (ž. sp.), ne?s?:ta, ne?s?:ta; ne?s?:mo, ne?s?:te, ne?s?:jo; ?sån, ?si, ?je; s...

  8. Characterization of the gate oxide of an AlGaN/GaN high electron mobility transistor

    E-Print Network [OSTI]

    Florida, University of

    2011; published online 21 March 2011 A subnanometer thick interfacial oxide layer present between used to characterize a Ni/AlGaN interfacial oxide layer with subnanometer thickness. The semiconducting

  9. Generalized Uhlenbeck-Goudsmit hypothesis 'Magnetic' S^{a} and 'Electric' Z^{a} Spins

    E-Print Network [OSTI]

    Tomislav Ivezic

    2010-03-23

    In this paper, the connection between the dipole moment tensor D^{ab} and the spin four-tensor S^{ab} is formulated in the form of the generalized Uhlenbeck-Goudsmit hypothesis, D^{ab}=g_{S}S^{ab}. It is also found that the spin four-tensor S^{ab} can be decomposed into two 4-vectors, the usual `space-space' intrinsic angular momentum S^{a}, which will be called `magnetic' spin (mspin), and a new one, the `time-space' intrinsic angular momentum Z^{a}, which will be called `electric' spin (espin). Both spins are equally good physical quantities. Taking into account the generalized Uhlenbeck-Goudsmit hypothesis, the decomposition of S^{ab} and the decomposition of D^{ab} into the dipole moments m^{a} and d^{a}, we find that an electric dipole moment (EDM) of a fundamental particle, as a four-dimensional (4D) geometric quantity, is determined by Z^{a} and not, as generally accepted, by the spin $\\mathbf{S}$ as a 3-vector. Also it is shown that neither the T inversion nor the P inversion are good symmetries in the 4D spacetime. In this geometric approach, only the world parity W, Wx^{a}=-x^{a}, is well defined in the 4D spacetime. Some consequences for elementary particle theories and experiments that search for EDM are briefly discussed.

  10. Office +27 (0) 21 424 5351 Fax +27 (0) 21 423 4819 Email attorneys@fidfund.co.za Website www.fidfund.co.za Physical 5th Floor, Waalburg Building, 28 Wale Street, Cape Town, 8001, South Africa

    E-Print Network [OSTI]

    Wagner, Stephan

    .fidfund.co.za Physical 5th Floor, Waalburg Building, 28 Wale Street, Cape Town, 8001, South Africa Postal P O Box 3062, Cape Town, 8000, South Africa Docex Docex 154, Cape Town B M Molefe (Chief Executive Officer), A M oorr ee--mmaaiilleedd aapppplliiccaattiioonn ffoorrmmss.. Yours faithfully MR S. AFRICA BURSARY CO

  11. SCIENCE www.wits.ac.za/science Wits is the only university on the African continent which is

    E-Print Network [OSTI]

    Wagner, Stephan

    74 SCIENCE www.wits.ac.za/science #12;75 Wits fact Wits is the only university on the African examinations in the shortest possible time. The Faculty of Science has a long tradition of excellence conservation and use of our natural resources and enjoy problem solving, then the Faculty of Science at Wits

  12. Blending Cr2O3 into a NiO-Ni electrocatalyst for sustained water splitting

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

    Gong, Ming; Zhou, Wu; Kenney, Michael James; Kapusta, Rich; Cowley, Sam; Wu, Yingpeng; Lu, Bingan; Lin, Meng -Chang; Wang, Di -Yan; Yang, Jiang; et al

    2015-08-24

    The rising H2 economy demands active and durable electrocatalysts based on low-cost, earth-abundant materials for water electrolysis/photolysis. Here we report nanoscale Ni metal cores over-coated by a Cr2O3-blended NiO layer synthesized on metallic foam substrates. The Ni@NiO/Cr2O3 triphase material exhibits superior activity and stability similar to Pt for the hydrogen-evolution reaction in basic solutions. The chemically stable Cr2O3 is crucial for preventing oxidation of the Ni core, maintaining abundant NiO/Ni interfaces as catalytically active sites in the heterostructure and thus imparting high stability to the hydrogen-evolution catalyst. The highly active and stable electrocatalyst enables an alkaline electrolyzer operating at 20more »mA cm–2 at a voltage lower than 1.5 V, lasting longer than 3 weeks without decay. Thus, the non-precious metal catalysts afford a high efficiency of about 15 % for light-driven water splitting using GaAs solar cells.« less

  13. Porous GaN nanowires synthesized using thermal chemical vapor deposition

    E-Print Network [OSTI]

    Kim, Bongsoo

    nanotube-confined reaction [4], arc discharge [5], laser ablation [6], sublimation [7], pyrolysis [8O3)/ carbons with NH3 produced the large-quantity porous GaN nanowires on the iron (Fe)/nickel (Ni

  14. Ni Ni: University of California - Los Angeles

    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: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantityBonneville Power Administration wouldMass map shinesSolarNew scholarshipThreeFebruary 2015 ESH&SCSU - EnergyNi Ni:

  15. CoNiGa High Temperature Shape Memory Alloys 

    E-Print Network [OSTI]

    Dogan, Ebubekir

    2011-10-21

    Shape memory alloys (SMAs) are an important class of smart materials that have the ability to remember a shape. Current practical uses of SMAs are limited to below 100 degrees C which is the limit for the transformation ...

  16. Acetic Acid (H3COOH): GaAs; Pb; Ti Hydrochloric Acid (HCl): Al; Cr; Cu; Fe2O3; Ga; GaAs; GaN; In; Fe; Pb; Ni; NiO, Ni2O3; Sn;

    E-Print Network [OSTI]

    Garmestani, Hamid

    ferrocyanide (s) KMnO4 : potassium permanganate (s) FeCl3 : ferric chloride (s) NH4SO5 : ammonium persulfate (s

  17. AlGaN/GaN-based power semiconductor switches

    E-Print Network [OSTI]

    Lu, Bin, Ph. D. Massachusetts Institute of Technology

    2013-01-01

    AlGaN/GaN-based high-electron-mobility transistors (HEMTs) have great potential for their use as high efficiency and high speed power semiconductor switches, thanks to their high breakdown electric field, mobility and ...

  18. Metal contacts on ZnSe and GaN

    SciTech Connect (OSTI)

    Duxstad, K J [Univ. of California, Berkeley, CA (United States). Materials Science and Mineral Engineering

    1997-05-01

    Recently, considerable interest has been focused on the development of blue light emitting materials and devices. The focus has been on GaN and ZnSe, direct band gap semiconductors with bands gaps of 3.4 and 2.6 eV, respectively. To have efficient, reliable devices it is necessary to have thermally and electrically stable Ohmic contacts. This requires knowledge of the metal-semiconductor reaction behavior. To date few studies have investigated this behavior. Much information has accumulated over the years on the behavior of metals on Si and GaAs. This thesis provides new knowledge for the more ionic wide band gap semiconductors. The initial reaction temperatures, first phases formed, and phase stability of Pt, Pd, and Ni on both semiconductors were investigated. The reactions of these metals on ZnSe and GaN are discussed in detail and correlated with predicted behavior. In addition, comparisons are made between these highly ionic semiconductors and Si and GaAs. The trends observed here should also be applicable to other II-VI and III-Nitride semiconductor systems, while the information on phase formation and stability should be useful in the development of contacts for ZnSe and GaN devices.

  19. Phosphorus content effect on the magnetoelectric properties of the NiP(Ni)/PZT/NiP(Ni) cylindrical layered composites

    E-Print Network [OSTI]

    Volinsky, Alex A.

    were polarized along the radial direction after electroplating a thin Ni layer on its inside and outside surfaces. The samples were pretreated with supersonic cleaning prior to Ni electroplating composite is shown else- where [13]. The final thickness of the inside and the outside coatings

  20. Structure, transport and thermal properties of UCoGa

    SciTech Connect (OSTI)

    Purwanto, A.; Robinson, R.A.; Prokes, K.

    1994-04-01

    By means of neutron powder diffraction, we find that UCoGa crystallizes in the hexagonal ZrNiAl structure and orders ferromagnetically at low temperatures with magnetic moments stacked along the c axis. The magnetic-ordering temperature is reflected in anomalies in the temperature dependencies of the electrical resistivity and the specific heat at Tc = 47 K. Furthermore, the strong anisotropy in the electrical resistivity for i {parallel} c and i {perpendicular} c indicates a significant contribution of the magnetic anisotropy to the electrical resistivity.

  1. Influence of nuclear structure on sub-barrier hindrance in Ni+Ni fusion

    E-Print Network [OSTI]

    C. L. Jiang; K. E. Rehm; R. V. F. Janssens; H. Esbensen; I. Ahmad; B. B. Back; P. Collon; C. N. Davids; J. P. Greene; D. J. Henderson; G. Mukherjee; R. C. Pardo; M. Paul; T. O. Pennington; D. Seweryniak; S. Sinha; Z. Zhou

    2004-02-25

    Fusion-evaporation cross sections for $^{64}$Ni+$^{64}$Ni have been measured down to the 10 nb level. For fusion between two open-shell nuclei, this is the first observation of a maximum in the $S$-factor, which signals a strong sub-barrier hindrance. A comparison with the $^{58}$Ni+$^{58}$Ni, $^{58}$Ni+$^{60}$Ni, and $^{58}$Ni+$^{64}$Ni systems indicates a strong dependence of the energy where the hindrance occurs on the stiffness of the interacting nuclei.

  2. 2/6/2014 "Grain of rice" windmills to power smartphones of tomorrow -htxt.africa http://www.htxt.co.za/2014/01/13/tiny-windmills-could-power-the-gadgets-of-tomorrow/ 1/4

    E-Print Network [OSTI]

    Chiao, Jung-Chih

    2/6/2014 "Grain of rice" windmills to power smartphones of tomorrow - htxt.africa http://www.htxt.co.za/2014/01/13/tiny-windmills-could-power-the-gadgets-of-tomorrow/ 1/4 Talk to us on Twitter Follow us" windmills to power smartphones of tomorrow When you think of wind energy the first thing that springs

  3. Sample & Assay Technologies Ni-NTA Superflow

    E-Print Network [OSTI]

    Lebendiker, Mario

    March 2007 Sample & Assay Technologies Ni-NTA Superflow Cartridge Handbook For manual or FPLCTM purification of His-tagged proteins #12;2 Ni-NTA Superflow Cartridge Handbook 03/2007 Trademarks: QIAGEN, are not to be considered unprotected by law. © 2007 QIAGEN, all rights reserved. #12;Ni-NTA Superflow Cartridge Handbook 03

  4. Monopole Strength in Ni-58 

    E-Print Network [OSTI]

    Youngblood, David H.; Lui, YW.

    1991-01-01

    Differential cross-section data from 0-degrees to 8-degrees for inelastic scattering of 129 MeV alpha particles exciting Ni-58 in the region of 14-22 MeV have been analyzed to explore the existence of monopole strength at approximately E(x) = 17 Me...

  5. Polarization-engineered GaN/InGaN/GaN tunnel diodes

    SciTech Connect (OSTI)

    Krishnamoorthy, Sriram; Nath, Digbijoy N.; Akyol, Fatih; Park, Pil Sung; Esposto, Michele; Rajan, Siddharth [Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio 43210 (United States)

    2010-11-15

    We report on the design and demonstration of polarization-engineered GaN/InGaN/GaN tunnel junction diodes with high current density and low tunneling turn-on voltage. Wentzel-Kramers-Brillouin calculations were used to model and design tunnel junctions with narrow band gap InGaN-based barrier layers. N-polar p-GaN/In{sub 0.33}Ga{sub 0.67}N/n-GaN heterostructure tunnel diodes were grown using molecular beam epitaxy. Efficient interband tunneling was achieved close to zero bias with a high current density of 118 A/cm{sup 2} at a reverse bias of 1 V, reaching a maximum current density up to 9.2 kA/cm{sup 2}. These results represent the highest current density reported in III-nitride tunnel junctions and demonstrate the potential of III-nitride tunnel devices for a broad range of optoelectronic and electronic applications.

  6. Microstructural Characterization and Shape Memory Response of Ni-Rich NiTiHf and NiTiZr High Temperature Shape Memory Alloys 

    E-Print Network [OSTI]

    Evirgen, Alper

    2014-08-14

    NiTiHf and NiTiZr high temperature shape memory alloys (HTSMAs) have drawn a great deal of attention as cheaper alternatives to Pt, Pd and Au alloyed NiTi-based HTSMAs while NiTiZr alloys also providing at least 20% weight reduction then its Ni...

  7. GaInNAs laser gain

    SciTech Connect (OSTI)

    CHOW,WENG W.; JONES,ERIC D.; MODINE,NORMAND A.; KURTZ,STEVEN R.; ALLERMAN,ANDREW A.

    2000-05-23

    The optical gain spectra for GaInNAs/GaAs quantum wells are computed using a microscopic laser theory. From these spectra, the peak gain and carrier radiative decay rate as functions of carrier density are determined. These dependences allow the study of the lasing threshold current density of GaInNAs/GaAs quantum well structures.

  8. Advantages of the Blue InGaN/GaN Light-Emitting Diodes with an AlGaN/GaN/AlGaN Quantum Well Structured Electron Blocking Layer

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    ABSTRACT: InGaN/GaN light-emitting diodes (LEDs) with p-(AlGaN/GaN/AlGaN) quantum well structured electron. The proposed QWEBL LED structure, in which a p-GaN QW layer is inserted in the p-AlGaN electron blocking layer the radiative recombination rates across the active region. Consequently, the light output power was enhanced

  9. Red emitting photonic devices using InGaP/InGaAlP material system

    E-Print Network [OSTI]

    Kangude, Yamini

    2005-01-01

    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 ...

  10. Engineering the Martensitic Transformation Hysteresis of Ni-Rich NiTi Alloys 

    E-Print Network [OSTI]

    Franco, Brian Eelan

    2014-12-18

    The shape memory behavior in NiTi alloys can be exploited for a wide variety of applications that require active materials. The application dictates the transformation temperatures and hysteresis of the alloy. NiTi alloys ...

  11. Transformation Induced Fatigue of Ni-Rich NiTi Shape Memory Alloy Actuators 

    E-Print Network [OSTI]

    Schick, Justin Ryan

    2011-02-22

    In this work the transformation induced fatigue of Ni-rich NiTi shape memory alloys (SMAs) was investigated. The aerospace industry is currently considering implementing SMA actuators into new applications. However, before ...

  12. 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; Masson, Denis; Riel, Bruno; Fafard, Simon; Jaouad, Abdelatif; Turala, Artur; Ares, Richard; Aimez, Vincent

    2010-10-14

    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}.

  13. Simultaneous determination of Ni-63 and Ni-59 in radioactive wastes by liquid scintillation spectrometry 

    E-Print Network [OSTI]

    Kim, Esther Miyeun

    1988-01-01

    SIMULTANEOUS DETERMINATION OF Ni-63 AND Ni-59 IN RADIOACTIVE WASTES BY LIQUID SCINTILLATION SPECTROMETRY A Thesis by ESTHER MIYEUN KIM Submitted to the Office of Graduate Studies of Texas AgtM University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE May 1988 Major Subject: Health Physics SIMULTANEOUS DETERMINATION OF Ni-63 AND Ni-59 IN RADIOACTIVE WASTES BY LIQUID SCINTILLATION SPECTROMETRY A Thesis by ESTHER MIYEUN KIM Approved as to style...

  14. ³Ni² Clusterbank Replacement Project | Argonne Leadership Computing...

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

    Ni Clusterbank Replacement Project Event Sponsor: Argonne Leadership Computing Facility Seminar Start Date: Oct 20 2015 - 12:00pm BuildingRoom: Building 241Room D173...

  15. GaAs MOEMS Technology

    SciTech Connect (OSTI)

    SPAHN, OLGA B.; GROSSETETE, GRANT D.; CICH, MICHAEL J.; TIGGES, CHRIS P.; RENO, JOHN L.; PEAKE, GREGORY M.; KLEM, JOHN F.; LEAN, JEN; FULLER, CHARLES T.; BURKHART, JEFF; BAUER, THOMAS; SULLIVAN, CHARLES T.

    2003-03-01

    Many MEMS-based components require optical monitoring techniques using optoelectronic devices for converting mechanical position information into useful electronic signals. While the constituent piece-parts of such hybrid opto-MEMS components can be separately optimized, the resulting component performance, size, ruggedness and cost are substantially compromised due to assembly and packaging limitations. GaAs MOEMS offers the possibility of monolithically integrating high-performance optoelectronics with simple mechanical structures built in very low-stress epitaxial layers with a resulting component performance determined only by GaAs microfabrication technology limitations. GaAs MOEMS implicitly integrates the capability for radiation-hardened optical communications into the MEMS sensor or actuator component, a vital step towards rugged integrated autonomous microsystems that sense, act, and communicate. This project establishes a new foundational technology that monolithically combines GaAs optoelectronics with simple mechanics. Critical process issues addressed include selectivity, electrochemical characteristics, and anisotropy of the release chemistry, and post-release drying and coating processes. Several types of devices incorporating this novel technology are demonstrated.

  16. Intense terahertz emission from molecular beam epitaxy-grown GaAs/GaSb(001)

    SciTech Connect (OSTI)

    Sadia, Cyril P.; Laganapan, Aleena Maria; Agatha Tumanguil, Mae; Estacio, Elmer; Somintac, Armando; Salvador, Arnel; Que, Christopher T.; Yamamoto, Kohji; Tani, Masahiko

    2012-12-15

    Intense terahertz (THz) electromagnetic wave emission was observed in undoped GaAs thin films deposited on (100) n-GaSb substrates via molecular beam epitaxy. GaAs/n-GaSb heterostructures were found to be viable THz sources having signal amplitude 75% that of bulk p-InAs. The GaAs films were grown by interruption method during the growth initiation and using various metamorphic buffer layers. Reciprocal space maps revealed that the GaAs epilayers are tensile relaxed. Defects at the i-GaAs/n-GaSb interface were confirmed by scanning electron microscope images. Band calculations were performed to infer the depletion region and electric field at the i-GaAs/n-GaSb and the air-GaAs interfaces. However, the resulting band calculations were found to be insufficient to explain the THz emission. The enhanced THz emission is currently attributed to a piezoelectric field induced by incoherent strain and defects.

  17. Magnetic structure near the Co/NiO(001) interface

    E-Print Network [OSTI]

    Arenholz, Elke

    2008-01-01

    are perpendicular to the NiO moments, hence demonstrating2+ L 3,2 XA spectra and NiO domain pattern (inset). SpectraThe 100 directions of the NiO(001) plane and the orientation

  18. Giant Quadrupole-Resonance in Ni Isotopes 

    E-Print Network [OSTI]

    Youngblood, David H.; Lui, YW; Garg, U.; Peterson, R. J.

    1992-01-01

    VOLUME 45, NUMBER 5 MAY 1992 Giant quadrupole resonance in Ni isotopes D. H. Youngblood and Y.-%. Lui Texas A&M UniUersity, College Station, Texas 77843 U. Garg University of Notre Dame, South Bend, Indiana 46556 R. J. Peterson University... (%) 58+12 76+14 78+14 90+16 Cp 0.80+0.04 0.84+0.04 0.82+0. 12 1.05+0. 10 2174 YOUNGBLOOD, LUI, GARG, AND PETERSON 45 1000 100 60Ni(n, n') E = 129 MeV 1 000 100 58Ni(n, n') 10 10 100 z' 1000 64Ni(n, n') 1OO~y 64 Ni 100 10 I s & & I...

  19. Computational analysis of thin film InGaAs/GaAs quantum well solar cells with

    E-Print Network [OSTI]

    Yu, Edward T.

    Computational analysis of thin film InGaAs/GaAs quantum well solar cells with back side light, Austin, TX 78758, USA * ety@ece.utexas.edu Abstract: Simulations of thin film (~2.5 µm thick) InGaAs/GaAs. Roberts, G. Hill, and C. Calder, "Progress in quantum well solar cells," Thin Solid Films 511­512, 76

  20. GaSb/GaAs type II quantum dot solar cells for enhanced infrared spectral response

    E-Print Network [OSTI]

    Jalali. Bahram

    into existing multijunction cells either as a means to increase the current or efficiency by using low band gapGaSb/GaAs type II quantum dot solar cells for enhanced infrared spectral response R. B infrared spectral response of GaAs-based solar cells that incorporate type II GaSb quantum dots QDs formed

  1. Acoustic assisted actuation of Ni-Mn-Ga ferromagnetic shape memory alloys

    E-Print Network [OSTI]

    Peterson, Bradley William

    2006-01-01

    Ferromagnetic shape memory alloys (FSMA) have been shown in recent work to exhibit large magnetic field induced strains. The material generally requires a large threshold field (of order 3-4 kOe) to initiate the strain. ...

  2. Structure and magnetic properties of Ce?(Ni/Al/Ga)??-A new phase...

    Office of Scientific and Technical Information (OSTI)

    Technial Information About OSTI Mission Organization Chart Achievements Alliances OSTI History Feedback DOE STI Program Scientific and Technical Information Program (STIP)...

  3. Materials Data on Ga2NiO4 (SG:74) by Materials Project

    SciTech Connect (OSTI)

    Kristin Persson

    2014-11-02

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  4. Structure and magnetic properties of Ce?(Ni/Al/Ga)??-A...

    Office of Scientific and Technical Information (OSTI)

    Z 2) with a 436.38(14), b 1004.5(3) and c 1293.4(4) pm. This is a standardized unit cell of the previously published LaAl structure type. Wavelength dispersive...

  5. Synthesis and Characterization of NiMnGa Ferromagnetic Shape Memory Alloy Thin Films 

    E-Print Network [OSTI]

    Jetta, Nishitha

    2011-10-21

    is tailored by varying several deposition parameters. Microstructure of the films has been investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Mechanical properties of as-deposited films have been probed using nano...

  6. Materials Data on HoGa4Ni (SG:63) by Materials Project

    DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

    Kristin Persson

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  7. Materials Data on Ga4Ni3 (SG:230) by Materials Project

    DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

    Kristin Persson

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  8. Materials Data on CeGaNi (SG:189) by Materials Project

    DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

    Kristin Persson

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  9. Materials Data on TiGaNi2 (SG:225) by Materials Project

    DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

    Kristin Persson

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  10. Materials Data on Ti4Ga3Ni2 (SG:189) by Materials Project

    DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

    Kristin Persson

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  11. Materials Data on TiGaNi (SG:189) by Materials Project

    DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

    Kristin Persson

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  12. Materials Data on Zn36Ga5Ni8 (SG:215) by Materials Project

    DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

    Kristin Persson

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  13. Structure and magnetic properties of Ce₃(Ni/Al/Ga)₁₁-A new phase

    Office of Scientific and Technical Information (OSTI)

    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 Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefield MunicipalTechnicalInformation FederatedInformation What'sfunction (Journal Article) | DOEwith

  14. 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.

    2005-11-01

    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.

  15. Enthalpy of mixing of liquid Ni-Zr and Cu-Ni-Zr alloys

    SciTech Connect (OSTI)

    Witusiewicz, V.T.; Sommer, F.

    2000-04-01

    Since the Al-Cu-Ni-Zr system is a basis for the production of bulk amorphous materials by rapid solidification techniques from the liquid state, it is of great scientific interest to determine the partial and the integral thermodynamic functions of liquid and undercooled liquid alloys. Such data, as was pointed out previously, are important in order to understand their extremely good glass-forming ability in multicomponent metallic systems as well as for processing improvements. In order to measure the thermodynamic properties of the Al-Cu-Ni-Zr quaternary, it is necessary to have reliable thermochemical data for its constituent canaries and ternaries first. In a series of articles, the authors have reported in detail the thermodynamic properties of liquid Al-Cu, Al-Ni, Cu-Ni, Cu-Zr, Al-Zr, Al-Cu-Ni, and Al-Cu-Zr alloys. This article deals with the direct calorimetric measurements of the partial and the integral enthalpies of mixing of liquid Ni-Zr and Cu-Ni-Zr alloys and the heat capacity of liquid Ni{sub 26}Zr{sub 74}. In a subsequent article, the authors will present similar data for the liquid ternary Al-Ni-Zr and for the liquid quaternary Al-Cu-Ni-Zr alloys.

  16. Patterned Exfoliation of GaAs Based on Masked Helium Implantation and Subsequent Rapid Thermal Annealing

    SciTech Connect (OSTI)

    Woo, H. J.; Choi, H. W.; Kim, G. D.; Hong, W.; Kim, J. K.

    2009-03-10

    A method of patterning single crystal GaAs based on ion implantation induced selective area exfoliation is suggested. Samples were implanted with 200-500 keV helium ions to a fluence range of 2-4x10{sup 16} He{sup +}/cm{sup 2} at room temperature through masks of Ni mesh (40 {mu}m opening) or stainless steel wire (50 {mu}m in diameter), and subsequent rapid thermal annealing at 350-500{open_square} resulted in expulsion of ion beam exposed material. The influences of ion energy, ion fluence, implantation temperature, subsequent annealing conditions (temperature and ramp rate), and mask pattern and its orientation with GaAs lattice on the patterned exfoliation were examined.

  17. Spectromicroscopy study of interfacial Co/NiO(001)

    E-Print Network [OSTI]

    van der Laan, Gerrit

    2011-01-01

    study of interfacial Co/NiO(001) G. van der Laan, 1 N. D.the Co moments. The Ni moments in NiO prefer to be orienteda component of the moments in the NiO collinear to the Co.

  18. InGaAsN/GaAs heterojunction for multi-junction solar cells

    DOE Patents [OSTI]

    Kurtz, Steven R. (Albuquerque, NM); Allerman, Andrew A. (Albuquerque, NM); Klem, John F. (Albuquerque, NM); Jones, Eric D. (Edgewood, NM)

    2001-01-01

    An InGaAsN/GaAs semiconductor p-n heterojunction is disclosed for use in forming a 0.95-1.2 eV bandgap photodetector with application for use in high-efficiency multi-junction solar cells. The InGaAsN/GaAs p-n heterojunction is formed by epitaxially growing on a gallium arsenide (GaAs) or germanium (Ge) substrate an n-type indium gallium arsenide nitride (InGaAsN) layer having a semiconductor alloy composition In.sub.x Ga.sub.1-x As.sub.1-y N.sub.y with 0GaAs layer, with the InGaAsN and GaAs layers being lattice-matched to the substrate. The InGaAsN/GaAs p-n heterojunction can be epitaxially grown by either molecular beam epitaxy (MBE) or metalorganic chemical vapor deposition (MOCVD). The InGaAsN/GaAs p-n heterojunction provides a high open-circuit voltage of up to 0.62 volts and an internal quantum efficiency of >70%.

  19. Band Structure of Strain-Balanced GaAsBi/GaAsN Super-lattices on GaAs

    SciTech Connect (OSTI)

    Hwang, J.; Phillips, J. D.

    2011-05-31

    GaAs alloys with dilute content of Bi and N provide a large reduction in band-gap energy with increasing alloy composition. GaAsBi/GaAsN heterojunctions have a type-II band alignment, where superlattices based on these materials offer a wide range for designing effective band-gap energy by varying superlattice period and alloy composition. The miniband structure and effective band gap for strain-balanced GaAsBi/GaAsN superlattices with effective lattice match to GaAs are calculated for alloy compositions up to 5% Bi and N using the k·p method. The effective band gap for these superlattices is found to vary between 0.89 and 1.32 eV for period thickness ranging from 10 to 100 Å. The joint density of states and optical absorption of a 40/40 Å GaAs0.96Bi0.04/GaAs0.98N0.02 superlattice are reported demonstrating a ground-state transition at 1.005 eV and first excited transition at 1.074 eV. The joint density of states is similar in magnitude to GaAs, while the optical absorption is approximately one order of magnitude lower due to the spatially indirect optical transition in the type-II structure. The GaAsBi/GaAsN system may provide a new material system with lattice match to GaAs in a spectral range of high importance for optoelectronic devices including solar cells, photodetectors, and light emitters.

  20. Layering and temperature-dependent magnetization and anisotropy of naturally produced Ni/NiO multilayers

    SciTech Connect (OSTI)

    Pappas, S. D.; Trachylis, D.; Velgakis, M. J.; Kapaklis, V.; Joensson, P. E.; Papaioannou, E. Th.; Delimitis, A.; Poulopoulos, P.; Fumagalli, P.; Politis, C.

    2012-09-01

    Ni/NiO multilayers were grown by magnetron sputtering at room temperature, with the aid of the natural oxidation procedure. That is, at the end of the deposition of each single Ni layer, air is let to flow into the vacuum chamber through a leak valve. Then, a very thin NiO layer ({approx}1.2 nm) is formed. Simulated x-ray reflectivity patterns reveal that layering is excellent for individual Ni-layer thickness larger than 2.5 nm, which is attributed to the intercalation of amorphous NiO between the polycrystalline Ni layers. The magnetization of the films, measured at temperatures 5-300 K, has almost bulk-like value, whereas the films exhibit a trend to perpendicular magnetic anisotropy (PMA) with an unusual significant positive interface anisotropy contribution, which presents a weak temperature dependence. The power-law behavior of the multilayers indicates a non-negligible contribution of higher order anisotropies in the uniaxial anisotropy. Bloch-law fittings for the temperature dependence of the magnetization in the spin-wave regime show that the magnetization in the multilayers decreases faster as a function of temperature than the one of bulk Ni. Finally, when the individual Ni-layer thickness decreases below 2 nm, the multilayer stacking vanishes, resulting in a dramatic decrease of the interface magnetic anisotropy and consequently in a decrease of the perpendicular magnetic anisotropy.

  1. Magnetism and transport properties of epitaxial Fe-Ga thin films on GaAs(001)

    SciTech Connect (OSTI)

    Duong Anh Tuan; Shin, Yooleemi; Cho, Sunglae; Dang Duc Dung; Vo Thanh Son

    2012-04-01

    Epitaxial Fe-Ga thin films in disordered bcc {alpha}-Fe crystal structure (A2) have been grown on GaAs(001) by molecular beam epitaxy. The saturated magnetization (M{sub S}) decreased from 1371 to 1105 kA/m with increasing Ga concentration from 10.5 to 24.3 % at room temperature. The lattice parameter increased with the increase in Ga content because of the larger atomic radius of Ga atom than that of Fe. The increase in carrier density with Ga content caused in lower resistivity.

  2. Graphene induced remote surface scattering in graphene/AlGaN/GaN heterostructures

    SciTech Connect (OSTI)

    Liu, Xiwen; Li, Dan; Wang, Bobo; Liu, Bin; Chen, Famin; Jin, Guangri; Lu, Yanwu, E-mail: ywlu@bjtu.edu.cn [Department of Physics, Beijing Jiaotong University, Beijing 100044 (China)

    2014-10-20

    The mobilities of single-layer graphene combined with AlGaN/GaN heterostructures on two-dimensional electron gases in graphene/AlGaN/GaN double heterojunction are calculated. The impact of electron density in single-layer graphene is also studied. Remote surface roughness (RSR) and remote interfacial charge (RIC) scatterings are introduced into this heterostructure. The mobilities limited by RSR and RIC are an order of magnitude higher than that of interface roughness and misfit dislocation. This study contributes to designing structures for generation of higher electron mobility in graphene/AlGaN/GaN double heterojunction.

  3. AlGaAsSb/GaSb Distributed Bragg Reflectors Grown by Organometallic Vapor Phase Epitaxy

    SciTech Connect (OSTI)

    C.A. Wang; C.J. Vineis; D.R. Calawa

    2002-02-13

    The first AlGaAsSb/GaSb quarter-wave distributed Bragg reflectors grown by metallic vapor phase epitaxy are reported. The peak reflectance is 96% for a 10-period structure.

  4. Impact of electrochemical process on the degradation mechanisms of AlGaN/GaN HEMTs

    E-Print Network [OSTI]

    Gao, Feng, Ph. D. Massachusetts Institute of Technology

    2014-01-01

    AlGaN/GaN high electron mobility transistors (HEMTs) constitute a new generation of transistors with excellent electrical characteristics and great potential to replace silicon technology in the future, especially in high ...

  5. Rare-earth chromium gallides RE{sub 4}CrGa{sub 12} (RE=Tb-Tm)

    SciTech Connect (OSTI)

    Slater, Brianna R.; Bie, Haiying; Stoyko, Stanislav S. [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada)] [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada); Bauer, Eric D.; Thompson, Joe D. [Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)] [Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Mar, Arthur, E-mail: arthur.mar@ualberta.ca [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada)] [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada)

    2012-12-15

    The ternary rare-earth-metal chromium gallides RE{sub 4}CrGa{sub 12} (RE=Tb-Tm) have been prepared by reactions of the elements at 1000 Degree-Sign C in the presence of excess gallium used as a self-flux. Their structures are derived by inserting Cr atoms into a quarter of the empty Ga{sub 6} octahedral clusters found in the parent binary gallides REGa{sub 3} (AuCu{sub 3}-type), although single-crystal X-ray diffraction studies suggest that complex superstructures may be adopted. An ideal ordered Y{sub 4}PdGa{sub 12}-type structure was successfully refined for a crystal of Dy{sub 4}CrGa{sub 12} (Pearson symbol cI34, space group Im3{sup Macron }m, Z=2, a=8.572(1) A). Magnetic measurements on single-crystal samples reveal ferromagnetic or possibly ferrimagnetic ordering for the Tb, Dy, and Er members (T{sub C}=22, 15, and 2.8 K, respectively) and antiferromagnetic ordering for the Ho member (T{sub N}=7.5 K). Band structure calculations on a hypothetical 'Y{sub 4}CrGa{sub 12}' model suggest that the Cr atoms carry no local magnetic moment. - Graphical abstract: RE{sub 4}CrGa{sub 12} is derived by inserting Cr atoms into empty Ga{sub 6} octahedral clusters present in the parent binary gallides REGa{sub 3}. Highlights: Black-Right-Pointing-Pointer RE{sub 4}MGa{sub 12} (previously known for M=Fe, Ni, Pd, Pt, Ag) has been extended to M=Cr. Black-Right-Pointing-Pointer RE{sub 4}CrGa{sub 12} compounds show predominantly ferromagnetic ordering. Black-Right-Pointing-Pointer Band structure calculations suggest that Cr atoms carry no local magnetic moment.

  6. GaN nanowires show more 3D piezoelectricity than bulk GaN

    E-Print Network [OSTI]

    Espinosa, Horacio D.

    director cds murder nudity soundtrack BBC movie releases footage worth documentary film Blu-rays Blu-ray Ga

  7. GaInP/GaAs/GaInAs Monolithic Tandem Cells for High-Performance Solar Concentrators

    SciTech Connect (OSTI)

    Wanlass, M. W.; Ahrenkiel, S. P.; Albin, D. S.; Carapella, J. J.; Duda, A.; Emery, K.; Geisz, J. F.; Jones, K.; Kurtz, S.; Moriarty, T.; Romero, M. J.

    2005-08-01

    We present a new approach for ultra-high-performance tandem solar cells that involves inverted epitaxial growth and ultra-thin device processing. The additional degree of freedom afforded by the inverted design allows the monolithic integration of high-, and medium-bandgap, lattice-matched (LM) subcell materials with lower-bandgap, lattice-mismatched (LMM) materials in a tandem structure through the use of transparent compositionally graded layers. The current work concerns an inverted, series-connected, triple-bandgap, GaInP (LM, 1.87 eV)/GaAs (LM, 1.42 eV)/GaInAs (LMM, {approx}1 eV) device structure grown on a GaAs substrate. Ultra-thin tandem devices are fabricated by mounting the epiwafers to pre-metallized Si wafer handles and selectively removing the parent GaAs substrate. The resulting handle-mounted, ultra-thin tandem cells have a number of important advantages, including improved performance and potential reclamation/reuse of the parent substrate for epitaxial growth. Additionally, realistic performance modeling calculations suggest that terrestrial concentrator efficiencies in the range of 40-45% are possible with this new tandem cell approach. A laboratory-scale (0.24 cm2), prototype GaInP/GaAs/GaInAs tandem cell with a terrestrial concentrator efficiency of 37.9% at a low concentration ratio (10.1 suns) is described, which surpasses the previous world efficiency record of 37.3%.

  8. Fig. 1. Magnetic hysteresis of NiO-doped NiF2 conversion materials

    E-Print Network [OSTI]

    Siegel, Paul H.

    member with CMRR, is leading her group to design, optimize and develop new materials for energy storage materials for higher energy lithium ion batteries (at least double the energy density of today's technologyFig. 1. Magnetic hysteresis of NiO-doped NiF2 conversion materials CMRR Newsletter Shirley Meng

  9. Electronic circuits having NiAl and Ni.sub.3 Al substrates

    DOE Patents [OSTI]

    Deevi, Seetharama C. (Midlothian, VA); Sikka, Vinod K. (Oak Ridge, TN)

    1999-01-01

    An electronic circuit component having improved mechanical properties and thermal conductivity comprises NiAl and/or Ni.sub.3 Al, upon which an alumina layer is formed prior to applying the conductive elements. Additional layers of copper-aluminum alloy or copper further improve mechanical strength and thermal conductivity.

  10. Antiproton Production in Ni+ni Collisions at 1.85 Gev/nucleon 

    E-Print Network [OSTI]

    LI, GQ; Ko, Che Ming.

    1994-01-01

    Antiproton production in Ni+Ni collisions at 1.85 GeV/nucleon is studied in the relativistic Vlasov-Uehling-Uhlenbeck model. The self-energies of the antiproton are determined from the nucleon self-energies by the G-parity transformation. Also...

  11. Spontaneous emission in GaN/InGaN photonic crystal nanopillars

    E-Print Network [OSTI]

    Boyer, Edmond

    . Sigalas, "InGaN/GaN quantum-well heterostructure light-emitting diodes employing photonic crystal, "III-nitride blue and ultraviolet photonic crystal light emitting diodes," Appl. Phys. Lett. 84, 466, and H. Benisty, "Photonic-crystal GaN light-emitting diodes with tailored guided modes distribution

  12. Switchable piezoelectric transduction in AlGaN/GaN MEMS resonators

    E-Print Network [OSTI]

    Weinstein, Dana

    This work presents a new switching mechanism in piezoelectric transduction of AlGaN/GaN bulk acoustic resonators. A piezoelectric transducer is formed in the AlGaN, between a top Schottky electrode and a 2D electron gas ...

  13. Photosensitivity of the Ni-A state of [NiFe] hydrogenase from Desulfovibrio vulgaris Miyazaki F with visible light

    SciTech Connect (OSTI)

    Osuka, Hisao; Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5, Takayama-cho, Ikoma-shi, Nara 630-0192 ; Shomura, Yasuhito; Komori, Hirofumi; Shibata, Naoki; Nagao, Satoshi; Higuchi, Yoshiki; CREST, JST, Gobancho, Chiyoda-ku, Tokyo 102-0076 ; Hirota, Shun; CREST, JST, Gobancho, Chiyoda-ku, Tokyo 102-0076

    2013-01-04

    Highlights: Black-Right-Pointing-Pointer Ni-A state of [NiFe] hydrogenase showed light sensitivity. Black-Right-Pointing-Pointer New FT-IR bands were observed with light irradiation of the Ni-A state. Black-Right-Pointing-Pointer EPR g-values of the Ni-A state shifted upon light irradiation. Black-Right-Pointing-Pointer The light-induced state converted back to the Ni-A state under the dark condition. -- Abstract: [NiFe] hydrogenase catalyzes reversible oxidation of molecular hydrogen. Its active site is constructed of a hetero dinuclear Ni-Fe complex, and the oxidation state of the Ni ion changes according to the redox state of the enzyme. We found that the Ni-A state (an inactive unready, oxidized state) of [NiFe] hydrogenase from Desulfovibrio vulgaris Miyazaki F (DvMF) is light sensitive and forms a new state (Ni-AL) with irradiation of visible light. The Fourier transform infrared (FT-IR) bands at 1956, 2084 and 2094 cm{sup -1} of the Ni-A state shifted to 1971, 2086 and 2098 cm{sup -1} in the Ni-AL state. The g-values of g{sub x} = 2.30, g{sub y} = 2.23 and g{sub z} = 2.01 for the signals in the electron paramagnetic resonance (EPR) spectrum of the Ni-A state at room temperature varied for -0.009, +0.012 and +0.010, respectively, upon light irradiation. The light-induced Ni-AL state converted back immediately to the Ni-A state under dark condition at room temperature. These results show that the coordination structure of the Fe site of the Ni-A state of [NiFe] hydrogenase is perturbed significantly by light irradiation with relatively small coordination change at the Ni site.

  14. Scientific Achievement Networks of highly photoresponsive crystalline GaSe

    E-Print Network [OSTI]

    Geohegan, David B.

    Scientific Achievement Networks of highly photoresponsive crystalline GaSe nanosheets a crystalline GaSe target was adjusted to directly grow networks of interconnected triangular GaSe crystalline nanosheets of ~ 200 nm size (inset shows atomic

  15. Preparation of PtNi Nanoparticles for the Electrocatalytic Oxidation of Methanol

    E-Print Network [OSTI]

    Deivaraj, T.C.

    Carbon supported PtNi nanoparticles were prepared by hydrazine reduction of Pt and Ni precursor salts under different conditions, namely by conventional heating (PtNi-1), by prolonged reaction at room temperature (PtNi-2) ...

  16. Carbon Nanotube Growth Using Ni Catalyst in Different Layouts

    E-Print Network [OSTI]

    Nguyen, H. Q.

    Vertically aligned carbon nanotubes have been grown using Ni as catalyst by plasma enhanced chemical vapor deposition system (PECVD) in various pre-patterned substrates. Ni was thermally evaporated on silicon substrates ...

  17. Development of metallization for GaAs and AlGaAs concentrator solar cells

    SciTech Connect (OSTI)

    Tobin, S.P.

    1987-04-01

    A three-layer metallization system was developed for high temperature stability on GaAs and AlGaAs solar cells. The layers are a Pt ohmic contact metal that forms thermally stable compounds with GaAs, a TiN diffusion barrier, and a gold conductor. The solar cell structure was also designed for contact stability, with the key component being a heavily doped GaAs cap layer. Reactively sputtered TiN was found to act as an excellent barrier when deposited under the proper conditions. The conditions were carefully optimized for low resistivity and low stress in the films. A low but nonzero substrate bias during sputtering was found to be important. Solar cells with sputtered metallizations of Pt/TiN/Ti/Pt/Au were found to be thermally stable up to 500/sup 0/C for 15 minutes in vacuum. At 600/sup 0/C there was catastrophic degradation of the cells due to dissociation of uncapped GaAs surfaces. Below this temperature the metallization performed as designed. The Pt and GaAs layers reacted to form a stable PtGa compound layer that gave low contact resistance. There was no penetration of Au or GaAs through the barrier layer. These results are a very encouraging first step leading to stable, reliable GaAs and AlGaAs concentrator cells.

  18. Oxygen Adsorption on Au–Ni(111) Surface Alloys

    E-Print Network [OSTI]

    Lee, Jae-Gook

    Molecular O[subscript 2] dissociates upon interaction with a Ni(111) surface, as the spatial and energetic overlap between the Ni 3d electrons and the O[subscript 2] antibonding orbitals is quite favorable. On a Au–Ni(111) ...

  19. High Temperature coatings based on {beta}-NiAI

    SciTech Connect (OSTI)

    Severs, Kevin

    2012-07-10

    High temperature alloys are reviewed, focusing on current superalloys and their coatings. The synthesis, characerization, and oxidation performance of a NiAl–TiB{sub 2} composite are explained. A novel coating process for Mo–Ni–Al alloys for improved oxidation performance is examined. The cyclic oxidation performance of coated and uncoated Mo–Ni–Al alloys is discussed.

  20. Structural and optical properties of InGaN–GaN nanowire heterostructures grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Limbach, F.; Gotschke, T.; Stoica, T.; Calarco, R.; Sutter, E.; Ciston, J.; Cusco, R.; Artus, L.; Kremling, S.; Ho?fling, S.; Worschech, L.; Gru?tzmacher, D.

    2011-01-01

    InGaN/GaN nanowire (NW) heterostructures grown by plasma assisted molecular beam epitaxy were studied in comparison to their GaN and InGaN counterparts. The InGaN/GaN heterostructure NWs are composed of a GaN NW, a thin InGaN shell, and a multifaceted InGaN cap wrapping the top part of the GaN NW. High-resolution transmission electron microscopy (HRTEM) images taken from different parts of a InGaN/GaN NW show a wurtzite structure of the GaN core and the epitaxial InGaN shell around it, while additional crystallographic domains are observed whithin the InGaN cap region. Large changes in the lattice parameter along the wire, from pure GaN to higher In concentration demonstrate the successful growth of a complex InGaN/GaN NW heterostructure. Photoluminescence (PL) spectra of these heterostructure NW ensembles show rather broad and intense emission peak at 2.1 eV. However, ?-PL spectra measured on single NWs reveal a reduced broadening of the visible luminescence. The analysis of the longitudinal optical phonon Raman peak position and its shape reveal a variation in the In content between 20% and 30%, in agreement with the values estimated by PL and HRTEM investigations. The reported studies are important for understanding of the growth and properties of NW heterostructures suitable for applications in optoelectronics and photovoltaics.

  1. Giant monopole strength in Ni-58 

    E-Print Network [OSTI]

    Lui, YW; Clark, HL; Youngblood, David H.

    2000-01-01

    The strength distribution of the giant monopole resonance in Ni-58 has been measured from E-x = 10 to 35 MeV using small-angle scattering of 240-MeV alpha particles. E0 strength corresponding to 74(-12)(+22)% of the E0 EWSR was found between E-x...

  2. Ohmic contacts to n-GaSb 

    E-Print Network [OSTI]

    Yang, Zhengchong

    1997-01-01

    In recent years, the Ill-V semiconductor GaSb and its ternary alloys containing antimony have exhibited interesting electrical and optical properties for device applications which include negative resistance tunnel devices, lasers, detectors and FET...

  3. A Ni/surface-modified Diamond Composite Electroplating Coating on Superelastic NiTi Alloy as Potential Dental Bur Design

    E-Print Network [OSTI]

    Zheng, Yufeng

    A Ni/surface-modified Diamond Composite Electroplating Coating on Superelastic NiTi Alloy: Composite Electroplating; Surface-modified Diamond Particles; Interfacial Adhesion; NiTi alloy; Dental Bur into nickel coating, and its shank made of stainless steel. There are strong demands from the dentist

  4. Rare-earth transition-metal gallium chalcogenides RE{sub 3}MGaCh{sub 7} (M=Fe, Co, Ni; Ch=S, Se)

    SciTech Connect (OSTI)

    Rudyk, Brent W.; Stoyko, Stanislav S.; Oliynyk, Anton O.; Mar, Arthur, E-mail: arthur.mar@ualberta.ca

    2014-02-15

    Six series of quaternary rare-earth transition-metal chalcogenides RE{sub 3}MGaCh{sub 7} (M=Fe, Co, Ni; Ch=S, Se), comprising 33 compounds in total, have been prepared by reactions of the elements at 1050 °C (for the sulphides) or 900 °C (for the selenides). They adopt noncentrosymmetric hexagonal structures (ordered Ce{sub 3}Al{sub 1.67}S{sub 7}-type, space group P6{sub 3}, Z=2) with cell parameters in the ranges of a=9.5–10.2 Å and c=6.0–6.1 Å for the sulphides and a=10.0–10.5 Å and c=6.3–6.4 Å for the selenides as refined from powder X-ray diffraction data. Single-crystal structures were determined for five members of the sulphide series RE{sub 3}FeGaS{sub 7} (RE=La, Pr, Tb) and RE{sub 3}CoGaS{sub 7} (RE=La, Tb). The highly anisotropic crystal structures consist of one-dimensional chains of M-centred face-sharing octahedra and stacks of Ga-centred tetrahedra all pointing in the same direction. Magnetic measurements on the sulphides reveal paramagnetic behaviour in some cases and long-range antiferromagnetic behaviour with low Néel temperatures (15 K or lower) in others. Ga L-edge XANES spectra support the presence of highly cationic Ga tetrahedral centres with a tendency towards more covalent Ga–Ch character on proceeding from the sulphides to the selenides. Band structure calculations on La{sub 3}FeGaS{sub 7} indicate that the electronic structure is dominated by Fe 3d-based states near the Fermi level. - Graphical abstract: The series of chalcogenides RE{sub 3}MGaS{sub 7}, which form for a wide range of rare-earth and transition metals (M=Fe, Co, Ni), adopt highly anisotropic structures containing chains of M-centred octahedra and stacks of Ga-centred tetrahedra. Display Omitted - Highlights: • Six series (comprising 33 compounds) of chalcogenides RE{sub 3}MGaCh{sub 7} were prepared. • They adopt noncentrosymmetric hexagonal structures with high anisotropy. • Most compounds are paramagnetic; some show antiferromagnetic ordering. • Ga L-edge XANES confirms presence of cationic Ga species.

  5. GaTe semiconductor for radiation detection

    DOE Patents [OSTI]

    Payne, Stephen A. (Castro Valley, CA); Burger, Arnold (Nashville, TN); Mandal, Krishna C. (Ashland, MA)

    2009-06-23

    GaTe semiconductor is used as a room-temperature radiation detector. GaTe has useful properties for radiation detectors: ideal bandgap, favorable mobilities, low melting point (no evaporation), non-hygroscopic nature, and availability of high-purity starting materials. The detector can be used, e.g., for detection of illicit nuclear weapons and radiological dispersed devices at ports of entry, in cities, and off shore and for determination of medical isotopes present in a patient.

  6. In Situ XAS of Ni-W Hydrocracking Catalysts

    SciTech Connect (OSTI)

    Yang, N. [Argonne National Laboratory, Argonne, IL 60439 (United States); Mickelson, G. E.; Greenlay, N.; Bare, Simon R. [UOP LLC, Des Plaines, IL 60016 (United States); Kelly, S. D. [EXAFS Analysis, Bolingbrook, IL 60440 (United States)

    2007-02-02

    Ni-W based catalysts are very attractive in hydrotreating of heavy oil due to their high hydrogenation activity. In the present research, two catalyst samples, prepared by different methods, that exhibit significant differences in activity were sulfided in situ, and the local structure of the Ni and W were studied using X-ray absorption spectroscopy (XAS). The Ni XANES spectra were analyzed using a linear component fitting, and the EXAFS spectra of the WS2 platelets in the sulfided catalysts were modeled. The Ni and W are fully sulfided in the higher activity sample, and there are both unsulfided Ni ({approx}25%) and W (<10%) in the lower activity sample.

  7. Ga, Ca, and 3d transition element (Cr through Zn) partitioning among spinel-lherzolite phases from the Lanzo massif, Italy: Analytical results and crystal chemistry

    SciTech Connect (OSTI)

    Wogelius, R.A.; Fraser, D.G.

    1994-06-01

    Ultramafic rocks exposed in Lanzo massif, Italy is a record of mantle geochemistry, melting, sub-solidus re-equilibration. Plagioclase(+ spinel)-lherzolite samples were analyzed by Scanning Proton Microscopy, other techniques. Previous work postulated partial melting events and a two-stage sub-solidus cooling history; this paper notes Ga enrichment on spinel-clinopyroxene grain boundaries, high Ga and transition element content of spinel, and pyroxene zonation in Ca and Al. Trace element levels in olivine and orthopyroxene are also presented. Zoning trends are interpreted as due to diffusion during cooling. Olivine-clinopyroxene Cr and Ca exchange as well as clinopyroxene and spinel zonation trends indicate that the massif experienced at least two sub-solidus cooling episodes, one at 20 kbar to 1000 C and one at 8 kbar <750C. Ga levels in cores of Lanzo high-Cr spinels are high (82-66 ppM) relative to other mantle spinels (66-40 ppM), indicating enrichment. Ga content of ultramafic spinels apparently increases with Cr content; this may be due to: increased Ga solubility stemming from crystal chemical effects and/or higher Ga activities in associated silicate melts. Thus, during melting, high-Cr residual spinel may tend to buffer solid-phase Ga level. These spinels are not only rich in Ga and Cr (max 26.37 el. wt %), but also in Fe (max 21.07 el. wt %), Mn (max 3400 ppM), and Zn (max 2430 ppM). These enrichments are again due to melt extraction and partitioning into spinel structure. Low Ni (min 1050 ppM) levels are due to unsuccessful competition of Ni with Cr for octahedral structural sites caused by crystal field. Comparisons of change in partitioning vs Cr content among several 3d transition elements for spinels from Lanzo, other localities allow us to separate crystal field effects from bulk chemical effects and to show that in typical assemblages, inversion of olivine-spinel partition coefficient for Ni from <1 to >1 should occur at 11% el. wt. Cr in spinel.

  8. Temperature-induced martensite in magnetic shape memory Fe{sub 2}MnGa observed by photoemission electron microscopy

    SciTech Connect (OSTI)

    Jenkins, Catherine; Scholl, Andreas; Kainuma, R.; Elmers, Hans-Joachim; Omori, Toshihiro

    2012-01-18

    The magnetic domain structure in single crystals of a Heusler shape memory compound near the composition Fe{sub 2}MnGa was observed during phase transition by photoelectron emission microscopy at Beamline 11.0.1.1 of the Advanced Light Source. The behavior is comparable with recent observations of an adaptive martensite phase in prototype Ni{sub 2}MnGa, although the pinning in the recent work is an epitaxial interface and in this work the e#11;ective pinning plane is a boundary between martensitic variants that transform in a self-accommodating way from the single crystal austenite phase present at high temperatures. Temperature dependent observations of the twinning structure give information as to the coupling behavior between the magnetism and the structural evolution.

  9. InGaN/GaN tunnel junctions for hole injection in GaN light emitting diodes

    SciTech Connect (OSTI)

    Krishnamoorthy, Sriram, E-mail: krishnamoorthy.13@osu.edu, E-mail: rajan@ece.osu.edu; Akyol, Fatih [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Rajan, Siddharth, E-mail: krishnamoorthy.13@osu.edu, E-mail: rajan@ece.osu.edu [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

    2014-10-06

    InGaN/GaN tunnel junction contacts were grown using plasma assisted molecular beam epitaxy (MBE) on top of a metal-organic chemical vapor deposition (MOCVD)-grown InGaN/GaN blue (450?nm) light emitting diode. A voltage drop of 5.3?V at 100?mA, forward resistance of 2 × 10{sup ?2} ? cm{sup 2}, and a higher light output power compared to the reference light emitting diodes (LED) with semi-transparent p-contacts were measured in the tunnel junction LED (TJLED). A forward resistance of 5?×?10{sup ?4} ? cm{sup 2} was measured in a GaN PN junction with the identical tunnel junction contact as the TJLED, grown completely by MBE. The depletion region due to the impurities at the regrowth interface between the MBE tunnel junction and the MOCVD-grown LED was hence found to limit the forward resistance measured in the TJLED.

  10. Journal of Crystal Growth 298 (2007) 272275 Dislocation analysis in homoepitaxial GaInN/GaN light emitting

    E-Print Network [OSTI]

    Wetzel, Christian M.

    2007-01-01

    of GaInN/GaN-based light emitting diodes (LED) on quasi-bulk GaN with an atomically flat polished were much improved. The optical output power of the light emitting diode increased by more than one. Cathodoluminescence; A1. Threading dislocation density; A2. Homoepitaxial growth; B1. GaInN; B3. Light emitting diode

  11. Thermoelectric effects in wurtzite GaN and AlxGa1-xN alloys and Alexander A. Balandin

    E-Print Network [OSTI]

    Thermoelectric effects in wurtzite GaN and AlxGa1-xN alloys Weili Liua and Alexander A. Balandin have investigated theoretically the thermoelectric effects in wurtzite GaN crystals and AlxGa1-xN-based alloys may have some potential as thermoelectric materials at high temperature. It was found

  12. 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)

    2013-03-04

    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.

  13. Green cubic GaInN/GaN light-emitting diode on microstructured silicon (100)

    SciTech Connect (OSTI)

    Stark, Christoph J. M.; Detchprohm, Theeradetch; Wetzel, Christian, E-mail: wetzel@ieee.org [Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States) [Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Future Chips Constellation, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180 (United States); Lee, S. C.; Brueck, S. R. J. [Department of Electrical and Computer Engineering and Center for High Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, New Mexico 87106 (United States)] [Department of Electrical and Computer Engineering and Center for High Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, New Mexico 87106 (United States); Jiang, Y.-B. [Department of Earth and Planetary Science, University of New Mexico, Albuquerque, New Mexico 87131 (United States)] [Department of Earth and Planetary Science, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

    2013-12-02

    GaInN/GaN light-emitting diodes free of piezoelectric polarization were prepared on standard electronic-grade Si(100) substrates. Micro-stripes of GaN and GaInN/GaN quantum wells in the cubic crystal structure were grown on intersecting (111) planes of microscale V-grooved Si in metal-organic vapor phase epitaxy, covering over 50% of the wafer surface area. Crystal phases were identified in electron back-scattering diffraction. A cross-sectional analysis reveals a cubic structure virtually free of line defects. Electroluminescence over 20 to 100??A is found fixed at 487?nm (peak), 516?nm (dominant). Such structures therefore should allow higher efficiency, wavelength-stable light emitters throughout the visible spectrum.

  14. A hole accelerator for InGaN/GaN light-emitting diodes

    SciTech Connect (OSTI)

    Zhang, Zi-Hui; Liu, Wei; Tan, Swee Tiam; Ji, Yun; Wang, Liancheng; Zhu, Binbin; Zhang, Yiping; Lu, Shunpeng; Zhang, Xueliang; Hasanov, Namig; Sun, Xiao Wei, E-mail: EXWSUN@ntu.edu.sg, E-mail: VOLKAN@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Demir, Hilmi Volkan, E-mail: EXWSUN@ntu.edu.sg, E-mail: VOLKAN@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Department of Electrical and Electronics, Department of Physics, and UNAM-Institute of Material Science and Nanotechnology, Bilkent University, TR-06800 Ankara (Turkey)

    2014-10-13

    The quantum efficiency of InGaN/GaN light-emitting diodes (LEDs) has been significantly limited by the insufficient hole injection, and this is caused by the inefficient p-type doping and the low hole mobility. The low hole mobility makes the holes less energetic, which hinders the hole injection into the multiple quantum wells (MQWs) especially when a p-type AlGaN electron blocking layer (EBL) is adopted. In this work, we report a hole accelerator to accelerate the holes so that the holes can obtain adequate kinetic energy, travel across the p-type EBL, and then enter the MQWs more efficiently and smoothly. In addition to the numerical study, the effectiveness of the hole accelerator is experimentally shown through achieving improved optical output power and reduced efficiency droop for the proposed InGaN/GaN LED.

  15. 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)

    2014-09-21

    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?=0.53(×2.1±1) cm² s?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.

  16. NiW and NiRu Bimetallic Catalysts for Ethylene Steam Reforming: Alternative Mechanisms for Sulfur Resistance

    SciTech Connect (OSTI)

    Rangan, M.; Yung, M. M.; Medlin, J. W.

    2012-06-01

    Previous investigations of Ni-based catalysts for the steam reforming of hydrocarbons have indicated that the addition of a second metal can reduce the effects of sulfur poisoning. Two systems that have previously shown promise for such applications, NiW and NiRu, are considered here for the steam reforming of ethylene, a key component of biomass derived tars. Monometallic and bimetallic Al{sub 2}O{sub 3}-supported Ni and W catalysts were employed for ethylene steam reforming in the presence and absence of sulfur. The NiW catalysts were less active than Ni in the absence of sulfur, but were more active in the presence of 50 ppm H{sub 2}S. The mechanism for the W-induced improvements in sulfur resistance appears to be different from that for Ru in NiRu. To probe reasons for the sulfur resistance of NiRu, the adsorption of S and C{sub 2}H{sub 4} on several bimetallic NiRu alloy surfaces ranging from 11 to 33 % Ru was studied using density functional theory (DFT). The DFT studies reveal that sulfur adsorption is generally favored on hollow sites containing Ru. Ethylene preferentially adsorbs atop the Ru atom in all the NiRu (111) alloys investigated. By comparing trends across the various bimetallic models considered, sulfur adsorption was observed to be correlated with the density of occupied states near the Fermi level while C{sub 2}H{sub 4} adsorption was correlated with the number of unoccupied states in the d-band. The diverging mechanisms for S and C{sub 2}H{sub 4} adsorption allow for bimetallic surfaces such as NiRu that enhance ethylene binding without accompanying increases in sulfur binding energy. In contrast, bimetallics such as NiSn and NiW appear to decrease the affinity of the surface for both the reagent and the poison.

  17. GaN: Defect and Device Issues

    SciTech Connect (OSTI)

    Pearton, S.J.; Ren, F.; Shul, R.J.; Zolper, J.C.

    1998-11-09

    The role of extended and point defects, and key impurities such as C, O and H, on the electrical and optical properties of GaN is reviewed. Recent progress in the development of high reliability contacts, thermal processing, dry and wet etching techniques, implantation doping and isolation and gate insulator technology is detailed. Finally, the performance of GaN-based electronic and photonic devices such as field effect transistors, UV detectors, laser diodes and light-emitting diodes is covered, along with the influence of process-induced or grown-in defects and impurities on the device physics.

  18. Influence of pressure on photoluminescence and electroluminescence in GaN/InGaN/AlGaN quantum wells

    E-Print Network [OSTI]

    Weinstein, Benard.A.

    recently that the temperature shifts of the photo- and electroluminescence EL peak energies in Nichia greenV/GPa for the green and blue diodes, respectively. The observed pressure coefficients are much lower than those characteristic of the energy gap in GaN ( 40 meV/GPa) or the energy gap in InN ( 33 meV/GPa). This kind

  19. Microstructures in rapidly solidified Ni-Mo alloys

    SciTech Connect (OSTI)

    Jayaraman, N.; Tewari, S.N.; Hemker, K.J.; Glasgow, T.K.

    1985-01-01

    Ni-Mo alloys of compositions ranging from pure Ni to Ni-40 at % Mo were rapidly solidified by chill block melt spinning in vacuum and were examined by optical metallography, x-ray diffraction and transmission electron microscopy. Rapid solidification resulted in an extension of molybdenum solubility in nickel from 28 to 37.5 at %. A number of different phases and microstructures were seen at different depths (solidification conditions) from the quenched surface of the melt spun ribbons.

  20. InGaAs/GaAs quantum dot interdiffiusion induced by cap layer overgrowth

    SciTech Connect (OSTI)

    Jasinski, J.; Babinski, A.; Czeczott, M.; Bozek, R.

    2000-06-28

    The effect of thermal treatment during and after growth of InGaAs/GaAs quantum dot (QD) structures was studied. Transmission electron microscopy and atomic force microscopy confirmed the presence of interacting QDs, as was expected from analysis of temperature dependence of QD photoluminescence (PL) peak. The results indicate that the effect of post-growth annealing can be similar to the effect of elevated temperature of capping layer growth. Both, these thermal treatments can lead to a similar In and Ga interdiffiusion resulting in a similar blue-shift of QD PL peak.

  1. Optical spectroscopy of quantum confined states in GaAs/AlGaAs quantum well tubes

    SciTech Connect (OSTI)

    Shi, Teng; Fickenscher, Melodie; Smith, Leigh; Jackson, Howard; Yarrison-Rice, Jan; Gao, Qiang; Tan, Hoe; Jagadish, Chennupati; Etheridge, Joanne; Wong, Bryan M.

    2013-12-04

    We have investigated the quantum confinement of electronic states in GaAs/Al{sub x}Ga{sub 1?x}As nanowire heterostructures which contain radial GaAs quantum wells of either 4nm or 8nm. Photoluminescence and photoluminescence excitation spectroscopy are performed on single nanowires. We observed emission and excitation of electron and hole confined states. Numerical calculations of the quantum confined states using the detailed structural information on the quantum well tubes show excellent agreement with these optical results.

  2. Oxidation-resistant, solution-processed plasmonic Ni nanochain...

    Office of Scientific and Technical Information (OSTI)

    solution-processed plasmonic Ni nanochain-SiOsub x (x < 2) selective solar thermal absorbers Citation Details In-Document Search Title: Oxidation-resistant,...

  3. Fusion of radioactive $^{132}$Sn with $^{64}$Ni

    E-Print Network [OSTI]

    J. F. Liang; D. Shapira; J. R. Beene; C. J. Gross; R. L. Varner; A. Galindo-Uribarri; J. Gomez del Campo; P. A. Hausladen; P. E. Mueller; D. W. Stracener; H. Amro; J. J. Kolata; J. D. Bierman; A. L. Caraley; K. L. Jones; Y. Larochelle; W. Loveland; D. Peterson

    2007-04-05

    Evaporation residue and fission cross sections of radioactive $^{132}$Sn on $^{64}$Ni were measured near the Coulomb barrier. A large sub-barrier fusion enhancement was observed. Coupled-channel calculations including inelastic excitation of the projectile and target, and neutron transfer are in good agreement with the measured fusion excitation function. When the change in nuclear size and shift in barrier height are accounted for, there is no extra fusion enhancement in $^{132}$Sn+$^{64}$Ni with respect to stable Sn+$^{64}$Ni. A systematic comparison of evaporation residue cross sections for the fusion of even $^{112-124}$Sn and $^{132}$Sn with $^{64}$Ni is presented.

  4. The combustion synthesis of Ni-Ti shape memory alloys

    SciTech Connect (OSTI)

    Moore, J.J.; Yi, H.C. (Colorado School of Mines, Golden (USA))

    1990-08-01

    Combustion synthesis of Ni-Ti-series shape-memory alloys yields both time and energy savings over conventional production methods. The solidified combustion synthesis process products have been cold-rolled into plates which exhibit the shape-memory effect, and it was noted that shape-memory transition temperatures may be tailored over a -78 to 460 C temperature range through the substitution of a third element for Ni; this element may be Pd or Fe. Accounts are given of the experimental combustion syntheses of Ni-Ti-Fe and Ti-Ni-Pd. 24 refs.

  5. Structural and optical properties of InGaN–GaN nanowire heterostructures grown by molecular beam epitaxy

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

    Limbach, F.; Gotschke, T.; Stoica, T.; Calarco, R.; Sutter, E.; Ciston, J.; Cusco, R.; Artus, L.; Kremling, S.; Ho?fling, S.; et al

    2011-01-01

    InGaN/GaN nanowire (NW) heterostructures grown by plasma assisted molecular beam epitaxy were studied in comparison to their GaN and InGaN counterparts. The InGaN/GaN heterostructure NWs are composed of a GaN NW, a thin InGaN shell, and a multifaceted InGaN cap wrapping the top part of the GaN NW. High-resolution transmission electron microscopy (HRTEM) images taken from different parts of a InGaN/GaN NW show a wurtzite structure of the GaN core and the epitaxial InGaN shell around it, while additional crystallographic domains are observed whithin the InGaN cap region. Large changes in the lattice parameter along the wire, from pure GaNmore »to higher In concentration demonstrate the successful growth of a complex InGaN/GaN NW heterostructure. Photoluminescence (PL) spectra of these heterostructure NW ensembles show rather broad and intense emission peak at 2.1 eV. However, ?-PL spectra measured on single NWs reveal a reduced broadening of the visible luminescence. The analysis of the longitudinal optical phonon Raman peak position and its shape reveal a variation in the In content between 20% and 30%, in agreement with the values estimated by PL and HRTEM investigations. The reported studies are important for understanding of the growth and properties of NW heterostructures suitable for applications in optoelectronics and photovoltaics.« less

  6. IEEE Energy2030 Atlanta, GA USA

    E-Print Network [OSTI]

    Gross, George

    of an aggregation of battery vehicles for the provision of frequency regulation ­ requiring very fast response timesIEEE Energy2030 Atlanta, GA USA 17-18 November, 2008 Design of a Conceptual Framework for the V2G in common is the batteries, which provide good storage capacity that can be effectively integrated

  7. 495 Tech Way NW Atlanta, GA 30318

    E-Print Network [OSTI]

    Li, Mo

    495 Tech Way NW Atlanta, GA 30318 404.385.0384 comments@energy.gatech.edu Copyright 2014 · Georgia concerns, low-cost, clean, secure energy solutions will be necessary to address our global energy needs and sustain our way of life. Georgia Tech Energy Innovations The Strategic Energy Institute's scientists

  8. Defect studies in low-temperature-grown GaAs

    SciTech Connect (OSTI)

    Bliss, D.E.

    1992-11-01

    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.

  9. Electron mobility enhancement in AlN/GaN/AlN heterostructures with InGaN nanogrooves

    E-Print Network [OSTI]

    it was discovered by Davydov et al.1 and con- firmed by independent studies2,3 that its band gap is small, EG InN =0 The conduction band offset at GaN/AlN interface was estimated as EQW=0.7 EG AlN -EG GaN =1918 meV. The nanoN/GaN/AlN QW. The depth of the nanogroove is calculated as E0=0.8 EG GaN -EG InxGa1-xN . The band gap of InxGa1

  10. Enhanced photocatalytic efficiency in zirconia buffered n-NiO/p-NiO single crystalline heterostructures by nanosecond laser treatment

    SciTech Connect (OSTI)

    Molaei, R.; Bayati, M. R.; Alipour, H. M.; Nori, S.; Narayan, J.

    2013-06-21

    We report the formation of NiO based single crystalline p-n junctions with enhanced photocatalytic activity induced by pulsed laser irradiation. The NiO epilayers were grown on Si(001) substrates buffered with cubic yttria-stabilized zirconia (c-YSZ) by using pulsed laser deposition. The NiO/c-YSZ/Si heterostructures were subsequently laser treated by 5 pulses of KrF excimer laser (pulse duration = 25 Multiplication-Sign 10{sup -9} s) at lower energies. Microstructural studies, conducted by X-ray diffraction ({theta}-2{theta} and {phi} techniques) and high resolution transmission electron microscope, showed a cube-on-cube epitaxial relationship at the c-YSZ/Si interface; the epitaxial relationship across the NiO/c-YSZ interface was established as NiO<111 > Double-Vertical-Line Double-Vertical-Line c-YSZ<001> and in-plane NiO<110> Double-Vertical-Line Double-Vertical-Line c-YSZ<100>. Electron microscopy studies showed that the interface between the laser annealed and the pristine region as well as the NiO/c-YSZ interface was atomically sharp and crystallographically continuous. The formation of point defects, namely oxygen vacancies and NiO, due to the coupling of the laser photons with the NiO epilayers was confirmed by XPS. The p-type electrical characteristics of the pristine NiO epilayers turned to an n-type behavior and the electrical conductivity was increased by one order of magnitude after laser treatment. Photocatalytic activity of the pristine (p-NiO/c-YSZ/Si) and the laser-annealed (n-NiO/p-NiO/c-YSZ/Si) heterostructures were assessed by measuring the decomposition rate of 4-chlorophenol under UV light. The photocatalytic reaction rate constants were determined to be 0.0059 and 0.0092 min{sup -1} for the as-deposited and the laser-treated samples, respectively. The enhanced photocatalytic efficiency was attributed to the suppressed charge carrier recombination in the NiO based p-n junctions and higher electrical conductivity. Besides, the oxygen vacancies ease the adsorption of 4-chlorophenol, hydroxyl, and water molecules to the surface. Thus, n-NiO/p-NiO single crystalline catalysts can be introduced as a potent candidate to remediate the environmental pollution.

  11. Energies of Electronic States of Ni (II) Ion in NiO-Al2O3 Catalyst Prepared by Impregnation

    SciTech Connect (OSTI)

    Obadovic, D. Z.; Kiurski, J.; Marinkovic-Neducin, R. P.

    2007-04-23

    The behavior of NiO-Al2O3 catalysts is strongly dependent on the preparation method, as well as on pretreatment conditions. In the present work we investigated the influences of Ni(II) ion on NiO-Al2O3 catalysts properties due to the preparation by impregnation method. Based on experimental diffuse reflectance spectroscopy (DRS) data of electronic d-d transitions of Ni (II) promoter ion the energies of electronic states in spinel-like structure were calculated, and the most probable scheme of molecular orbital have been proposed.

  12. Development and Industrialization of InGaN/GaN LEDs on Patterned...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    epitaxial growth of indium gallium nitride (InGaN) layers capable of producing high-efficiency LEDs when combined with chip-on-board packaging techniques. The proposed...

  13. High-field quasi-ballistic transport in AlGaN/GaN heterostructures

    SciTech Connect (OSTI)

    Danilchenko, B. A.; Tripachko, N. A.; Belyaev, A. E.; Vitusevich, S. A. Hardtdegen, H.; Lüth, H.

    2014-02-17

    Mechanisms of electron transport formation in 2D conducting channels of AlGaN/GaN heterostructures in extremely high electric fields at 4.2?K have been studied. Devices with a narrow constriction for the current flow demonstrate high-speed electron transport with an electron velocity of 6.8?×?10{sup 7}?cm/s. Such a velocity is more than two times higher than values reported for conventional semiconductors and about 15% smaller than the limit value predicted for GaN. Superior velocity is attained in the channel with considerable carrier reduction. The effect is related to a carrier runaway phenomenon. The results are in good agreement with theoretical predictions for GaN-based materials.

  14. 2DEG electrodes for piezoelectric transduction of AlGaN/GaN MEMS resonators

    E-Print Network [OSTI]

    Weinstein, Dana

    A 2D electron gas (2DEG) interdigitated transducer (IDT) in Gallium Nitride (GaN) resonators is introduced and demonstrated. This metal-free transduction does not suffer from the loss mechanisms associated with more commonly ...

  15. Emission and Excitation Spectra of ZnO:Ga and ZnO:Ga,N Ceramics

    E-Print Network [OSTI]

    P. A. Rodnyi; I. V. Khodyuk; E. I. Gorokhova; S. B. Mikhrin; P. Dorenbos

    2010-09-07

    The spectral characteristics of ZnO:Ga and ZnO:Ga,N ceramics prepared by uniaxial hot pressing have been investigated. At room temperature, the edge (exciton) band at 3.12 eV dominates in the luminescence spectra of ZnO:Ga, while a wide luminescence band at 2.37 eV, which is likely to be due to zinc vacancies, is observed in the spectra of ZnO:Ga,N. Upon heating, the edge band maximum shifts to lower energies and the bandwidth increases. The extrapolated position of the edge-band maximum at zero temperature, Em(0) = 3.367 +/- 0.005 eV, is in agreement with the data for thin zinc oxide films. The luminescence excitation spectra in the range from 3 to 6.5 eV are reported and the mechanism of energy transfer to excitons and luminescence centers is considered.

  16. Composition profiling of GaAs/AlGaAs quantum dots grown by droplet epitaxy

    SciTech Connect (OSTI)

    Bocquel, J.; Koenraad, P. M. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Giddings, A. D.; Prosa, T. J.; Larson, D. J. [CAMECA Instruments, Inc., 5500 Nobel Drive, Madison, Wisconsin 53711 (United States); Mano, T. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

    2014-10-13

    Droplet epitaxy (DE) is a growth method which can create III-V quantum dots (QDs) whose optoelectronic properties can be accurately controlled through the crystallisation conditions. In this work, GaAs/AlGaAs DE-QDs have been analyzed with the complimentary techniques of cross-sectional scanning tunneling microscopy and atom probe tomography. Structural details and a quantitative chemical analysis of QDs of different sizes are obtained. Most QDs were found to be pure GaAs, while a small proportion exhibited high intermixing caused by a local etching process. Large QDs with a high aspect ratio were observed to have an Al-rich crown above the GaAs QD. This structure is attributed to differences in mobility of the cations during the capping phase of the DE growth.

  17. SF 6432-NI (04-95)

    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: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity ofkandz-cm11 Outreach Home RoomPreservation of Fe(II) byMultidayAlumni > The EnergyRyanPhysics6/14/11 Page 1 of6432-NI

  18. Ni(II) Salts and 2-Propanol Effect Catalytic Reductive Coupling of Epoxides and Alkynes

    E-Print Network [OSTI]

    Beaver, Matthew G.

    A Ni-catalyzed reductive coupling of alkynes and epoxides using Ni(II) salts and simple alcohol reducing agents is described. Whereas previously reported conditions relied on Ni(cod)2 and Et3B, this system has several ...

  19. Continuous spin reorientation transition in epitaxially grown antiferromagnetic NiO thin films

    E-Print Network [OSTI]

    Li, J.

    2011-01-01

    along certain crystal axis [e.g. , NiO(100)]. Thusthe r 2 p S z 2, NiO ( dMgO ) / S NiO should be an approximation in the small limit.

  20. Solution-based thermodynamic modeling of the Ni-Al-Mo system...

    Office of Scientific and Technical Information (OSTI)

    (Al,Mo,Ni)0.75(Al,Mo,Ni)0.25. Thus, -fcc and -Ni3Al are modeled with a single Gibbs free energy function with appropriate treatment of the chemical ordering contribution. In...

  1. On strongly GA-convex functions and stochastic processes

    SciTech Connect (OSTI)

    Bekar, Nurgül Okur; Akdemir, Hande Günay; ??can, ?mdat

    2014-08-20

    In this study, we introduce strongly GA-convex functions and stochastic processes. We provide related well-known Kuhn type results and Hermite-Hadamard type inequality for strongly GA-convex functions and stochastic processes.

  2. InGaAs/GaAs (110) quantum dot formation via step meandering

    SciTech Connect (OSTI)

    Diez-Merino, Laura; Tejedor, Paloma

    2011-07-01

    InGaAs (110) semiconductor quantum dots (QDs) offer very promising prospects as a material base for a new generation of high-speed spintronic devices, such as single electron transistors for quantum computing. However, the spontaneous formation of InGaAs QDs is prevented by two-dimensional (2D) layer-by-layer growth on singular GaAs (110) substrates. In this work we have studied, by using atomic force microscopy and photoluminescence spectroscopy (PL), the growth of InGaAs/GaAs QDs on GaAs (110) stepped substrates by molecular beam epitaxy (MBE), and the modification of the adatom incorporation kinetics to surface steps in the presence of chemisorbed atomic hydrogen. The as-grown QDs exhibit lateral dimensions below 100 nm and emission peaks in the 1.35-1.37 eV range. It has been found that a step meandering instability derived from the preferential attachment of In adatoms to [110]-step edges relative to [11n]-type steps plays a key role in the destabilization of 2D growth that leads to 3D mound formation on both conventional and H-terminated vicinal substrates. In the latter case, the driving force for 3D growth via step meandering is enhanced by H-induced upward mass transport in addition to the lower energy cost associated with island formation on H-terminated substrates, which results in a high density array of InGaAs/GaAs dots selectively nucleated on the terrace apices with reduced lateral dimensions and improved PL efficiency relative to those of conventional MBE-grown samples.

  3. Sheet resistance under Ohmic contacts to AlGaN/GaN heterostructures

    SciTech Connect (OSTI)

    Haj?asz, M., E-mail: m.hajlasz@m2i.nl [Materials innovation institute (M2i), Mekelweg 2, 2628 CD, Delft (Netherlands); MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE, Enschede (Netherlands); Donkers, J. J. T. M.; Sque, S. J.; Heil, S. B. S. [NXP Semiconductors Research, High Tech Campus 46, 5656 AE, Eindhoven (Netherlands); Gravesteijn, D. J. [NXP Semiconductors Research, High Tech Campus 46, 5656 AE, Eindhoven (Netherlands); MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE, Enschede (Netherlands); Rietveld, F. J. R. [NXP Semiconductors, Gerstweg 2, 6534 AE, Nijmegen (Netherlands); Schmitz, J. [MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE, Enschede (Netherlands)

    2014-06-16

    For the determination of specific contact resistance in semiconductor devices, it is usually assumed that the sheet resistance under the contact is identical to that between the contacts. This generally does not hold for contacts to AlGaN/GaN structures, where an effective doping under the contact is thought to come from reactions between the contact metals and the AlGaN/GaN. As a consequence, conventional extraction of the specific contact resistance and transfer length leads to erroneous results. In this Letter, the sheet resistance under gold-free Ti/Al-based Ohmic contacts to AlGaN/GaN heterostructures on Si substrates has been investigated by means of electrical measurements, transmission electron microscopy, and technology computer-aided design simulations. It was found to be significantly lower than that outside of the contact area; temperature-dependent electrical characterization showed that it exhibits semiconductor-like behavior. The increase in conduction is attributed to n-type activity of nitrogen vacancies in the AlGaN. They are thought to form during rapid thermal annealing of the metal stack when Ti extracts nitrogen from the underlying semiconductor. The high n-type doping in the region between the metal and the 2-dimensional electron gas pulls the conduction band towards the Fermi level and enhances horizontal electron transport in the AlGaN. Using this improved understanding of the properties of the material underneath the contact, accurate values of transfer length and specific contact resistance have been extracted.

  4. AlGaAs/GaAs photovoltaic converters for high power narrowband radiation

    SciTech Connect (OSTI)

    Khvostikov, Vladimir; Kalyuzhnyy, Nikolay; Mintairov, Sergey; Potapovich, Nataliia; Shvarts, Maxim; Sorokina, Svetlana; Andreev, Viacheslav; Luque, Antonio

    2014-09-26

    AlGaAs/GaAs-based laser power PV converters intended for operation with high-power (up to 100 W/cm{sup 2}) radiation were fabricated by LPE and MOCVD techniques. Monochromatic (? = 809 nm) conversion efficiency up to 60% was measured at cells with back surface field and low (x = 0.2) Al concentration 'window'. Modules with a voltage of 4 V and the efficiency of 56% were designed and fabricated.

  5. Guided Neuronal Growth on Arrays of Biofunctionalized GaAs/InGaAs Semiconductor Microtubes

    E-Print Network [OSTI]

    Cornelius S. Bausch; Aune Koitmäe; Eric Stava; Amanda Price; Pedro J. Resto; Yu Huang; David Sonnenberg; Yuliya Stark; Christian Heyn; Justin C. Williams; Erik W. Dent; Robert H. Blick

    2013-05-06

    We demonstrate embedded growth of cortical mouse neurons in dense arrays of semiconductor microtubes. The microtubes, fabricated from a strained GaAs/InGaAs heterostructure, guide axon growth through them and enable electrical and optical probing of propagating action potentials. The coaxial nature of the microtubes -- similar to myelin -- is expected to enhance the signal transduction along the axon. We present a technique of suppressing arsenic toxicity and prove the success of this technique by overgrowing neuronal mouse cells.

  6. Lateral and Vertical Transistors Using the AlGaN/GaN Heterostructure

    SciTech Connect (OSTI)

    Chowdhury, S; Mishra, UK

    2013-10-01

    Power conversion losses are endemic in all areas of electricity consumption, including motion control, lighting, air conditioning, and information technology. Si, the workhorse of the industry, has reached its material limits. Increasingly, the lateral AlGaN/GaN HEMT based on gallium nitride (GaN-on-Si) is becoming the device of choice for medium power electronics as it enables high-power conversion efficiency and reduced form factor at attractive pricing for wide market penetration. The reduced form factor enabled by high-efficiency operation at high frequency further enables significant system price reduction because of savings in bulky extensive passive elements and heat sink costs. The high-power market, however, still remains unaddressed by lateral GaN devices. The current and voltage demand for high power conversion application makes the chip area in a lateral topology so large that it becomes more difficult to manufacture. Vertical GaN devices would play a big role alongside of silicon carbide (SiC) to address the high power conversion needs. In this paper, the development, performance, and status of lateral and vertical GaN devices are discussed.

  7. GaNPAs Solar Cells Lattice-Matched To GaP: Preprint

    SciTech Connect (OSTI)

    Geisz, J. F.; Friedman, D. J.; Kurtz, S.

    2002-05-01

    This conference paper describes the III-V semiconductors grown on silicon substrates are very attractive for lower-cost, high-efficiency multijunction solar cells, but lattice-mismatched alloys that result in high dislocation densities have been unable to achieve satisfactory performance. GaNxP1-x-yAsy is a direct-gap III-V alloy that can be grown lattice-matched to Si when y= 4.7x - 0.1. We propose the use of lattice-matched GaNPAs on silicon for high-efficiency multijunction solar cells. We have grown GaNxP1-x-yAsy on GaP (with a similar lattice constant to silicon) by metal-organic chemical vapor phase epitaxy with direct band-gaps in the range of 1.5 to 2.0 eV. We demonstrate the performance of single-junction GaNxP1-x-yAsy solar cells grown on GaP substrates and discuss the prospects for the development of monolithic high-efficiency multijunction solar cells based on silicon substrates.

  8. Accurate characterization and improvement of GaAs microstrip attenuation 

    E-Print Network [OSTI]

    Carroll, James Mason

    1992-01-01

    Convergence. III. E. 6 Final Model. III. F Simulation Results for 100 um GaAs. . III. F. 1 On-GaAs Microstrip. III. I', 2 Suspended Microstrip Line . . . . 50 . . . . 51 . . . . 54 . . . . 56 . . . . 56 . . . 56 . . . . 64 64 . . . , 64 III. F. 3... Comparison Between On-GaAs and Suspcndcd Microstrip . . . 68 III. F. 4 Microstrip Inductance III. G EM Parameters in CAD Simulations . . III. H Simulation Results for 150 um GaAs. III. I Conclusions and Recommendations. IV RESEARCH ACCOMPLISHMENTS...

  9. Advanced technologies for improving high frequency performance of AlGaN/GaN high electron mobility transistors

    E-Print Network [OSTI]

    Chung, Jinwook W. (Jinwook Will)

    2008-01-01

    In this thesis, we have used a combination of physical analysis, numerical simulation and experimental work to identify and overcome some of the main challenges in AlGaN/GaN high electron mobility transistors (HEMTs) for ...

  10. Synthesis and electrochemical properties of NiO nanospindles

    SciTech Connect (OSTI)

    Zhou, Hai; Lv, Baoliang; Xu, Yao; Wu, Dong

    2014-02-01

    Graphical abstract: NiO nanospindles with a different electrochemical activity as compared to those previous reports were synthesized via an agglomeration–dissolution–recrystallization growth process without the addition of any surfactant. - Highlights: • NiO nanospindles were synthesized without the addition of any surfactant. • The agglomeration–dissolution–recrystallization growth process was used to explain the precursors’ formation process of the spindle-like NiO. • As-obtained spindle-like NiO showed a different electrochemical activity as compared to those previous reports. - Abstract: NiO nanospindles were successfully synthesized via a hydrothermal and post-treatment method. The as-synthesized nanospindles were about several hundred nanometers in width and about one micrometer in length. X-ray diffraction (XRD) analysis revealed that the spindle-like structure was cubic NiO phase crystalline. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) analysis indicated that these NiO nanospindles were of single crystal nature. On the basis of time-dependent experiments, a possible agglomeration–dissolution–recrystallization growth process was proposed to explain the formation process of the spindle-like precursors. The cyclic voltammetry (CV) measurement showed that the as-prepared spindle-like NiO exhibited a pseudo-capacitance behavior.

  11. Lanthanide Al-Ni base Ericsson cycle magnetic refrigerants

    DOE Patents [OSTI]

    Gschneidner, K.A. Jr.; Takeya, Hiroyuki

    1995-10-31

    A magnetic refrigerant for a magnetic refrigerator using the Ericsson thermodynamic cycle comprises DyAlNi and (Gd{sub 0.54}Er{sub 0.46})AlNi alloys having a relatively constant {Delta}Tmc over a wide temperature range. 16 figs.

  12. Luminescence properties of the hybrid Si-Ni nanoparticles system

    E-Print Network [OSTI]

    Lalayan, A A; Movsesyan, H A

    2015-01-01

    The luminescence properties of the colloidal hybrid Si - Ni nanoparticles system fabricated in the pure water by pulsed laser ablation is considered. The red-shifted photoluminescence of this system because of the Stark effect in the Coulomb field of the charged Ni nanoparticles has been registered in the blue range of the spectrum.

  13. A New Combustion Synthesis Method for GaN:Eu3+ and Ga2O3 :Eu3+

    E-Print Network [OSTI]

    McKittrick, Joanna

    A New Combustion Synthesis Method for GaN:Eu3+ and Ga2O3 :Eu3+ Luminescent Powders G. A. Hirata1 between the precursors. The preparation of Eu-doped Ga2O3 powders was achieved using a new combustion)3 and Ga(NO3)3 as the precursors and hydrazine as (non-carbonaceous) fuel. A spontaneous combustion

  14. In situ XAS of Ni-W hydrocracking catalysts.

    SciTech Connect (OSTI)

    Yang, N.; Mickelson, G. E.; Greenlay, N.; Kelly, S. D.; Bare, S. R.; UOP LLC; EXAFS Analysis

    2007-01-01

    Ni-W based catalysts are very attractive in hydrotreating of heavy oil due to their high hydrogenation activity. In the present research, two catalyst samples, prepared by different methods, that exhibit significant differences in activity were sulfided in situ, and the local structure of the Ni and W were studied using X-ray absorption spectroscopy (XAS). The Ni XANES spectra were analyzed using a linear component fitting, and the EXAFS spectra of the WS{sub 2} platelets in the sulfided catalysts were modeled. The Ni and W are fully sulfided in the higher activity sample, and there are both unsulfided Ni ({approx}25%) and W (<10%) in the lower activity sample.

  15. Hydrides of CeNi/sub 5/, MmNi/sub 5/, Ca/sub 0/ /sub 2/(Ce/sub 0/ /sub 65/Mm/sub 0/ /sub 35/)/sub 0/ /sub 8/Ni/sub 5/, Ca/sub 0/ /sub 2/Ce/sub 0/ /sub 8/Ni/sub 5/, Ca/sub 0/ /sub 2/Mm/sub 0/ /sub 8/Ni/sub 5/, and mixed CeNi/sub 5//MmNi/sub 5/

    SciTech Connect (OSTI)

    Lakner, J.F.; Chow, T.S.

    1982-09-01

    Six intermetallic alloys (CeNi/sub 5/, MmNi/sub 5/, Ca/sub 0/ /sub 2/(Ce/sub 0/ /sub 65/Mm/sub 0/ /sub 35/)/sub 0/ /sub 8/Ni/sub 5/, Ca/sub 0/ /sub 2/Ce/sub 0/ /sub 8/Ni/sub 5/, Ca/sub 0/ /sub 2/Mm/sub 0/ /sub 8/Ni/sub 5/, and a mixed alloy, CeNi/sub 5//MmNi/sub 5/) were investigated with respect to their suitability to provide high hydrogen capacity and their potential for use in providing substantial hydrogen pressure at both low and high temperatures. A second phase of our investigation dealt with ball-milling and hydriding and dehydriding cycles to produce fine particles for use in hydride powder transfer studies. A summary of several Van't Hoff plots is also included for hydride-forming alloys.

  16. Improved device performance of InAs/GaAs quantum dot solar cells with GaP strain compensation layers

    E-Print Network [OSTI]

    Jalali. Bahram

    Improved device performance of InAs/GaAs quantum dot solar cells with GaP strain compensation Center for High Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, New Mexico optical, electrical, and spectral response characteristics of three-stack InAs/GaAs quantum dot solar

  17. Lattice-Mismatched GaAs/InGaAs Two-Junction Solar Cells by Direct Wafer Bonding

    SciTech Connect (OSTI)

    Tanabe, K.; Aiken, D. J.; Wanlass, M. W.; Morral, A. F.; Atwater, H. A.

    2006-01-01

    Direct bonded interconnect between subcells of a lattice-mismatched III-V compound multijunction cell would enable dislocation-free active regions by confining the defect network needed for lattice mismatch accommodation to tunnel junction interfaces, while metamorphic growth inevitably results in less design flexibility and lower material quality than is desirable. The first direct-bond interconnected multijunction solar cell, a two-terminal monolithic GaAs/InGaAs two-junction solar cell, is reported and demonstrates viability of direct wafer bonding for solar cell applications. The tandem cell open-circuit voltage was approximately the sum of the subcell open-circuit voltages. This achievement shows direct bonding enables us to construct lattice-mismatched III-V multijunction solar cells and is extensible to an ultrahigh efficiency InGaP/GaAs/InGaAsP/InGaAs four-junction cell by bonding a GaAs-based lattice-matched InGaP/GaAs subcell and an InP-based lattice-matched InGaAsP/InGaAs subcell. The interfacial resistance experimentally obtained for bonded GaAs/InP smaller than 0.10 Ohm-cm{sup 2} would result in a negligible decrease in overall cell efficiency of {approx}0.02%, under 1-sun illumination.

  18. Effects of Cr and Ni on Interdiffusion and Reaction between U and Fe-Cr-Ni Alloys

    SciTech Connect (OSTI)

    K. Huang; Y. Park; L. Zhou; K.R. Coffey; Y.H. Sohn; B.H. Sencer; J. R. Kennedy

    2014-08-01

    Metallic U-alloy fuel cladded in steel has been examined for high temperature fast reactor technology wherein the fuel cladding chemical interaction is a challenge that requires a fundamental and quantitative understanding. In order to study the fundamental diffusional interactions between U with Fe and the alloying effect of Cr and Ni, solid-to-solid diffusion couples were assembled between pure U and Fe, Fe–15 wt.%Cr or Fe–15 wt.%Cr–15 wt.%Ni alloy, and annealed at high temperature ranging from 580 to 700 °C. The microstructures and concentration profiles that developed from the diffusion anneal were examined by scanning electron microscopy, and X-ray energy dispersive spectroscopy (XEDS), respectively. Thick U6Fe and thin UFe2 phases were observed to develop with solubilities: up to 2.5 at.% Ni in U6(Fe,Ni), up to 20 at.%Cr in U(Fe, Cr)2, and up to 7 at.%Cr and 14 at.% Ni in U(Fe, Cr, Ni)2. The interdiffusion and reactions in the U vs. Fe and U vs. Fe–Cr–Ni exhibited a similar temperature dependence, while the U vs. Fe–Cr diffusion couples, without the presence of Ni, yielded greater activation energy for the growth of intermetallic phases – lower growth rate at lower temperature but higher growth rate at higher temperature.

  19. Properties of (Ga,Mn)As codoped with Li

    SciTech Connect (OSTI)

    Miyakozawa, Shohei; Chen, Lin; Matsukura, Fumihiro; Ohno, Hideo

    2014-06-02

    We grow Li codoped (Ga,Mn)As layers with nominal Mn composition up to 0.15 by molecular beam epitaxy. The layers before and after annealing are characterized by x-ray diffraction, transport, magnetization, and ferromagnetic resonance measurements. The codoping with Li reduces the lattice constant and electrical resistivity of (Ga,Mn)As after annealing. We find that (Ga,Mn)As:Li takes similar Curie temperature to that of (Ga,Mn)As, but with pronounced magnetic moments and in-plane magnetic anisotropy, indicating that the Li codoping has nontrivial effects on the magnetic properties of (Ga,Mn)As.

  20. 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.

    solar cells are triple-junction concentrator devices, with each junction efficiently col- lecting subcell in a multijunction de- vice. GaAs0.66 P0.34 single-junction solar cells with Eg = 1.83 eV were56 IEEE JOURNAL OF PHOTOVOLTAICS, VOL. 2, NO. 1, JANUARY 2012 Metamorphic GaAsP and InGaP Solar

  1. Delocalization and hybridization enhance the magnetocaloric effect in Ni2Mn0.75Cu0.25Ga

    E-Print Network [OSTI]

    Roy, Sujoy

    2008-01-01

    USA Manuel Lujan Neutron Scattering Center, Los Alamosof the Manuel Lujan Neutron Scattering Center, Los Alamosthe use of the Lujan Neutron Scattering Center at LANSCE,

  2. A dislocation model for the magnetic field induced shape memory effect in Ni2MnGa

    E-Print Network [OSTI]

    Ferreira, Paulo J.

    , such as Nitinol. In addition, MSM alloys can easily respond at over 50 times greater fre- quencies (250 Hz) than

  3. Reactive codoping of GaAlInP compound semiconductors

    DOE Patents [OSTI]

    Hanna, Mark Cooper (Boulder, CO); Reedy, Robert (Golden, CO)

    2008-02-12

    A GaAlInP compound semiconductor and a method of producing a GaAlInP compound semiconductor are provided. The apparatus and method comprises a GaAs crystal substrate in a metal organic vapor deposition reactor. Al, Ga, In vapors are prepared by thermally decomposing organometallic compounds. P vapors are prepared by thermally decomposing phospine gas, group II vapors are prepared by thermally decomposing an organometallic group IIA or IIB compound. Group VIB vapors are prepared by thermally decomposing a gaseous compound of group VIB. The Al, Ga, In, P, group II, and group VIB vapors grow a GaAlInP crystal doped with group IIA or IIB and group VIB elements on the substrate wherein the group IIA or IIB and a group VIB vapors produced a codoped GaAlInP compound semiconductor with a group IIA or IIB element serving as a p-type dopant having low group II atomic diffusion.

  4. Three-junction solar cells comprised of a thin-film GaInP/GaAs tandem cell mechanically stacked on a Si cell

    SciTech Connect (OSTI)

    Yazawa, Y.; Tamura, K.; Watahiki, S.; Kitatani, T.; Ohtsuka, H.; Warabisako, T.

    1997-12-31

    Three-junction tandem solar cells were fabricated by mechanical stacking of a thin-film GaInP/GaAs monolithic tandem cell and a Si cell. The epitaxial lift-off (ELO) technique was used for the thinning of GaInP/GaAs tandem cells. Both spectral responses of the GaInP top cell and the GaAs middle cell in the thin-film GaInP/GaAs monolithic tandem cell were conserved. The Si cell performance has been improved by reducing the absorption loss in the GaAs substrate.

  5. Chemical beam epitaxy growth of AlGaAs/GaAs tunnel junctions using trimethyl aluminium for multijunction solar cells

    SciTech Connect (OSTI)

    Paquette, B.; DeVita, M.; Turala, A.; Kolhatkar, G.; Boucherif, A.; Jaouad, A.; Aimez, V.; Arès, R.; Wilkins, M.; Wheeldon, J. F.; Walker, A. W.; Hinzer, K.; Fafard, S.

    2013-09-27

    AlGaAs/GaAs tunnel junctions for use in high concentration multijunction solar cells were designed and grown by chemical beam epitaxy (CBE) using trimethyl aluminium (TMA) as the p-dopant source for the AlGaAs active layer. Controlled hole concentration up to 4?10{sup 20} cm{sup ?3} was achieved through variation in growth parameters. Fabricated tunnel junctions have a peak tunneling current up to 6140 A/cm{sup 2}. These are suitable for high concentration use and outperform GaAs/GaAs tunnel junctions.

  6. Ni/metal hydride secondary element

    DOE Patents [OSTI]

    Bauerlein, Peter

    2005-04-19

    A Ni/metal hydride secondary element having a positive nickel hydroxide electrode, a negative electrode having a hydrogen storage alloy, and an alkaline electrolyte, the positive electrode, provided with a three-dimensional metallic conductive structure, also contains an aluminum compound which is soluble in the electrolyte, in addition to nickel hydroxide and cobalt oxide. The aluminum compound is aluminum hydroxide and/or aluminum oxide, and the mass of the aluminum compound which is present in the positive bulk material mixture is 0.1 to 2% by weight relative to the mass of the nickel hydroxide which is present. In combination with aluminum hydroxide or aluminum oxide, the positive electrode further contains lanthanoid oxidic compounds Y.sub.2 O.sub.3, La.sub.2 O.sub.3 and Ca(OH).sub.2, as well as mixtures of these compounds.

  7. 0.7-eV GaInAs Junction for a GaInP/GaAs/GaInAs(1eV)/GaInAs(0.7eV) Four-Junction Solar Cell

    SciTech Connect (OSTI)

    Friedman, D. J.; Geisz, J. F.; Norman, A. G.; Wanlass, M. W.; Kurtz, S. R.

    2006-01-01

    We discuss recent developments in III-V multijunction solar cells, focusing on adding a fourth junction to the Ga{sub 0.5}In{sub 0.5} P/GaAs/Ga{sub 0.75}In{sub 0.25}As inverted three-junction cell. This cell, grown inverted on GaAs so that the lattice-mismatched Ga{sub 0.75}In{sub 0.25}As third junction is the last one grown, has demonstrated 38% efficiency, and 40% is likely in the near future. To achieve still further gains, a lower-bandgap Ga{sub x}In{sub 1-x}As fourth junction could be added to the three-junction structure for a four-junction cell whose efficiency could exceed 45% under concentration. Here, we present the initial development of the Ga{sub x}In{sub 1-x}As fourth junction. Junctions of various bandgaps ranging from 0.88 to 0.73 eV were grown, in order to study the effect of the different amounts of lattice mismatch. At a bandgap of 0.88 eV, junctions were obtained with very encouraging {approx}80% quantum efficiency, 57% fill factor, and 0.36 eV open-circuit voltage. The device performance degrades with decreasing bandgap (i.e., increasing lattice mismatch). We model the four-junction device efficiency vs. fourth junction bandgap to show that an 0.7-eV fourth-junction bandgap, while optimal if it could be achieved in practice, is not necessary; an 0.9-eV bandgap would still permit significant gains in multijunction cell efficiency while being easier to achieve than the lower-bandgap junction.

  8. Electron tunneling spectroscopy study of electrically active traps in AlGaN/GaN high electron mobility transistors

    SciTech Connect (OSTI)

    Yang, Jie Cui, Sharon; Ma, T. P.; Hung, Ting-Hsiang; Nath, Digbijoy; Krishnamoorthy, Sriram; Rajan, Siddharth

    2013-11-25

    We investigate the energy levels of electron traps in AlGaN/GaN high electron mobility transistors by the use of electron tunneling spectroscopy. Detailed analysis of a typical spectrum, obtained in a wide gate bias range and with both bias polarities, suggests the existence of electron traps both in the bulk of AlGaN and at the AlGaN/GaN interface. The energy levels of the electron traps have been determined to lie within a 0.5?eV band below the conduction band minimum of AlGaN, and there is strong evidence suggesting that these traps contribute to Frenkel-Poole conduction through the AlGaN barrier.

  9. A InGaN/GaN quantum dot green ({lambda}=524 nm) laser

    SciTech Connect (OSTI)

    Zhang Meng; Banerjee, Animesh; Lee, Chi-Sen; Hinckley, John M.; Bhattacharya, Pallab

    2011-05-30

    The characteristics of self-organized InGaN/GaN quantum dot lasers are reported. The laser heterostructures were grown on c-plane GaN substrates by plasma-assisted molecular beam epitaxy and the laser facets were formed by focused ion beam etching with gallium. Emission above threshold is characterized by a peak at 524 nm (green) and linewidth of 0.7 nm. The lowest measured threshold current density is 1.2 kA/cm{sup 2} at 278 K. The slope and wall plug efficiencies are 0.74 W/A and {approx}1.1%, respectively, at 1.3 kA/cm{sup 2}. The value of T{sub 0}=233 K in the temperature range of 260-300 K.

  10. Photocapacitance study of type-II GaSb/GaAs quantum ring solar cells

    SciTech Connect (OSTI)

    Wagener, M. C.; Botha, J. R.; Carrington, P. J.; Krier, A.

    2014-01-07

    In this study, the density of states associated with the localization of holes in GaSb/GaAs quantum rings are determined by the energy selective charging of the quantum ring distribution. The authors show, using conventional photocapacitance measurements, that the excess charge accumulated within the type-II nanostructures increases with increasing excitation energies for photon energies above 0.9?eV. Optical excitation between the localized hole states and the conduction band is therefore not limited to the ?(k?=?0) point, with pseudo-monochromatic light charging all states lying within the photon energy selected. The energy distribution of the quantum ring states could consequently be accurately related from the excitation dependence of the integrated photocapacitance. The resulting band of localized hole states is shown to be well described by a narrow distribution centered 407?meV above the GaAs valence band maximum.

  11. Efficiency enhancement of InGaN/GaN solar cells with nanostructures

    SciTech Connect (OSTI)

    Bai, J.; Yang, C. C.; Athanasiou, M.; Wang, T.

    2014-02-03

    We demonstrate InGaN/GaN multi-quantum-well solar cells with nanostructures operating at a wavelength of 520?nm. Nanostructures with a periodic nanorod or nanohole array are fabricated by means of modified nanosphere lithography. Under 1 sun air-mass 1.5 global spectrum illumination, a fill factor of 50 and an open circuit voltage of 1.9?V are achieved in spite of very high indium content in InGaN alloys usually causing degradation of crystal quality. Both the nanorod array and the nanohole array significantly improve the performance of solar cells, while a larger enhancement is observed for the nanohole array, where the conversion efficiency is enhanced by 51%.

  12. Graphene in ohmic contact for both n-GaN and p-GaN

    SciTech Connect (OSTI)

    Zhong, Haijian; Liu, Zhenghui; Shi, Lin; Xu, Gengzhao; Fan, Yingmin; Huang, Zengli [Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou 215123 (China); Wang, Jianfeng; Ren, Guoqiang; Xu, Ke, E-mail: kxu2006@sinano.ac.cn [Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou 215123 (China); Suzhou Nanowin Science and Technology Co., Ltd., Suzhou 215123 (China)

    2014-05-26

    The wrinkles of single layer graphene contacted with either n-GaN or p-GaN were found both forming ohmic contacts investigated by conductive atomic force microscopy. The local I–V results show that some of the graphene wrinkles act as high-conductive channels and exhibiting ohmic behaviors compared with the flat regions with Schottky characteristics. We have studied the effects of the graphene wrinkles using density-functional-theory calculations. It is found that the standing and folded wrinkles with zigzag or armchair directions have a tendency to decrease or increase the local work function, respectively, pushing the local Fermi level towards n- or p-type GaN and thus improving the transport properties. These results can benefit recent topical researches and applications for graphene as electrode material integrated in various semiconductor devices.

  13. Graphene Monolayer Rotation on Ni(111) Facilities Bilayer Graphene Growth

    SciTech Connect (OSTI)

    Batzill M.; Sutter P.; Dahal, A.; Addou, R.

    2012-06-11

    Synthesis of bilayer graphene by chemical vapor deposition is of importance for graphene-based field effect devices. Here, we demonstrate that bilayer graphene preferentially grows by carbon-segregation under graphene sheets that are rotated relative to a Ni(111) substrate. Rotated graphene monolayer films can be synthesized at growth temperatures above 650 C on a Ni(111) thin-film. The segregated second graphene layer is in registry with the Ni(111) substrate and this suppresses further C-segregation, effectively self-limiting graphene formation to two layers.

  14. Temperature dependency of the emission properties from positioned In(Ga)As/GaAs quantum dots

    SciTech Connect (OSTI)

    Braun, T.; Schneider, C.; Maier, S.; Forchel, A.; Höfling, S.; Kamp, M.; Igusa, R.; Iwamoto, S.; Arakawa, Y.

    2014-09-15

    In this letter we study the influence of temperature and excitation power on the emission linewidth from site-controlled InGaAs/GaAs quantum dots grown on nanoholes defined by electron beam lithography and wet chemical etching. We identify thermal electron activation as well as direct exciton loss as the dominant intensity quenching channels. Additionally, we carefully analyze the effects of optical and acoustic phonons as well as close-by defects on the emission linewidth by means of temperature and power dependent micro-photoluminescence on single quantum dots with large pitches.

  15. 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)

    2013-08-12

    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.

  16. Effects of Process Conditions on Properties of Electroplated Ni Thin Films for Microsystem Applications

    E-Print Network [OSTI]

    Fleck, Norman A.

    Effects of Process Conditions on Properties of Electroplated Ni Thin Films for Microsystem, Southampton SO17 1QJ, United Kingdom The properties of electroplated Ni thin films have been systematically, micromotors, and pneumatic actuators.3-11 Ni and NiFe are the electroplated metals most commonly used for MEMS

  17. TiNi shape memory alloy thin films for microactuator application

    E-Print Network [OSTI]

    Fu, Yongqing

    TiNi films were prepared by co-sputtering TiNi target and a separate Ti target. Crystalline structure and phase transformation behaviors of TiNi films were investigated. Results showed that TiNi films had fine grain size ...

  18. Perpendicular magnetic anisotropy in ion beam sputtered Co/Ni multilayers

    E-Print Network [OSTI]

    Rasin, Boris

    2009-01-01

    Co/Ni multilayers display perpendicular magnetic anisotropy and have applications in magnetic devices that could lead to a large increase in the density of magnetic storage. Co/Ni 10-(2 Å Co/ 8Å Ni) and 10-(2 Å Co/ 4 Å Ni) ...

  19. Application of cluster-plus-glue-atom model to barrierless Cu–Ni–Ti and Cu–Ni–Ta films

    SciTech Connect (OSTI)

    Li, Xiaona, E-mail: lixiaona@dlut.edu.cn; Ding, Jianxin; Wang, Miao; Dong, Chuang [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024 (China); Chu, Jinn P. [Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China)

    2014-11-01

    To improve the thermal stability of copper and avoid its diffusion into surrounding dielectrics or interfacial reactions with them, the authors applied the cluster-plus-glue-atom model to investigate barrierless Cu–Ni–M (M?=?Ti or Ta) seed layers. The dissolution of the third element (Ti or Ta) in the Cu lattice with the aid of Ni significantly improved the thermal stability of the Cu seed layer. The appropriate M/Ni (M?=?Ti or Ta) ratio was selected to obtain a low resistivity: the resistivity was as low as 2.5??? cm for the (Ti{sub 1.5/13.5}Ni{sub 12/13.5}){sub 0.3}Cu{sub 99.7} film and 2.8??? cm for the (Ta{sub 1.1/13.1}Ni{sub 12/13.1}){sub 0.4}Cu{sub 99.6} film after annealing at 500?°C for 1?h. After annealing at 500?°C for 40?h, the two films remained stable without forming a Cu{sub 3}Si compound. The authors confirmed that the range of applications of the cluster-plus-glue-atom model could be extended. Therefore, a third element M with negative enthalpies of mixing with both Cu and Ni could be selected, under the premise that the mixing enthalpy of M–Ni is more negative than that of M–Cu.

  20. GaN based nanorods for solid state lighting

    SciTech Connect (OSTI)

    Li Shunfeng; Waag, Andreas [Institute of Semiconductor Technology, Braunschweig University of Technology, 38106 Braunschweig (Germany)

    2012-04-01

    In recent years, GaN nanorods are emerging as a very promising novel route toward devices for nano-optoelectronics and nano-photonics. In particular, core-shell light emitting devices are thought to be a breakthrough development in solid state lighting, nanorod based LEDs have many potential advantages as compared to their 2 D thin film counterparts. In this paper, we review the recent developments of GaN nanorod growth, characterization, and related device applications based on GaN nanorods. The initial work on GaN nanorod growth focused on catalyst-assisted and catalyst-free statistical growth. The growth condition and growth mechanisms were extensively investigated and discussed. Doping of GaN nanorods, especially p-doping, was found to significantly influence the morphology of GaN nanorods. The large surface of 3 D GaN nanorods induces new optical and electrical properties, which normally can be neglected in layered structures. Recently, more controlled selective area growth of GaN nanorods was realized using patterned substrates both by metalorganic chemical vapor deposition (MOCVD) and by molecular beam epitaxy (MBE). Advanced structures, for example, photonic crystals and DBRs are meanwhile integrated in GaN nanorod structures. Based on the work of growth and characterization of GaN nanorods, GaN nanoLEDs were reported by several groups with different growth and processing methods. Core/shell nanoLED structures were also demonstrated, which could be potentially useful for future high efficient LED structures. In this paper, we will discuss recent developments in GaN nanorod technology, focusing on the potential advantages, but also discussing problems and open questions, which may impose obstacles during the future development of a GaN nanorod based LED technology.

  1. Ni(NiO)/single-walled carbon nanotubes composite: Synthesis of electro-deposition, gas sensing property for NO gas and density functional theory calculation

    SciTech Connect (OSTI)

    Li, Li; Zhang, Guo; Chen, Lei; Bi, Hong-Mei; Shi, Ke-Ying

    2013-02-15

    Graphical abstract: The Ni(NiO)/semiconducting single-walled carbon nanotubes composite collected from the cathode after electro-deposition shows a high sensitivity to low-concentration NO gas at room temperature (18 °C). Display Omitted Highlights: ? Ni(NiO) nanoparticles were deposited on semiconducting SWCNTs by electro-deposition. ? Ni(NiO)/semiconducting SWCNTs film shows a high sensitivity to NO gas at 18 °C. ?Theoretical calculation reveals electron transfer from SWCNTs to NO via Ni. -- Abstract: Single-walled carbon nanotubes which contains metallic SWCNTs (m-SWCNTs) and semiconducting SWCNTs (s-SWCNTs) have been obtained under electric arc discharge. Their separation can be effectively achieved by the electro-deposition method. The Ni(NiO)/s-SWCNTs composite was found on cathode where Ni was partially oxidized to NiO at ambient condition with Ni(NiO) nanoparticles deposited uniformly on the bundles of SWCNTs. These results were confirmed by Raman spectra, transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV–vis–NIR and TG characterizations. Furthermore, investigation of the gas sensing property of Ni(NiO)/s-SWCNTs composite film to NO gas at 18 °C demonstrated the sensitivity was approximately 5% at the concentration of 97 ppb. Moreover, density functional theory (DFT) calculations were performed to explore the sensing mechanism which suggested the adsorption of NO molecules onto the composite through N–Ni interaction as well as the proposition of electron transfer mechanisms from SWCNTs to NO via the Ni medium.

  2. $^{64}$Ni+$^{64}$Ni fusion reaction calculated with the density-constrained time-dependent Hartree-Fock formalism

    E-Print Network [OSTI]

    A. S. Umar; V. E. Oberacker

    2007-09-25

    We study fusion reactions of the $^{64}$Ni+$^{64}$Ni system using the density-constrained time-dependent Hartree-Fock (TDHF) formalism. In this formalism the fusion barriers are directly obtained from TDHF dynamics. In addition, we incorporate the entrance channel alignments of the slightly deformed (oblate) $^{64}$Ni nuclei due to dynamical Coulomb excitation. We show that alignment leads to a fusion barrier distribution and alters the naive picture for defining which energies are actually sub-barrier. We also show that core polarization effects could play a significant role in fusion cross section calculations.

  3. Electrodeposition of amorphous matrix Ni-W/Wp̳ composites

    E-Print Network [OSTI]

    Jenket, Donald R. (Donald Robert)

    2005-01-01

    An amorphous Ni-W alloy matrix was incorporated with W particulate through two types of electrodeposition. The plating bath for the electrodeposition contained nickel sulfate, sodium tungstate, sodium citrate, ammonium ...

  4. Double dumbbell shaped AgNi alloy by pulsed electrodeposition

    SciTech Connect (OSTI)

    Dhanapal, K.; Vasumathi, M.; Santhi, Kalavathy [Materials Science Centre, Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600 025 (India); Narayanan, V., E-mail: stephen-arum@hotmail.com; Stephen, A., E-mail: stephen-arum@hotmail.com [Department of Inorganic Chemistry, University of Madras, Guindy Campus, Chennai-600 025 (India)

    2014-01-28

    Silver-Nickel is the well-known thermally immiscible system that makes them quite complex for the formation of alloy. This kind of alloy can be attained from electrodeposition method. In the present work, AgNi alloy was synthesized by pulsed electrodeposition in a single bath two electrode system with the use of anodic alumina membrane. The prepared AgNi alloy and pure Ag were characterized with X-ray Diffraction (XRD) for structural confirmation, Scanning Electron Microscopy (SEM) for morphological, and magnetic properties by Vibrating Sample Magnetometer, respectively. The X-ray Diffraction study shows the formation of cubic structure for pure Ag. SEM analysis reveals the double dumbbell morphology for AgNi alloy and spherically agglomeration for pure silver. Hysteresis behaviour from VSM measurement indicates that the AgNi alloy have good ferro-magnetic properties.

  5. TiNi-based thin films for MEMS applications

    E-Print Network [OSTI]

    Fu, Yongqing

    In this paper, some critical issues and problems in the development of TiNi thin films were discussed, including preparation and characterization considerations, residual stress and adhesion, frequency improvement, fatigue ...

  6. Grain boundary relaxation strengthening of nanocrystalline Ni–W alloys

    E-Print Network [OSTI]

    Rupert, Timothy J.

    The hardening effect caused by the relaxation of nonequilibrium grain boundary structure has been explored in nanocrystalline Ni–W alloys. First, the kinetics of relaxation hardening are studied, showing that higher annealing ...

  7. GaInP/GaAs dual junction solar cells on Ge/Si epitaxial templates Melissa J. Archer,1,a

    E-Print Network [OSTI]

    Atwater, Harry

    GaInP/GaAs dual junction solar cells on Ge/Si epitaxial templates Melissa J. Archer,1,a Daniel C, crack-free GaInP/GaAs double junction solar cells were grown by metal organic chemical vapor deposition with the world record efficiency is a metamorphic triple junction GaInP/GaAs/Ge cell.6 Alternatively, wafer

  8. Enhanced hole transport in InGaN/GaN multiple quantum well light-emitting

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    -emitting diodes (LEDs) are considered the new generation lighting sources due to their advantages in power Society of America OCIS codes: 230.3670, 230.5590, 160.6000. Nitride-based high-power light devoted to the development of high-brightness GaN-based LEDs [3­5]. Lateral hole spreading is one

  9. High-Efficiency GaInP/GaAs Tandem Solar Cells

    SciTech Connect (OSTI)

    Bertness, K. A.; Friedman, D. J.; Kurtz, S. R.; Kibbler, A. E.; Cramer, C.; Olson, J. M.

    1996-09-01

    GaInP/GaAs tandem solar cells have achieved efficiencies between 25.7-30.2%, depending on illumination conditions. The efficiencies are the highest confirmed two-terminal values measured for any solar cell within each standard illumination category. The monolithic, series-connected design of the tandem cells allows them to be substituted for silicon or gallium arsenide cells in photovoltaic panel systems with minimal design changes. The advantages of using GaInP/GaAs tandem solar cells in space and terrestrial applications are discussed primarily in terms of the reduction in balance-of-system costs that accrues when using a higher efficiency cell. The new efficiency values represent a significant improvement over previous efficiencies for this materials system, and we identify grid design, back interface passivation, and top interface passivation as the three key factors leading to this improvement. In producing the high-efficiency cells, we have addressed nondestructive diagnostics and materials growth reproducibility as well as peak cell performance.

  10. High-efficiency GaInP/GaAs tandem solar cells

    SciTech Connect (OSTI)

    Bertness, K.A.; Friedman, D.J.; Kurtz, S.R.; Kibbler, A.E.; Kramer, C.; Olson, J.M.

    1994-12-01

    GaInP/GaAs tandem solar cells have achieved new record efficiencies, specifically 25.7% under air-mass 0 (AM0) illumination, 29.5% under AM 1.5 global (AM1.5G) illumination, and 30.2% at 140-180x concentration under AM 1.5 direct (AM1.5D) illumination. These values are the highest two-terminal efficiencies achieved by any solar cell under these illumination conditions. The monolithic, series-connected design of the tandem cells allows them to be substituted for silicon or gallium arsenide cells in photovoltaic panel systems with minimal design changes. The advantages of using GaInP/GaAs tandem solar cells in space and terrestrial applications are discussed primarily in terms of the reduction in balance-of-system costs that accrues when using a higher efficiency cell. The new efficiency values represent a significant improvement over previous efficiencies for this materials system, and we identify grid design, back interface passivation, and top interface passivation as the three key factors leading to this improvement. In producing the high-efficiency cells, we have addressed nondestructive diagnostics and materials growth reproducibility as well as peak cell performance. 31 refs.

  11. TJ Solar Cell (GaInP/GaAs/Ge Ultrahigh-Efficiency Solar Cells

    SciTech Connect (OSTI)

    Friedman, Daniel

    2002-04-17

    This talk will discuss recent developments in III-V multijunction photovoltaic technology which have led to the highest-efficiency solar cells ever demonstrated. The relationship between the materials science of III-V semiconductors and the achievement of record solar cell efficiencies will be emphasized. For instance, epitaxially-grown GAInP has been found to form a spontaneously-ordered GaP/InP (111) superlattice. This ordering affects the band gap of the material, which in turn affects the design of solar cells which incorporate GaInP. For the next generation of ultrahigh-efficiency III-V solar cells, we need a new semiconductor which is lattice-matched to GaAs, has a band gap of 1 eV, and has long minority-carrier diffusion lengths. Out of a number of candidate materials, the recently-discovered alloy GaInNAs appears to have the greatest promise. This material satisfies the first two criteria, but has to date shown very low diffusion lengths, a problem which is our current focus in the development of these next-generation cells.

  12. Multijunction GaInP/GaInAs/Ge solar cells with Bragg reflectors

    SciTech Connect (OSTI)

    Emelyanov, V. M. Kalyuzhniy, N. A.; Mintairov, S. A.; Shvarts, M. Z.; Lantratov, V. M.

    2010-12-15

    Effect of subcell parameters on the efficiency of GaInP/Ga(In)As/Ge tandem solar cells irradiated with 1-MeV electrons at fluences of up to 3 x 10{sup 15} cm{sup -2} has been theoretically studied. The optimal thicknesses of GaInP and GaInAs subcells, which provide the best photocurrent matching at various irradiation doses in solar cells with and without built-in Bragg reflectors, were determined. The dependences of the photoconverter efficiency on the fluence of 1-MeV electrons and on the time of residence in the geostationary orbit were calculated for structures optimized to the beginning and end of their service lives. It is shown that the optimization of the subcell heterostructures for a rated irradiation dose and the introduction of Bragg reflectors into the structure provide a 5% overall increase in efficiency for solar cells operating in the orbit compared with unoptimized cells having no Bragg reflector.

  13. Localized corrosion of GaAs surfaces and formation of porous GaAs

    SciTech Connect (OSTI)

    Schmuki, P.; Vitus, C.M.; Isaacs, H.S.; Fraser, J.; Graham, M.J.

    1995-12-01

    The present work deals with pitting corrosion of p- and n-type GaAs (100). Pit growth can be electrochemically initiated on both conduction types in chloride-containing solutions and leads after extended periods of time to the formation of a porous GaAs structure. In the case of p-type material, localized corrosion is only observed if a passivating film is present on the surface, otherwise -- e.g. in acidic solutions -- the material suffers from a uniform attack (electropolishing) which is independent of the anion present. In contrast, pitting corrosion of n-type material can be triggered independent of the presence of an oxide film. This is explained in terms of the different current limiting factor for the differently doped materials (oxide film in the case of the p- and a space charge layer in the case of the n-GaAs). The porous structure was characterized by SEM, EDX and AES, and consists mainly of GaAs. From scratch experiments it is clear that the pit initiation process is strongly influenced by surface defects. For n-type material, AFM investigations show that light induced roughening of the order of several hundred nm occurs under non-passivating conditions. This nm- scale roughening however does not affect the pitting process.

  14. Demonstration of a semipolar (10(1)over-bar(3)over-bar) InGaN/GaN green light emitting diode

    E-Print Network [OSTI]

    2005-01-01

    InGaN / GaN green light emitting diode R. Sharma, a? P. M.green ??525 nm? light emitting diode ?LED?. The fabricated

  15. Inverse spin Hall effect in Pt/(Ga,Mn)As

    SciTech Connect (OSTI)

    Nakayama, H.; Chen, L.; Chang, H. W.; Ohno, H.; Matsukura, F.

    2015-06-01

    We investigate dc voltages under ferromagnetic resonance in a Pt/(Ga,Mn)As bilayer structure. A part of the observed dc voltage is shown to originate from the inverse spin Hall effect. The sign of the inverse spin Hall voltage is the same as that in Py/Pt bilayer structure, even though the stacking order of ferromagnetic and nonmagnetic layers is opposite to each other. The spin mixing conductance at the Pt/(Ga,Mn)As interface is determined to be of the order of 10{sup 19?}m{sup ?2}, which is about ten times greater than that of (Ga,Mn)As/p-GaAs.

  16. Anomalous magnetic behavior in nanocomposite materials of reduced graphene oxide-Ni/NiFe{sub 2}O{sub 4}

    SciTech Connect (OSTI)

    Kollu, Pratap E-mail: anirmalagrace@vit.ac.in; Prathapani, Sateesh; Varaprasadarao, Eswara K.; Mallick, Sudhanshu; Bahadur, D. E-mail: anirmalagrace@vit.ac.in; Santosh, Chella; Grace, Andrews Nirmala E-mail: anirmalagrace@vit.ac.in

    2014-08-04

    Magnetic Reduced Graphene Oxide-Nickel/NiFe{sub 2}O{sub 4} (RGO-Ni/NF) nanocomposite has been synthesized by one pot solvothermal method. Respective phase formations and their purities in the composite are confirmed by High Resolution Transmission Electron Microscope and X Ray Diffraction, respectively. For the RGO-Ni/NF composite material finite-size effects lead to the anomalous magnetic behavior, which is corroborated in temperature and field dependent magnetization curves. Here, we are reporting the behavior of higher magnetization values for Zero Field Cooled condition to that of Field Cooled for the RGO-Ni/NF nanocomposite. Also, the observed negative and positive moments in Hysteresis loops at relatively smaller applied fields (100?Oe and 200?Oe) are explained on the basis of surface spin disorder.

  17. Shape memory behavior of ultrafine grained NiTi and TiNiPd shape memory alloys 

    E-Print Network [OSTI]

    Kockar, Benat

    2009-05-15

    The cyclic instability in shape memory characteristics of NiTi-based shape memory alloys (SMAs), such as transformation temperatures, transformation and irrecoverable strains and transformation hysteresis upon thermal and ...

  18. Deep level defects in n-type GaAsBi and GaAs grown at low temperatures

    SciTech Connect (OSTI)

    Mooney, P. M.; Watkins, K. P.; Jiang, Zenan; Basile, A. F.; Lewis, R. B.; Bahrami-Yekta, V.; Masnadi-Shirazi, M.; Beaton, D. A.; Tiedje, T.

    2013-04-07

    Deep level defects in n-type GaAs{sub 1-x}Bi{sub x} having 0 < x < 0.012 and GaAs grown by molecular beam epitaxy (MBE) at substrate temperatures between 300 and 400 Degree-Sign C have been investigated by Deep Level Capacitance Spectroscopy. Incorporating Bi suppresses the formation of an electron trap with activation energy 0.40 eV, thus reducing the total trap concentration in dilute GaAsBi layers by more than a factor of 20 compared to GaAs grown under the same conditions. We find that the dominant traps in dilute GaAsBi layers are defect complexes involving As{sub Ga}, as expected for MBE growth at these temperatures.

  19. High efficiency InGaN/GaN light emitting diodes with asymmetric triangular multiple quantum wells

    SciTech Connect (OSTI)

    Chang, Chiao-Yun; Li, Hen; Lu, Tien-Chang, E-mail: timtclu@mail.nctu.edu.tw [Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, 1001 University Road, Hsinchu, Taiwan 300 (China)

    2014-03-03

    In this study, we demonstrated high efficiency InGaN/GaN light emitting diodes (LEDs) with asymmetric triangular multiple quantum wells (MQWs). Asymmetric triangular MQWs not only contribute to uniform carrier distribution in InGaN/GaN MQWs but also yield a low Auger recombination rate. In addition, asymmetric triangular MQWs with gallium face-oriented inclination band profiles can be immune from the polarization charge originating from typical c-plane InGaN/GaN quantum well structures. In the experiment, LEDs incorporated with asymmetric triangular MQWs with gallium face-oriented inclination band profiles exhibited a 60.0% external quantum efficiency at 20?mA and a 27.0% efficiency droop at 100?mA (corresponding to a current density of 69?A/cm{sup 2}), which accounted for an 11.7% efficiency improvement and a 31.1% droop reduction compared with symmetric square quantum well structure LEDs.

  20. Deep level centers and their role in photoconductivity transients of InGaAs/GaAs quantum dot chains

    SciTech Connect (OSTI)

    Kondratenko, S. V. Vakulenko, O. V.; Mazur, Yu. I. Dorogan, V. G.; Marega, E.; Benamara, M.; Ware, M. E.; Salamo, G. J.

    2014-11-21

    The in-plane photoconductivity and photoluminescence are investigated in quantum dot-chain InGaAs/GaAs heterostructures. Different photoconductivity transients resulting from spectrally selecting photoexcitation of InGaAs QDs, GaAs spacers, or EL2 centers were observed. Persistent photoconductivity was observed at 80?K after excitation of electron-hole pairs due to interband transitions in both the InGaAs QDs and the GaAs matrix. Giant optically induced quenching of in-plane conductivity driven by recharging of EL2 centers is observed in the spectral range from 0.83?eV to 1.0?eV. Conductivity loss under photoexcitation is discussed in terms of carrier localization by analogy with carrier distribution in disordered media.

  1. Au impact on GaAs epitaxial growth on GaAs (111){sub B} substrates in molecular beam epitaxy

    SciTech Connect (OSTI)

    Liao, Zhi-Ming; Chen, Zhi-Gang; Xu, Hong-Yi; Guo, Ya-Nan; Sun, Wen; Zhang, Zhi; Yang, Lei; Lu, Zhen-Yu; Chen, Ping-Ping; Lu, Wei; Zou, Jin; Centre for Microscopy and Microanalysis, The University of Queensland, St. Lucia, Queensland 4072

    2013-02-11

    GaAs growth behaviour under the presence of Au nanoparticles on GaAs {l_brace}111{r_brace}{sub B} substrate is investigated using electron microscopy. It has been found that, during annealing, enhanced Ga surface diffusion towards Au nanoparticles leads to the GaAs epitaxial growth into {l_brace}113{r_brace}{sub B} faceted triangular pyramids under Au nanoparticles, governed by the thermodynamic growth, while during conventional GaAs growth, growth kinetics dominates, resulting in the flatted triangular pyramids at high temperature and the epitaxial nanowires growth at relatively low temperature. This study provides an insight of Au nanoparticle impact on GaAs growth, which is critical for understanding the formation mechanisms of semiconductor nanowires.

  2. Isotope correlations as a probe for freeze-out characterization: central 124Sn+64Ni, 112Sn+58Ni collisions

    E-Print Network [OSTI]

    E. Geraci; Reverse collaboration

    2003-10-15

    124Sn+64Ni and 112Sn+58Ni reactions at 35 AMeV incident energy were studied with the forward part of CHIMERA multi-detector. The most central collisions were selected by means of a multidimensional analysis. The characteristics of the source formed in the central collisions, as size, temperature and volume, were inspected. The measured isotopes of light fragments (3 <= Z <=8) were used to examine isotope yield ratios that provide information on the free neutron to proton densities.

  3. Electronic and structural influence of Ni by Pd substitution on the hydrogenation properties of TiNi

    SciTech Connect (OSTI)

    Emami, Hoda; Souques, Raphaeel; Crivello, Jean-Claude; Cuevas, Fermin

    2013-02-15

    In Ti (Ni,Pd) compounds, the hydrogen capacity and the stability of their hydrides decreases when Ni is partially substituted by larger in size Pd atoms. To understand this peculiar behaviour, the crystal structure of TiNi{sub 1-x}Pd{sub x}D{sub y} (x=0.1, 0.3 and 0.5) deuterides and the stability of TiNi{sub 1-x}Pd{sub x} (0{<=}x{<=}0.5) intermetallics and their hydrides have been investigated by both neutron diffraction experiments and Density Functional Theory (DFT) calculations. Neutron diffraction shows that at x=0.1 and 0.3, deuterium absorption induces tetragonal distortion in intermetallics sublattice whereas at x=0.5 the cubic symmetry is preserved. The structural properties and the heat of formation of TiNi{sub 1-x}Pd{sub x} (0{<=}x{<=}0.5) intermetallics and their hydrides have been determined by DFT. These results show that Pd substitution increases the stability of the intermetallics and decreases the stability of the hydrides, which confirms the rule of reverse stability. - Graphical abstract: Crystal structure of Ti(Ni,Pd)Hy hydrides in the I4/mmm space group. Highlights: Black-Right-Pointing-Pointer Neutron Diffraction and DFT calculations have been done on TiNi{sub 1-x}Pd{sub x}H{sub y} compounds. Black-Right-Pointing-Pointer Electronic effect of Pd substitution governs the hydrogenation properties in TiNi. Black-Right-Pointing-Pointer The rule of reverse stability in intermetallics/hydrides is observed with Pd substitution. Black-Right-Pointing-Pointer The hydrogen atoms in the I4/mmm structure prefer to occupy the 16n site.

  4. An inverted AlGaAs/GaAs patterned-Ge tunnel junction cascade concentrator solar cell

    SciTech Connect (OSTI)

    Venkatasubramanian, R. )

    1993-01-01

    This report describes work to develop inverted-grown Al[sub 0.34]Ga[sub 0.66]As/GaAs cascades. Several significant developments are reported on as follows: (1) The AM1.5 1-sun total-area efficiency of the top Al[sub 0.34]Ga[sub 0.66]As cell for the cascade was improved from 11.3% to 13.2% (NREL measurement [total-area]). (2) The cycled'' organometallic vapor phase epitaxy growth (OMVPE) was studied in detail utilizing a combination of characterization techniques including Hall-data, photoluminescence, and secondary ion mass spectroscopy. (3) A technique called eutectic-metal-bonding (EMB) was developed by strain-free mounting of thin GaAs-AlGaAs films (based on lattice-matched growth on Ge substrates and selective plasma etching of Ge substrates) onto Si carrier substrates. Minority-carrier lifetime in an EMB GaAs double-heterostructure was measured as high as 103 nsec, the highest lifetime report for a freestanding GaAs thin film. (4) A thin-film, inverted-grown GaAs cell with a 1-sun AM1.5 active-area efficiency of 20.3% was obtained. This cell was eutectic-metal-bonded onto Si. (5) A thin-film inverted-grown, Al[sub 0.34]Ga[sub 0.66]As/GaAs cascade with AM1.5 efficiency of 19.9% and 21% at 1-sun and 7-suns, respectively, was obtained. This represents an important milestone in the development of an AlGaAs/GaAs cascade by OMVPE utilizing a tunnel interconnect and demonstrates a proof-of-concept for the inverted-growth approach.

  5. DC characteristics of OMVPE-grown N-p-n InGaP/InGaAsN DHBTs

    SciTech Connect (OSTI)

    Li, N.Y.; Chang, P.C.; Baca, A.G.; Xie, X.M.; Sharps, P.R.; Hou, H.Q.

    2000-01-04

    The authors demonstrate, for the first time, a functional N-p-n heterojunction bipolar transistor using a novel material, InGaAsN, with a bandgap energy of 1.2eV as the p-type base layer. A 300{angstrom}-thick In{sub x}Ga{sub 1-x}As graded layer was introduced to reduce the conduction band offset at the p-type InGaAsN base and n-type GaAs collector junction. For an emitter size of 500 {mu}m{sup 2}, a peak current gain of 5.3 has been achieved.

  6. The Effect of the Thermal Boundary Resistance on Self-Heating of AlGaN/GaN HFETs

    E-Print Network [OSTI]

    sound velocity in GaN. The cut off wave vector is given by where NA is the Avogadro number, is the mass

  7. Reliability of AlGaN/GaN high electron mobility transistors on low dislocation density bulk GaN substrate: Implications of surface step edges

    SciTech Connect (OSTI)

    Killat, N., E-mail: Nicole.Killat@bristol.ac.uk, E-mail: Martin.Kuball@bristol.ac.uk; Montes Bajo, M.; Kuball, M., E-mail: Nicole.Killat@bristol.ac.uk, E-mail: Martin.Kuball@bristol.ac.uk [Center for Device Thermography and Reliability (CDTR), H.H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Paskova, T. [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States) [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States); Materials Science and Engineering Department, North Carolina State University, Raleigh, North Carolina 27695 (United States); Evans, K. R. [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States)] [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States); Leach, J. [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States) [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States); Electrical and Computer Engineering Department, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Li, X.; Özgür, Ü.; Morkoç, H. [Electrical and Computer Engineering Department, Virginia Commonwealth University, Richmond, Virginia 23284 (United States)] [Electrical and Computer Engineering Department, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Chabak, K. D.; Crespo, A.; Gillespie, J. K.; Fitch, R.; Kossler, M.; Walker, D. E.; Trejo, M.; Via, G. D.; Blevins, J. D. [Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433 (United States)] [Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433 (United States)

    2013-11-04

    To enable gaining insight into degradation mechanisms of AlGaN/GaN high electron mobility transistors, devices grown on a low-dislocation-density bulk-GaN substrate were studied. Gate leakage current and electroluminescence (EL) monitoring revealed a progressive appearance of EL spots during off-state stress which signify the generation of gate current leakage paths. Atomic force microscopy evidenced the formation of semiconductor surface pits at the failure location, which corresponds to the interaction region of the gate contact edge and the edges of surface steps.

  8. Istanbul,Turkey & Atlanta, GA Istanbul,Turkey

    E-Print Network [OSTI]

    Frantz, Kyle J.

    Istanbul,Turkey & Atlanta, GA Istanbul,Turkey & Atlanta, GA 2012 Media, Journalism and Business for departure to Istanbul,Turkey Day 9 Depart for Istanbul; guided cultural visit upon arrival; group dinner Day business leaders; site visits to local universities Day 18 UPS and the value of logistics inTurkey Day 19

  9. Photoeffects in WO{sub 3}/GaAs electrode

    SciTech Connect (OSTI)

    Yoon, K.H.; Lee, J.W.; Cho, Y.S.; Kang, D.H.

    1996-12-01

    Photoeffects of a {ital p}-type GaAs coated with WO{sub 3} thin film have been investigated as a function of film thickness and photoresponse transients of the WO{sub 3}/GaAs electrode were studied. Also, these results were compared to those for a single {ital p}-type GaAs electrode. The photocurrent of the WO{sub 3}/GaAs electrode depended on the film thickness of the WO{sub 3}, showing an optimum photon efficiency for specimens of 800 A thickness. This is due to the existence of an effective interface state within the band gap which reduces trapping of carriers and facilitates carrier movement. For an 800-A-thick WO{sub 3} thin film deposited {ital p}-GaAs photoelectrode, the photogenerated electrons were found to move to an electrolyte at a higher positive onset potential compared with that of single {ital p}-type GaAs, which was confirmed as a result of transient behavior. {ital I}{endash}{ital V} and {ital C}{endash}{ital V} characteristics of the WO{sub 3}/GaAs electrode were also compared with those of a single {ital p}-type GaAs electrode. {copyright} {ital 1996 American Institute of Physics.}

  10. Room temperature spin transport in undoped (110) GaAs/AlGaAs quantum wells

    SciTech Connect (OSTI)

    Yokota, Nobuhide Aoshima, Yohei; Ikeda, Kazuhiro; Kawaguchi, Hitoshi

    2014-02-17

    We are reporting on our first observation of a micrometer-order electron spin transport in a (110) GaAs/AlGaAs multiple quantum well (QW) at room temperature using a space- and time-resolved Kerr rotation technique. A 37-?m transport was observed within an electron spin lifetime of 1.2?ns at room temperature when using an in-plane electric field of 1.75?kV/cm. The spatio-temporal profiles of electron spins were well reproduced by the spin drift-diffusion equations coupled with the Poisson equation, supporting the validity of the measurement. The results suggest that (110) QWs are useful as a spin transport layer for semiconductor spintronic devices operating at room temperature.

  11. Evaluation of the two-photon absorption characteristics of GaSb/GaAs quantum rings

    SciTech Connect (OSTI)

    Wagener, M. C.; Botha, J. R.; Carrington, P. J.; Krier, A.

    2014-07-28

    The optical parameters describing the sub-bandgap response of GaSb/GaAs quantum rings solar cells have been obtained from photocurrent measurements using a modulated pseudo-monochromatic light source in combination with a second, continuous photo-filling source. By controlling the charge state of the quantum rings, the photoemission cross-sections describing the two-photon sub-bandgap transitions could be determined independently. Temperature dependent photo-response measurements also revealed that the barrier for thermal hole emission from the quantum rings is significantly below the quantum ring localisation energy. The temperature dependence of the sub-bandgap photo-response of the solar cell is also described in terms of the photo- and thermal-emission characteristics of the quantum rings.

  12. Sidewall passivation for InGaN/GaN nanopillar light emitting diodes

    SciTech Connect (OSTI)

    Choi, Won Hyuck; Abraham, Michael; Yu, Shih-Ying [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); You, Guanjun; Liu, Jie; Wang, Li; Xu, Jian, E-mail: jianxu@engr.psu.edu [Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Mohney, Suzanne E., E-mail: mohney@ems.psu.edu [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2014-07-07

    We studied the effect of sidewall passivation on InGaN/GaN multiquantum well-based nanopillar light emitting diode (LED) performance. In this research, the effects of varying etch rate, KOH treatment, and sulfur passivation were studied for reducing nanopillar sidewall damage and improving device efficiency. Nanopillars prepared under optimal etching conditions showed higher photoluminescence intensity compared with starting planar epilayers. Furthermore, nanopillar LEDs with and without sulfur passivation were compared through electrical and optical characterization. Suppressed leakage current under reverse bias and four times higher electroluminescence (EL) intensity were observed for passivated nanopillar LEDs compared with unpassivated nanopillar LEDs. The suppressed leakage current and EL intensity enhancement reflect the reduction of non-radiative recombination at the nanopillar sidewalls. In addition, the effect of sulfur passivation was found to be very stable, and further insight into its mechanism was gained through transmission electron microscopy.

  13. Large linear magnetoresistance in a GaAs/AlGaAs heterostructure

    SciTech Connect (OSTI)

    Aamir, Mohammed Ali, E-mail: aamir@physics.iisc.ernet.in; Goswami, Srijit, E-mail: aamir@physics.iisc.ernet.in; Ghosh, Arindam [Department of Physics, Indian Institute of Science, Bangalore 560 012 (India); Baenninger, Matthias; Farrer, Ian; Ritchie, David A. [Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Tripathi, Vikram [Department of Theoretical Physics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India); Pepper, Michael [Department of Electrical and Electronic Engineering, University College, London WC1E 7JE (United Kingdom)

    2013-12-04

    We report non-saturating linear magnetoresistance (MR) in a two-dimensional electron system (2DES) at a GaAs/AlGaAs heterointerface in the strongly insulating regime. We achieve this by driving the gate voltage below the pinch-off point of the device and operating it in the non-equilibrium regime with high source-drain bias. Remarkably, the magnitude of MR is as large as 500% per Tesla with respect to resistance at zero magnetic field, thus dwarfing most non-magnetic materials which exhibit this linearity. Its primary advantage over most other materials is that both linearity and the enormous magnitude are retained over a broad temperature range (0.3 K to 10 K), thus making it an attractive candidate for cryogenic sensor applications.

  14. Growth of GaN@InGaN Core-Shell and Au-GaN Hybrid Nanostructures for Energy Applications

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

    Kuykendall, Tevye; Aloni, Shaul; Jen-La Plante, Ilan; Mokari, Taleb

    2009-01-01

    We demonstrated a method to control the bandgap energy of GaN nanowires by forming GaN@InGaN core-shell hybrid structures using metal organic chemical vapor deposition (MOCVD). Furthermore, we show the growth of Au nanoparticles on the surface of GaN nanowires in solution at room temperature. The work shown here is a first step toward engineering properties that are crucial for the rational design and synthesis of a new class of photocatalytic materials. The hybrid structures were characterized by various techniques, including photoluminescence (PL), energy dispersive x-ray spectroscopy (EDS), transmission and scanning electron microscopy (TEM and SEM), and x-ray diffraction (XRD).

  15. Elastic properties of Pu metal and Pu-Ga alloys

    SciTech Connect (OSTI)

    Soderlind, P; Landa, A; Klepeis, J E; Suzuki, Y; Migliori, A

    2010-01-05

    We present elastic properties, theoretical and experimental, of Pu metal and Pu-Ga ({delta}) alloys together with ab initio equilibrium equation-of-state for these systems. For the theoretical treatment we employ density-functional theory in conjunction with spin-orbit coupling and orbital polarization for the metal and coherent-potential approximation for the alloys. Pu and Pu-Ga alloys are also investigated experimentally using resonant ultrasound spectroscopy. We show that orbital correlations become more important proceeding from {alpha} {yields} {beta} {yields} {gamma} plutonium, thus suggesting increasing f-electron correlation (localization). For the {delta}-Pu-Ga alloys we find a softening with larger Ga content, i.e., atomic volume, bulk modulus, and elastic constants, suggest a weakened chemical bonding with addition of Ga. Our measurements confirm qualitatively the theory but uncertainties remain when comparing the model with experiments.

  16. Transport properties of InGaAs/GaAs Heterostructures with {delta}-doped quantum wells

    SciTech Connect (OSTI)

    Baidus, N. V.; Vainberg, V. V.; Zvonkov, B. N.; Pylypchuk, A. S. Poroshin, V. N.; Sarbey, O. G.

    2012-05-15

    The lateral transport of electrons in single- and double-well pseudomorphic GaAs/n-InGaAs/GaAs heterostructures with quantum wells 50-100 meV deep and impurity {delta}-layers in the wells, with concentrations in the range 10{sup 11} < N{sub s} < 10{sup 12} cm{sup -2}, has been investigated. Single-well structures with a doped well at the center exhibit a nonmonotonic temperature dependence of the Hall coefficient and an increase in low-temperature electron mobility with an increase in the impurity concentration. The results obtained indicate that the impurity-band electron states play an important role in the conductivity of these structures. Involvement of the impurity band also allows to explain adequately the characteristics of the conductivity of double-well structures; in contrast to single-well structures, band bending caused by asymmetric doping is of great importance. The numerical calculations of conductivity within the model under consideration confirm these suggestions.

  17. Germanium subcells for multijunction GaInP/GaInAs/Ge solar cells

    SciTech Connect (OSTI)

    Kalyuzhnyy, N. A.; Gudovskikh, A. S.; Evstropov, V. V.; Lantratov, V. M.; Mintairov, S. A.; Timoshina, N. Kh.; Shvarts, M. Z.; Andreev, V. M.

    2010-11-15

    Photovoltaic converters based on n-GaInP/n-p-Ge heterostructures grown by the OMVPE under different conditions of formation of the p-n junction are studied. The heterostructures are intended for use as narrow-gap subcells of the GaInP/GaInAs/Ge three-junction solar cells. It is shown that, in Ge p-tn junctions, along with the diffusion mechanism, the tunneling mechanism of the current flow exists; therefore, the two-diode electrical equivalent circuit of the Ge p-n junction is used. The diode parameters are determined for both mechanisms from the analysis of both dark and 'light' current-voltage dependences. It is shown that the elimination of the component of the tunneling current allows one to increase the efficiency of the Ge subcell by {approx}1% with conversion of nonconcentrated solar radiation. The influence of the tunneling current on the efficiency of the Ge-based devices can be in practice reduced to zero at photogenerated current density of {approx}1.5 A/cm{sup 2} due to the use of the concentrated solar radiation.

  18. InGaN/GaN multiple-quantum-well light-emitting diodes with a grading InN composition suppressing the Auger recombination

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    ) In conventional InGaN/GaN light-emitting diodes (LEDs), thin InGaN quantum wells are usually adopted to mitigate recombination scales with the third power of the carrier density. As a result, the efficiency droop of the Auger recombination severely limits the LED performance. Here, we proposed and showed wide InGaN quantum wells

  19. Current crowding in GaInN / GaN LEDs grown on insulating substrates X. Guo, E. F. Schubert and J. Jahns

    E-Print Network [OSTI]

    Jahns, Jürgen

    Current crowding in GaInN / GaN LEDs grown on insulating substrates X. Guo, E. F. Schubert and J. Jahns Current crowding in mesa-structure GaInN/GaN light-emitting diodes (LEDs) grown on insulating and a saturation of the optical output power at high injection currents. It is shown that the optical power

  20. Investigation of the effect of temperature during off-state degradation of AlGaN/GaN High Electron Mobility Transistors

    E-Print Network [OSTI]

    Florida, University of

    , creating both electron traps and increasing electron tunneling through the defect states [4Investigation of the effect of temperature during off-state degradation of AlGaN/GaN High Electron 2011 a b s t r a c t AlGaN/GaN High Electron Mobility Transistors were found to exhibit a negative

  1. Mesoscopic photovoltaic effect in GaAs/Ga1-xAlxAs Aharonov-Bohm rings L. Angers, A. Chepelianskii, R. Deblock, B. Reulet, and H. Bouchiat

    E-Print Network [OSTI]

    Shepelyansky, Dima

    Mesoscopic photovoltaic effect in GaAs/Ga1-xAlxAs Aharonov-Bohm rings L. Angers, A. Chepelianskii specific dc voltage. We have investigated this photovoltaic PV effect on GaAs/Ga1-xAlxAs Aharonov is generally done by measuring the dc induced signal sometimes called photovoltaic effect which has also given

  2. Determination of two-dimensional electron and hole gas carriers in AlGaN/GaN/AlN heterostructures grown by Metal

    E-Print Network [OSTI]

    Ozbay, Ekmel

    between GaN and a sapphire substrate, the dislocation scattering mechanism and the electron spillover

  3. A combined capacitance-voltage and hard x-ray photoelectron spectroscopy characterisation of metal/Al{sub 2}O{sub 3}/In{sub 0.53}Ga{sub 0.47}As capacitor structures

    SciTech Connect (OSTI)

    Lin, Jun; Povey, Ian M.; Hurley, Paul K.; Walsh, Lee; Hughes, Greg; Woicik, Joseph C.; O'Regan, Terrance P.

    2014-07-14

    Capacitance-Voltage (C-V) characterization and hard x-ray photoelectron spectroscopy (HAXPES) measurements have been used to study metal/Al{sub 2}O{sub 3}/In{sub 0.53}Ga{sub 0.47}As capacitor structures with high (Ni) and low (Al) work function metals. The HAXPES measurements observe a band bending occurring prior to metal deposition, which is attributed to a combination of fixed oxide charges and interface states of donor-type. Following metal deposition, the Fermi level positions at the Al{sub 2}O{sub 3}/In{sub 0.53}Ga{sub 0.47}As interface move towards the expected direction as observed from HAXPES measurements. The In{sub 0.53}Ga{sub 0.47}As surface Fermi level positions determined from both the C-V analysis at zero gate bias and HAXPES measurements are in reasonable agreement. The results are consistent with the presence of electrically active interface states at the Al{sub 2}O{sub 3}/In{sub 0.53}Ga{sub 0.47}As interface and suggest an interface state density increasing towards the In{sub 0.53}Ga{sub 0.47}As valence band edge.

  4. Solving the stellar 62Ni problem with AMS

    E-Print Network [OSTI]

    I. Dillmann; T. Faestermann; G. Korschinek; J. Lachner; M. Maiti; M. Poutivtsev; G. Rugel; S. Walter; F. Käppeler; M. Erhard; A. R. Junghans; C. Nair; R. Schwengner; A. Wagner

    2009-07-01

    An accurate knowledge of the neutron capture cross sections of 62,63Ni is crucial since both isotopes take key positions which affect the whole reaction flow in the weak s process up to A=90. No experimental value for the 63Ni(n,gamma) cross section exists so far, and until recently the experimental values for 62Ni(n,gamma) at stellar temperatures (kT=30 keV) ranged between 12 and 37 mb. This latter discrepancy could now be solved by two activations with following AMS using the GAMS setup at the Munich tandem accelerator which are also in perfect agreement with a recent time-of-flight measurement. The resulting (preliminary) Maxwellian cross section at kT=30 keV was determined to be 30keV = 23.4 +/- 4.6 mb. Additionally, we have measured the 64Ni(gamma,n)63Ni cross section close to threshold. Photoactivations at 13.5 MeV, 11.4 MeV and 10.3 MeV were carried out with the ELBE accelerator at Forschungszentrum Dresden-Rossendorf. A first AMS measurement of the sample activated at 13.5 MeV revealed a cross section smaller by more than a factor of 2 compared to NON-SMOKER predictions.

  5. Modified Ni-Cu catalysts for ethanol steam reforming

    SciTech Connect (OSTI)

    Dan, M.; Mihet, M.; Almasan, V.; Borodi, G.; Katona, G.; Muresan, L.; Lazar, M. D.

    2013-11-13

    Three Ni-Cu catalysts, having different Cu content, supported on ?-alumina were synthesized by wet co-impregnation method, characterized and tested in the ethanol steam reforming (ESR) reaction. The catalysts were characterized for determination of: total surface area and porosity (N{sub 2} adsorption - desorption using BET and Dollimer Heal methods), Ni surface area (hydrogen chemisorption), crystallinity and Ni crystallites size (X-Ray Diffraction), type of catalytic active centers (Hydrogen Temperature Programmed Reduction). Total surface area and Ni crystallites size are not significantly influenced by the addition of Cu, while Ni surface area is drastically diminished by increasing of Cu concentration. Steam reforming experiments were performed at atmospheric pressure, temperature range 150-350°C, and ethanol - water molar ration of 1 at 30, using Ar as carrier gas. Ethanol conversion and hydrogen production increase by the addition of Cu. At 350°C there is a direct connection between hydrogen production and Cu concentration. Catalysts deactivation in 24h time on stream was studied by Transmission Electron Microscopy (TEM) and temperature-programmed reduction (TPR) on used catalysts. Coke deposition was observed at all studied temperatures; at 150°C amorphous carbon was evidenced, while at 350°C crystalline, filamentous carbon is formed.

  6. Superior performance of Ni-W-Ce mixed-metal oxide catalysts for ethanol steam reforming: Synergistic effects of W- and Ni-dopants

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

    Rodriguez, Jose A.; Liu, Zongyuan; Xu, Wenqian; Yao, Siyu; Johnson-Peck, Aaron C.; Zhao, Fuzhen; Michorczyk, Piotr; Kubacka, Anna; Stach, Eric A.; Fernandez-Garica, Marcos; et al

    2014-11-26

    The ethanol steam reforming (ESR) reaction was studied over a series of Ni-W-Ce oxide catalysts. The structures of the catalysts were characterized using in-situ techniques including X-ray diffraction, Pair Distribution Function, X-ray absorption fine structure and transmission electron microscopy; while possible surface intermediates for the ESR reaction were investigated by Diffuse Reflectance Infrared Fourier Transform Spectroscopy. In these materials, all the W and part of the Ni were incorporated into the CeO? lattice, with the remaining Ni forming highly dispersed nano NiO (more »The Ni-W-Ce systeme exhibited a much larger lattice strain than those seen for Ni-Ce and W-Ce. Synergistic effects between Ni and W inside ceria produced a substantial amount of defects and O vacancies that led to high catalytic activity, selectivity and stability (i.e. resistance to coke formation) during ethanol steam reforming.« less

  7. Atomistic description of the electronic structure of InxGa1xAs alloys and InAsGaAs superlattices

    E-Print Network [OSTI]

    Kent, Paul

    quantum-wells15,20 (InxGa1 xAs)n /InP on InP and (InxGa1 xAs)n /GaAs on GaAs, and v GaAs-embedded InAs quantum dots.21­23 We wish to provide a uniform the- oretical description of the electronic structure-period dependence of the band offsets and interband transitions of InAs/GaAs systems on InP and GaAs substrates. DOI

  8. Improved hole distribution in InGaN/GaN light-emitting diodes with graded thickness quantum barriers

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    is 48.3%. Moreover, the light output power was enhanced from 770 mW for the ETQB LEDs to 870 m; accepted 3 June 2013; published online 19 June 2013) InGaN/GaN light-emitting diodes (LEDs) with graded , which is much smaller than that of the conventional equal-thickness quantum barriers (ETQB) LED, which

  9. Low-frequency noise in GaNAlGaN heterostructure field-effect transistors at cryogenic temperatures

    E-Print Network [OSTI]

    Pala, Nezih

    that the 1/f noise in GaN/AlGaN HFETs might be caused by electron tunneling from the channel to the traps was practically independent of the frequency of analysis. The model linking this maximum to the electron tunneling Department of Electrical, Computer, and Systems Engineering and Center for Integrated Electronics

  10. Development of GaAs/Si and GaAs/Si monolithic structures for future space solar cells

    SciTech Connect (OSTI)

    Spitzer, M.B.; Vernon, S.M.; Wolfson, R.G.; Tobin, S.P.

    1984-01-01

    The results of heteroepitaxial growth of GaAs and GaAlAs directly on Si are presented, and applications to new cell structures are suggested. The novel feature is the elimination of a Ge lattice transition region. This feature not only reduces the cost of substrate preparation, but also makes possible the fabrication of high efficiency monolithic cascade structures. All films to be discussed were grown by organometallic chemical vapor deposition at atmospheric pressure. This process yielded reproducible, large-area films of GaAs, grown directly on Si, that are tightly adherent and smooth, and are characterized by a defect density of 5 x 10(6) power/sq cm. Preliminary studies indicate that GaAlAs can also be grown in this way. A number of promising applications are suggested. Certainly these substrates are ideal for low-weight GaAs space solar ells. For very high efficiency, the absence of Ge makes the technology attractive for GaAlAs/Si monolithic cascades, in which the Si substrates would first be provided with a suitable p/n junction. An evaluation of a three bandgap cascade consisting of appropriately designed GaAlAs/GaAs/Si layers is also presented.

  11. Wavelength-resolved low-frequency noise of GaInN/GaN green light emitting diodes

    E-Print Network [OSTI]

    Wetzel, Christian M.

    Wavelength-resolved low-frequency noise of GaInN/GaN green light emitting diodes S. L. Rumyantseva well light emitting diodes. The light intensity noise was measured as a function of wavelength within the light emitting diode spectral emission line. The spectral noise density is found to increase

  12. GaAs-based self-aligned laser incorporating InGaP opto-electronic confinement layer

    E-Print Network [OSTI]

    be well suited for exploitation of long wavelength quantum dot and dilute nitride technology, resulting in single lateral mode emission from an In0.17Ga0.83As double quantum well laser. Introduction: Lasers based on the GaAs materials system offer advan- tages over their InP counterparts, such as the use

  13. Improved performance of In,,Ga...As/GaAs quantum dot solar cells via light scattering by nanoparticles

    E-Print Network [OSTI]

    Yu, Edward T.

    of QDs in the context of our work is attractive for achieving long wavelength absorption in solar cells enhancement at all infrared wave- lengths in the device photocurrent spectrum. Epitaxial layer structuresImproved performance of In,,Ga...As/GaAs quantum dot solar cells via light scattering

  14. Output Harmonic Termination Techniques for AlGaN/GaN HEMT Power Amplifiers Using Active Integrated Antenna Approach

    E-Print Network [OSTI]

    Itoh, Tatsuo

    Output Harmonic Termination Techniques for AlGaN/GaN HEMT Power Amplifiers Using Active Integrated 1200, Los Angeles, CA 90045 Abstract -- In this paper, effects of output harmonic terminations on PAE termination, we observe a substantial increase in PAE and output power. Further, we demonstrate the high

  15. SnO2 functionalized AlGaN/GaN high electron mobility transistor for hydrogen sensing applications

    E-Print Network [OSTI]

    Florida, University of

    for spacecraft and other long-term sensing applications. However, hydrogen is a dangerous gas for storage for monitoring leakage of hydrogen storage equipment and fuel tanks for spacecraft and hydrogen fuel cellSnO2 functionalized AlGaN/GaN high electron mobility transistor for hydrogen sensing applications

  16. Mn-doped Ga(As,P) and (Al,Ga)As ferromagnetic semiconductors: Electronic structure calculations 

    E-Print Network [OSTI]

    Masek, J.; Kudrnovsky, J.; Maca, F.; Sinova, Jairo; MacDonald, A. H.; Campion, R. P.; Gallagher, B. L.; Jungwirth, T.

    2007-01-01

    A remarkable progress towards functional ferromagnetic semiconductor materials for spintronics has been achieved in p-type (Ga,Mn)As. Robust hole-mediated ferromagnetism has, however, been observed also in other III-V hosts such as antimonides, Ga...

  17. DESIGN, GROWTH, FABRICATION AND CHARACTERIZATION OF HIGH-BAND GAP InGaN/GaN SOLAR CELLS

    E-Print Network [OSTI]

    Honsberg, Christiana

    photovoltaic efficiency of 39% at 236 suns is achieved by a triple-junction GaInP- GaInAs-Ge tandem solar cell [1]. While the achievable efficiency of triple-junction tandem solar cells is restricted to about 40% [2], modeling results show that a tandem solar cell of five junctions or greater, or an equivalent

  18. Progress toward technology transition of GaInP{sub 2}/GaAs/Ge multijunction solar cells

    SciTech Connect (OSTI)

    Keener, D.N.; Marvin, D.C.; Brinker, D.J.; Curtis, H.B.; Price, P.M.

    1997-12-31

    The objective of the joint WL/PL/NASA Multijunction Solar Cell Manufacturing Technology (ManTech) Program is to scale up high efficiency GaInP{sub 2}/GaAs/Ge multijunction solar cells to production size, quantity, and yield while limiting the production cost/Watt ($/W) to 15% over GaAs cells. Progress made by the program contractors, Spectrolab and TECSTAR, include, respectively, best cell efficiencies of 25.76% and 24.7% and establishment of 24.2% and 23.8% lot average efficiency baseline designs. The paper also presents side-by-side testing results collected by Phillips Laboratory and NASA Lewis on Phase 1 deliverable cells, which shows compliance with program objectives. Cell performance, pre- and post-radiation, and temperature coefficient results on initial production GaInP{sub 2}/GaAs/Ge solar cells will be presented.

  19. Mitigation of Sulfur Poisoning of Ni/Zirconia SOFC Anodes by Antimony and Tin

    SciTech Connect (OSTI)

    Marina, Olga A.; Coyle, Christopher A.; Engelhard, Mark H.; Pederson, Larry R.

    2011-02-28

    Surface Ni/Sb and Ni/Sb alloys were found to efficiently minimize the negative effects of sulfur on the performance of Ni/zirconia anode-supported solid oxide fuel cells (SOFC). Prior to operating on fuel gas containing low concentrations of H2S, the nickel/zirconia anodes were briefly exposed to antimony or tin vapor, which only slightly affected the SOFC performance. During the subsequent exposures to 1 and 5 ppm H2S, increases in anodic polarization losses were minimal compared to those observed for the standard nickel/zirconia anodes. Post-test XPS analyses showed that Sb and Sn tended to segregate to the surface of Ni particles, and further confirmed a significant reduction of adsorbed sulfur on the Ni surface in Ni/Sn and Ni/Sb samples compared to the Ni. The effect may be the result of weaker sulfur adsorption on bimetallic surfaces, adsorption site competition between sulfur and Sb or Sn on Ni, or other factors. The use of dilute binary alloys of Ni-Sb or Ni-Sn in the place of Ni, or brief exposure to Sb or Sn vapor, may be effective means to counteract the effects of sulfur poisoning in SOFC anodes and Ni catalysts. Other advantages, including suppression of coking or tailoring the anode composition for the internal reforming, are also expected.

  20. Bimetallic Fe-Ni Oxygen Carriers for Chemical Looping Combustion

    SciTech Connect (OSTI)

    Bhavsar, Saurabh; Veser, Goetz

    2013-11-06

    The relative abundance, low cost, and low toxicity of iron make Fe-based oxygen carriers of great interest for chemical looping combustion (CLC), an emerging technology for clean and efficient combustion of fossil and renewable fuels. However, Fe also shows much lower reactivity than other metals (such as Ni and Cu). Here, we demonstrate strong improvement of Fe-based carriers by alloying the metal phase with Ni. Through a combination of carrier synthesis and characterization with thermogravimetric and fixed-bed reactor studies, we demonstrate that the addition of Ni results in a significant enhancement in activity as well as an increase in selectivity for total oxidation. Furthermore, comparing alumina and ceria as support materials highlights the fact that reducible supports can result in a strong increase in oxygen carrier utilization.

  1. Healing of graphene on single crystalline Ni(111) films

    SciTech Connect (OSTI)

    Zeller, Patrick; Wintterlin, Joost; Speck, Florian; Ostler, Markus; Weinl, Michael; Schreck, Matthias; Seyller, Thomas

    2014-11-10

    The annealing of graphene layers grown on 150?nm thick single crystal Ni(111) films was investigated in situ by low energy electron microscopy and photoemission electron microscopy. After growth, by means of chemical vapor deposition of ethylene, the graphene layers consist of several domains showing different orientations with respect to the underlying Ni surface and also of small bilayer areas. It is shown that, in a controlled process, the rotated domains can be transformed into lattice-aligned graphene, and the bilayer areas can be selectively dissolved, so that exclusively the aligned monolayer graphene is obtained. The ordering mechanism involves transport of C atoms across the surface and solution in the bulk.

  2. Synthesis, electrochemistry and First Principles Calculation studies of layered Li-Ni-Ti-O compounds

    E-Print Network [OSTI]

    Kang, Kisuk

    New layered cathode materials, Li?.?Ni?.??Ti?.??O?, were synthesized by means of ion-exchange from Na?.?Ni?.??Ti?.??O?. The degree of cation disordering in the material depends critically on the synthesis conditions. Longer ...

  3. Effect of Aging Heat Treatments on Ni52Ti48 Shape Memory Alloy 

    E-Print Network [OSTI]

    Akin, Erhan

    2011-10-21

    Ni-rich NiTi shape memory alloys (SMAs) are capable of attaining a wide range of transformation temperatures depending on the heat treatment conditions and superior thermo-mechanical cycling stability, which are desired for repeated solid...

  4. Mechanism(s) of Ni Sorption on Al-Hydroxy-Interlayered Vermiculite Using Time-Resolved EXAFS

    E-Print Network [OSTI]

    Sparks, Donald L.

    Mechanism(s) of Ni Sorption on Al-Hydroxy-Interlayered Vermiculite Using Time-Resolved EXAFS D. R sorbed and the mechanism of Ni sorption. #12;

  5. Ferromagnetism in undoped One-dimensional GaN Nanowires

    SciTech Connect (OSTI)

    Jeganathan, K. E-mail: jagan@physics.bdu.ac.in; Purushothaman, V.; Debnath, R.; Arumugam, S.

    2014-05-15

    We report an intrinsic ferromagnetism in vertical aligned GaN nanowires (NW) fabricated by molecular beam epitaxy without any external catalyst. The magnetization saturates at ?0.75 × emu/gm with the applied field of 3000 Oe for the NWs grown under the low-Gallium flux of 2.4 × 10{sup ?8} mbar. Despite a drop in saturation magnetization, narrow hysteresis loop remains intact regardless of Gallium flux. Magnetization in vertical standing GaN NWs is consistent with the spectral analysis of low-temperature photoluminescence pertaining to Ga-vacancies associated structural defects at the nanoscale.

  6. Characterization of Zns-GaP Naon-composites

    SciTech Connect (OSTI)

    Todd, V.

    1993-12-09

    It proved possible to produce consistent, high-quality nanocrystalline ZnS powders with grain sizes as small as 8 nm. These powders are nano-porous and are readily impregnated with GaP precursor, although inconsistently. Both crystal structure and small grain size of the ZnS can be maintained through the use of GaP. Heat treatment of the impregnated powders results in a ZnS-GaP composite structure where the grain sizes of the phases are on the order of 10--20 nm. Conventional powder processing should be able to produce optically dense ceramic compacts with improved mechanical properties and suitable IR transmission.

  7. Superior performance of Ni-W-Ce mixed-metal oxide catalysts for ethanol steam reforming: Synergistic effects of W- and Ni-dopants

    SciTech Connect (OSTI)

    Rodriguez, Jose A.; Liu, Zongyuan; Xu, Wenqian; Yao, Siyu; Johnson-Peck, Aaron C.; Zhao, Fuzhen; Michorczyk, Piotr; Kubacka, Anna; Stach, Eric A.; Fernandez-Garica, Marcos; Senanayake, Sanjaya D.

    2014-11-26

    The ethanol steam reforming (ESR) reaction was studied over a series of Ni-W-Ce oxide catalysts. The structures of the catalysts were characterized using in-situ techniques including X-ray diffraction, Pair Distribution Function, X-ray absorption fine structure and transmission electron microscopy; while possible surface intermediates for the ESR reaction were investigated by Diffuse Reflectance Infrared Fourier Transform Spectroscopy. In these materials, all the W and part of the Ni were incorporated into the CeO? lattice, with the remaining Ni forming highly dispersed nano NiO (< 2 nm) outside the Ni-W-Ce oxide structure. The nano NiO was reduced to Ni under ESR conditions. The Ni-W-Ce systeme exhibited a much larger lattice strain than those seen for Ni-Ce and W-Ce. Synergistic effects between Ni and W inside ceria produced a substantial amount of defects and O vacancies that led to high catalytic activity, selectivity and stability (i.e. resistance to coke formation) during ethanol steam reforming.

  8. Superior performance of Ni-W-Ce mixed-metal oxide catalysts for ethanol steam reforming: Synergistic effects of W- and Ni-dopants

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

    Rodriguez, Jose A. [Brookhaven National Lab. (BNL), Upton, NY (United States); State Univ. of New York Stony Brook, Stony Brook, NY (United States); Liu, Zongyuan [Brookhaven National Lab. (BNL), Upton, NY (United States); State Univ. of New York Stony Brook, Stony Brook, NY (United States); Xu, Wenqian [Brookhaven National Lab. (BNL), Upton, NY (United States); Yao, Siyu [Brookhaven National Lab. (BNL), Upton, NY (United States); Johnson-Peck, Aaron C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Zhao, Fuzhen [Brookhaven National Lab. (BNL), Upton, NY (United States); Michorczyk, Piotr [Inst. de Catalisis y Petroleoquimica, Madrid (Spain); Kubacka, Anna [Inst. de Catalisis y Petroleoquimica, Madrid (Spain); Stach, Eric A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Fernandez-Garica, Marcos [State Univ. of New York Stony Brook, Stony Brook, NY (United States); Senanayake, Sanjaya D. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-01-01

    The ethanol steam reforming (ESR) reaction was studied over a series of Ni-W-Ce oxide catalysts. The structures of the catalysts were characterized using in-situ techniques including X-ray diffraction, Pair Distribution Function, X-ray absorption fine structure and transmission electron microscopy; while possible surface intermediates for the ESR reaction were investigated by Diffuse Reflectance Infrared Fourier Transform Spectroscopy. In these materials, all the W and part of the Ni were incorporated into the CeO? lattice, with the remaining Ni forming highly dispersed nano NiO (< 2 nm) outside the Ni-W-Ce oxide structure. The nano NiO was reduced to Ni under ESR conditions. The Ni-W-Ce systeme exhibited a much larger lattice strain than those seen for Ni-Ce and W-Ce. Synergistic effects between Ni and W inside ceria produced a substantial amount of defects and O vacancies that led to high catalytic activity, selectivity and stability (i.e. resistance to coke formation) during ethanol steam reforming.

  9. XES Nanoprobe for Hard X-Ray Region: Mitigating Degradation in Ni-ZEBRA Batteries Research Team: Mark Bowden, Kyle Alvine, Nancy Hess, Guosheng Li, Tamas Varga

    E-Print Network [OSTI]

    XES Nanoprobe for Hard X-Ray Region: Mitigating Degradation in Ni-ZEBRA Batteries Research Team scientific understanding of link between Ni-NiCl2 ZEBRA battery cycle degradation and FeS additive Chemical battery performance by poisoning Ni surfaces ­ optimizing Ni/NiCl2 distributions and conductive pathways

  10. Indium distribution at the interfaces of (Ga,In)(N,As)/GaAs quantum wells

    SciTech Connect (OSTI)

    Luna, E.; Ishikawa, F.; Batista, P. D.; Trampert, A. [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, D-10117, Berlin (Germany)

    2008-04-07

    The indium distribution across (Ga,In)(N,As) quantum wells is determined by using transmission electron microscopy techniques. Inside the quantum well, the indium distribution is well described by Muraki's segregation model; however, it fails in reflecting the concentration at the interfaces. To describe them, we propose a sigmoidal law which defines the smooth variation of the indium concentration with the position and provides a systematic and quantitative characterization of the interfaces. The thermal stability of the interfaces and their interplay with segregation effects are discussed. A connection between the high thermal robustness of the interfaces and the inherent thermodynamic miscibility gap of the alloy is suggested.

  11. Institut Jozef Stefan Odsek za reaktorsko tehniko

    E-Print Network [OSTI]

    ?umer, Slobodan

    Iztok Tiselj "Jozef Stefan Institute", Reactor Engineering Division & Chair of Nuclear Engineering of 11 operating reactors (control rods inserted). - cooling systems remove the residual heat from system: p~70 bar, T~285 oC source: NRC Nuclear Regulatory Commission #12;BWR reactor vessel h=20m diam.=5

  12. Univerza v Ljubljani Fakulteta za elektrotehniko

    E-Print Network [OSTI]

    Ljubljana, University of

    Faculty of Electrical Engineering Bor Kos Numerical computation of electromagnetic fields in the human during the PhD study period at the Laboratory of Biocybernetics, Faculty of Electrical Engineering, Miklavcic D, Kos B, Zupanic A, Mali B, Jarm T, Pavliha D, Marcan M, Gasljevic G, Gorjup V, Music M, Vavpotic

  13. Oxygen Reduction Activity of PtxNi1-x Alloy Nanoparticles on Multiwall Carbon Nanotubes

    E-Print Network [OSTI]

    Kim, Junhyung

    PtxNi1 - x nanoparticles (Pt:Ni; 1:0, 4:1, 3:1 and 0.7:1) of ~5 nm, were synthesized on carboxylic acid-functionalized multiwall carbon nanotubes (PtxNi1 - x NPs/MWNT). The oxygen reduction reaction (ORR) activity measurements ...

  14. CO2 hydrogenation to formic acid on Ni(110) Guowen Peng a

    E-Print Network [OSTI]

    Sibener, Steven

    CO2 hydrogenation to formic acid on Ni(110) Guowen Peng a , S.J. Sibener b , George C. Schatz c of subsurface H for hydrogenating carbon dioxide (CO2) on Ni(110). The energetics of surface and subsurface H reacting with surface CO2 to form for- mate, carboxyl, and formic acid on Ni(110) is systematically studied

  15. Local Structures and Interface Morphology of InGaAsN Thin Films Grown on GaAs

    SciTech Connect (OSTI)

    Allerman, A.A.; Chen, J.G.; Geisz, J.F.; Huang, S.; Hulbert, S.L.; Jones, E.D.; Kao, Y.H.; Kurtz, S.; Kurtz, S.R.; Olson, J.M.; Soo, Y.L.

    1999-02-23

    The compound semiconductor system InGaAsN exhibits many intriguing properties which are particularly useful for the development of innovative high efficiency thin film solar cells and long wavelength lasers. The bandgap in these semiconductors can be varied by controlling the content of N and In and the thin films can yet be lattice-matched to GaAs. In the present work, x-ray absorption fine structure (XAFS) and grazing incidence x-ray scattering (GIXS) techniques have been employed to probe the local environment surrounding both N and In atoms as well as the interface morphology of InGaAsN thin films epitaxially grown on GaAs. The soft x-ray XAFS results around nitrogen K-edge reveal that N is in the sp{sup 3} hybridized bonding configuration in InGaAsN and GaAsN, suggesting that N impurities most likely substitute for As sites in these two compounds. The results of In K-edge XAFS suggest a possible trend of a slightly larger coordination number of As nearest neighbors around In atoms in InGaAsN samples with a narrower bandgap whereas the In-As interatomic distance remains practically the same as in InAs within the experimental uncertainties. These results combined suggest that N-substitution of the As sites plays an important role of bandgap-narrowing while in the meantime counteracting the compressive strain caused by In-doping. Grazing incidence x-ray scattering (GIXS) experiments verify that InGaAsN thin films can indeed form very smooth interfaces with GaAs yielding an average interfacial roughness of 5-20{angstrom}.

  16. Structural and optical properties of GaAs-based heterostructures with Ge and Ge/InGaAs quantum wells

    SciTech Connect (OSTI)

    Aleshkin, V. Ya.; Dubinov, A. A., E-mail: sanya@ipm.sci-nnov.ru; Drozdov, M. N. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Zvonkov, B. N. [Nizhni Novgorod State University, Research Physical Technical Institute (Russian Federation); Kudryavtsev, K. E.; Tonkikh, A. A.; Yablonskiy, A. N. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Werner, P. [Max Planck Institute of Microstructure Physics (Germany)

    2013-05-15

    GaAs-based heterostructures with Ge and Ge/InGaAs quantum wells are grown by laser-assisted sputtering. Structural and optical studies of the heterostructures are carried out. A broad photoluminescence line is observed in the wavelength range from 1300 to 1650 nm. The line corresponds to indirect transitions in the momentum space of the Ge quantum wells and to transitions between the In{sub 0.28}Ga{sub 0.72}As and Ge layers, indirect in coordinate space, but direct in momentum space.

  17. Electrical spin injection using GaCrN in a GaN based spin light emitting diode

    SciTech Connect (OSTI)

    Banerjee, D.; Ganguly, S.; Saha, D.; Adari, R.; Sankaranarayan, S.; Kumar, A.; Aldhaheri, R. W.; Hussain, M. A.; Balamesh, A. S.

    2013-12-09

    We have demonstrated electrical spin-injection from GaCrN dilute magnetic semiconductor (DMS) in a GaN-based spin light emitting diode (spin-LED). The remanent in-plane magnetization of the thin-film semiconducting ferromagnet has been used for introducing the spin polarized electrons into the non-magnetic InGaN quantum well. The output circular polarization obtained from the spin-LED closely follows the normalized in-plane magnetization curve of the DMS. A saturation circular polarization of ?2.5% is obtained at 200?K.

  18. Effects of light illumination on electron velocity of AlGaN/GaN heterostructures under high electric field

    SciTech Connect (OSTI)

    Guo, Lei; Yang, Xuelin Cheng, Jianpeng; Sang, Ling; Xu, Fujun; Tang, Ning; Feng, Zhihong; Lv, Yuanjie; Wang, Xinqiang; Shen, B.; Ge, Weikun

    2014-12-15

    We have investigated the variation of electron velocity in AlGaN/GaN heterostructures depending on illuminating light intensity and wavelength. It is shown that the electron velocity at high electric field increases under above-band light illumination. This electron velocity enhancement is found to be related to the photo-generated cold holes which interact with hot electrons and thus accelerate the energy relaxation at high electric field. The results suggest an alternative way to improve the electron energy relaxation rate and hence the electron velocity in GaN based heterostructures.

  19. High-power InGaAs/GaAs quantum-well laser with enhanced broad spectrum of stimulated emission

    SciTech Connect (OSTI)

    Wang, Huolei; Yu, Hongyan; Zhou, Xuliang; Kan, Qiang; Yuan, Lijun; Wang, Wei; Pan, Jiaoqing, E-mail: jqpan@semi.ac.cn [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Science, Beijing 100083 (China); Chen, Weixi [State Key Lab for Mesoscopic Physics and School of Physics, Peking University, Beijing 100871 (China); Ding, Ying, E-mail: Ying.Ding@glasgow.ac.uk [School of Engineering, University of Glasgow, Glasgow G12 8LT (United Kingdom)

    2014-10-06

    We report the demonstration of an InGaAs/GaAs quantum well (QW) broadband stimulated emission laser with a structure that integrated a GaAs tunnel junction with two QW active regions. The laser exhibits ultrabroad lasing spectral coverage of ?51?nm at a center wavelength of 1060?nm with a total emission power of 790 mW, corresponding to a high average spectral power density of 15.5 mW/nm, under pulsed current conditions. Compared to traditional lasers, this laser with an asymmetric separate-confinement heterostructure shows broader lasing bandwidth and higher spectral power density.

  20. Linear and nonlinear optical properties of GaAs/Al{sub x}Ga{sub 1?x}As/GaAs/Al{sub y}Ga{sub 1?y}As multi-shell spherical quantum dot

    SciTech Connect (OSTI)

    Emre Kavruk, Ahmet E-mail: aekavruk@gmail.com; Koc, Fatih; Sahin, Mehmet E-mail: mehsahin@gmail.com

    2013-11-14

    In this work, the optical properties of GaAs/Al{sub x}Ga{sub 1?x}As/GaAs/Al{sub y}Ga{sub 1?y}As multi-shell quantum dot heterostructure have been studied as a function of Al doping concentrations for cases with and without a hydrogenic donor atom. It has been observed that the absorption coefficient strength and/or resonant absorption wavelength can be adjusted by changing the Al content of inner-barrier and/or outer-barrier regions. Besides, it has been shown that the donor atom has an important effect on the control of the electronic and optical properties of the structure. The results have been presented as a function of the Al contents of the inner-barrier x and outer-barrier y regions and probable physical reasons have been discussed.

  1. Electrical degradation mechanisms of RF power GaAs PHEMTs

    E-Print Network [OSTI]

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

    2007-01-01

    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 ...

  2. Evaporation-based Ge/.sup.68 Ga Separation

    DOE Patents [OSTI]

    Mirzadeh, Saed (Albuquerque, NM); Whipple, Richard E. (Los Alamos, NM); Grant, Patrick M. (Los Alamos, NM); O'Brien, Jr., Harold A. (Los Alamos, NM)

    1981-01-01

    Micro concentrations of .sup.68 Ga in secular equilibrium with .sup.68 Ge in strong aqueous HCl solution may readily be separated in ionic form from the .sup.68 Ge for biomedical use by evaporating the solution to dryness and then leaching the .sup.68 Ga from the container walls with dilute aqueous solutions of HCl or NaCl. The chloro-germanide produced during the evaporation may be quantitatively recovered to be used again as a source of .sup.68 Ga. If the solution is distilled to remove any oxidizing agents which may be present as impurities, the separation factor may easily exceed 10.sup.5. The separation is easily completed and the .sup.68 Ga made available in ionic form in 30 minutes or less.

  3. Investigation of Ni Sorption on Pyrophyllite: An XAFS Study

    E-Print Network [OSTI]

    Sparks, Donald L.

    , * , G E R A L D I N E M . L A M B L E , A N D D O N A L D L . S P A R K S Department of Plant and SoilInvestigation of Ni Sorption on Pyrophyllite: An XAFS Study A N D R E M . S C H E I D E G G E R

  4. Semantic Sensor Net: An Extensible Framework Lionel M. Ni1

    E-Print Network [OSTI]

    Liu, Yunhao

    (MEMS) have led to the wide deployment of large-scale wireless sensor networks (WSN), which promisesSemantic Sensor Net: An Extensible Framework Lionel M. Ni1 , Yanmin Zhu1 , Jian Ma1 , Minglu Li2-ml@cs.sjtu.edu.cn Abstract. Existing approaches for sensor networks suffer from a number of critical drawbacks. First

  5. High strain rate deformation of NiAl

    SciTech Connect (OSTI)

    Maloy, S.A.; Gray, G.T. III; Darolia, R.

    1994-07-01

    NiAl is a potential high temperature structural material. Applications for which NiAl is being considered (such as rotating components in jet engines) requires knowledge of mechanical properties over a wide range of strain rates. Single crystal NiAl (stoichiometric and Ni 49.75Al 0.25Fe) has been deformed in compression along [100] at strain rates of 0.001, 0.1/s and 2000/s and temperatures of 76,298 and 773K. <111> slip was observed after 76K testing at a strain rate of 0.001/s and 298K testing at a strain rate of 2000/s. Kinking was observed after deformation at 298K and a strain rate of 0.001/s and sometimes at 298 K and a strain rate of 0.1/s. Strain hardening rates of 8200 and 4000 MPa were observed after 773 and 298K testing respectively, at a strain rate of 2000/s. Results are discussed in reference to resulting dislocation substructure.

  6. 90° magnetic coupling in a NiFe/FeMn/biased NiFe multilayer spin valve component investigated by polarized neutron reflectometry

    SciTech Connect (OSTI)

    Callori, S. J., E-mail: sara.callori@ansto.gov.au; Bertinshaw, J. [School of Physics, The University of New South Wales, Sydney, New South Wales 2052 (Australia); Bragg Institute, Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales 2234 (Australia); Cortie, D. L. [The Institute for Superconducting and Electronic Materials, The University of Wollongong, Wollongong, New South Wales 2522 (Australia); Bragg Institute, Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales 2234 (Australia); Cai, J. W., E-mail: jwcai@aphy.iphy.ac.cn; Zhu, T. [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Le Brun, A. P. [Bragg Institute, Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales 2234 (Australia); Klose, F. [Bragg Institute, Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales 2234 (Australia); Department of Physics and Materials Science, City University of Hong Kong (Hong Kong)

    2014-07-21

    We have observed 90° magnetic coupling in a NiFe/FeMn/biased NiFe multilayer system using polarized neutron reflectometry. Magnetometry results show magnetic switching for both the biased and free NiFe layers, the latter of which reverses at low applied fields. As these measurements are only capable of providing information about the total magnetization within a sample, polarized neutron reflectometry was used to investigate the reversal behavior of the NiFe layers individually. Both the non-spin-flip and spin-flip neutron reflectometry signals were tracked around the free NiFe layer hysteresis loop and were used to detail the evolution of the magnetization during reversal. At low magnetic fields near the free NiFe coercive field, a large spin-flip signal was observed, indicating magnetization aligned perpendicular to both the applied field and pinned layer.

  7. Low temperature carrier redistribution dynamics in InGaN/GaN quantum wells

    SciTech Connect (OSTI)

    Badcock, T. J., E-mail: Thomas.badcock@crl.toshiba.co.uk; Dawson, P.; Davies, M. J. [School of Physics and Astronomy, Photon Science Institute, Alan Turing Building, University of Manchester, Manchester M13 9PL (United Kingdom); Kappers, M. J.; Massabuau, F. C.-P.; Oehler, F.; Oliver, R. A.; Humphreys, C. J. [Department of Materials Science and Metallurgy, 27 Charles Babbage Road, University of Cambridge, Cambridge CB3 0FS (United Kingdom)

    2014-03-21

    We have studied the carrier recombination dynamics in an InGaN/GaN multiple quantum well structure as a function of emission energy and excitation density between temperatures of 10?K and 100?K. Under relatively low levels of excitation, the photoluminescence (PL) intensity and decay time of emission on the high energy side of the luminescence spectrum decrease strongly between 10?K and 50?K. In contrast, for emission detected on the low energy side of the spectrum, the PL intensity and decay time increase over the same temperature range. These results are consistent with a thermally activated carrier redistribution process in which the (temperature dependent) average timescale for carrier transfer into or out of a localised state depends on the energy of the given state. Thus, the transfer time out of shallow, weakly localised states is considerably shorter than the arrival time into more deeply localised states. This picture is consistent with carriers hopping between localisation sites in an uncorrelated disorder potential where the density of localised states decreases with increasing localisation depth, e.g., a exponential or Gaussian distribution resulting from random alloy disorder. Under significantly higher levels of excitation, the increased occupation fraction of the localised states results in a greater average separation distance between unoccupied localised states, causing a suppression of the spectral and dynamic signatures of the hopping transfer of carriers.

  8. 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)

    2014-11-03

    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.

  9. Influence of stress on optical transitions in GaN nanorods containing a single InGaN/GaN quantum disk

    SciTech Connect (OSTI)

    Zhuang, Y. D.; Shields, P. A.; Allsopp, D. W. E., E-mail: d.allsopp@bath.ac.uk [Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY (United Kingdom); Bruckbauer, J.; Edwards, P. R.; Martin, R. W. [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom)

    2014-11-07

    Cathodoluminescence (CL) hyperspectral imaging has been performed on GaN nanorods containing a single InGaN quantum disk (SQD) with controlled variations in excitation conditions. Two different nanorod diameters (200 and 280?nm) have been considered. Systematic changes in the CL spectra from the SQD were observed as the accelerating voltage of the electron beam and its position of incidence are varied. It is shown that the dominant optical transition in the SQD varies across the nanorod as a result of interplay between the contributions of the deformation potential and the quantum-confined Stark effect to the transition energy as consequence of radial variation in the pseudomorphic strain.

  10. High intensity low temperature (HILT) performance of space concentrator GaInP/GaInAs/Ge MJ SCs

    SciTech Connect (OSTI)

    Shvarts, Maxim Z., E-mail: shvarts@scell.ioffe.ru; Kalyuzhnyy, Nikolay A.; Mintairov, Sergey A.; Soluyanov, Andrei A.; Timoshina, Nailya Kh. [Ioffe Physical-Technical Institute, 26 Polytekhnicheskaya str., St.-Petersburg, 194021 (Russian Federation); Gudovskikh, Alexander S. [Saint-Petersburg Academic University - Nanotechnology Research and Education Centre RAS, St. Petersburg, 194021 (Russian Federation); Luque, Antonio [Ioffe Physical-Technical Institute, 26 Polytekhnicheskaya str., St.-Petersburg, 194021, Russia and Instituto de Energia Solar, Universidad Politecnica de Madrid, Madrid (Spain)

    2014-09-26

    In the work, the results of an investigation of GaInP/GaInAs/Ge MJ SCs intended for converting concentrated solar radiation, when operating at low temperatures (down to ?190 °C) are presented. A kink of the cell I-V characteristic has been observed in the region close to V{sub oc} starting from ?20°C at operation under concentrated sunlight. The causes for its occurrence have been analyzed and the reasons for formation of a built-in potential barrier for majority charge carriers at the n-GaInP/n-Ge isotype hetero-interface are discussed. The effect of charge carrier transport in n-GaInP/n-pGe heterostructures on MJ SC output characteristics at low temperatures has been studied including EL technique.

  11. The origin and reduction of switching noise in GaAs/AlGaAs lateral gated devices

    E-Print Network [OSTI]

    Davies, John H.

    to cryogenic temperature with all gates grounded to the substrate to protect against electrostatic effects in AlGaAs: electrons `freeze' into deep traps ­ DX centres ­ below about 150 K. The occupation of donors

  12. Design and fabrication of InGaN/GaN heterojunction bipolar transistors for microwave power amplifiers

    E-Print Network [OSTI]

    Keogh, David Martin

    2006-01-01

    assuming the material growth technology allows for all ofand a relatively immature growth technology, as well as theof the art for InGaN growth technology. Epitaxial growth of

  13. Polarization field engineering of GaN/AlN/AlGaN superlattices for enhanced thermoelectric properties

    SciTech Connect (OSTI)

    Sztein, Alexander, E-mail: asztein@umail.ucsb.edu [Materials Department, University of California, Santa Barbara, California 93106 (United States); Bowers, John E.; DenBaars, Steven P.; Nakamura, Shuji [Materials Department, University of California, Santa Barbara, California 93106 (United States); Electrical and Computer Engineering Department, University of California, Santa Barbara, California 93106 (United States)

    2014-01-27

    A novel polarization field engineering based strategy to simultaneously achieve high electrical conductivity and low thermal conductivity in thermoelectric materials is demonstrated. Polarization based electric fields are used to confine electrons into two-dimensional electron gases in GaN/AlN/Al{sub 0.2}Ga{sub 0.8}N superlattices, resulting in improved electron mobilities as high as 1176 cm{sup 2}/Vs and in-plane thermal conductivity as low as 8.9?W/mK. The resulting room temperature ZT values reach 0.08, a factor of four higher than InGaN and twelve higher than GaN, demonstrating the potential benefits of this polarization based engineering strategy for improving the ZT and efficiencies of thermoelectric materials.

  14. Si-CMOS-Like Integration of AlGaN/GaN Dielectric-Gated High-Electron-Mobility Transistors 

    E-Print Network [OSTI]

    Johnson, Derek Wade

    2014-07-31

    production is projected to consume ~100,000 wafers per year by 2015 (Yole Development, “Power GaN – 2012 Edition”), this manufacturing breakthrough represents potential savings of ~$17 million per year....

  15. Low-temperature magnetization in Ni-rich gamma-Ni100-x-yFexVy alloys 

    E-Print Network [OSTI]

    Chakraborty, S.; Mukherjee, GD; Rathnayaka, KDD; Naugle, Donald G.; Majumdar, AK.

    2000-01-01

    Detailed studies of the temperature dependence of the spontaneous magnetization have been made in eight different compositions of gamma-Ni100-x-yFexVy (4 less than or equal to x less than or equal to 17; 2 less than or equal to y less than or equal...

  16. Probing antiferromagnetism in NiMn/Ni/(Co)/Cu3Au(001) single-crystalline epitaxial thin films

    E-Print Network [OSTI]

    Kuch, Wolfgang

    hexagonal-close- packed and composition-modulated atomic layer stacking Appl. Phys. Lett. 102, 012407 (2013-of-plane (OoP) as well as in-plane (IP) magnetized Ni films, the latter stabilized by Co under-layer deposition) Electron molecular beam epitaxy: Layer-by-layer growth of complex oxides via pulsed electron

  17. First-principles investigations of Ni3Al(111) and NiAl(110) surfaces at metal dusting conditions

    SciTech Connect (OSTI)

    Saadi, Souheil

    2011-03-01

    We investigate the structure and surface composition of the {gamma}{prime}-Ni{sub 3}Al(111) and {beta}-NiAl(110) alloy surfaces at conditions relevant for metal dusting corrosion related to catalytic steam reforming of natural gas. In regular service as protective coatings, nickel-aluminum alloys are protected by an oxide scale, but in case of oxide scale spallation, the alloy surface may be directly exposed to the reactive gas environment and vulnerable to metal dusting. By means of density functional theory and thermochemical calculations for both the Ni{sub 3}Al and NiAl surfaces, the conditions under which CO and OH adsorption is to be expected and under which it is inhibited, are mapped out. Because CO and OH are regarded as precursors for nucleating graphite or oxide on the surfaces, phase diagrams for the surfaces provide a simple description of their stability. Specifically, this study shows how the CO and OH coverages depend on the steam to carbon ratio (S/C) in the gas and thereby provide a ranking of the carbon limits on the different surface phases.

  18. STRUCTURAL DETERMINATION OF MOLECULAR OVERLAYER SYSTEMS WITH NORMAL PHOTOELECTRON DIFFRACTION: c(2x2)CO-Ni(001) AND (/3 x /3)R30| Co-Ni(111)

    E-Print Network [OSTI]

    Kevan, S.D.

    2012-01-01

    electron diffraction (LEED), for subsequent, quantitativeadsorption system and because LEED structure analysis has° CO-Ni(lll) system, for which no LEED data presently exist.

  19. Optical investigation of InAs quantum dots inserted in AlGaAs/GaAs modulation doped heterostructure

    SciTech Connect (OSTI)

    Khmissi, H.; Baira, M.; Bouzaieene, L.; Saidi, F.; Maaref, H. [Laboratoire de Micro-optoelectronique et Nanostructures, Universite de Monastir (Tunisia); Sfaxi, L. [Laboratoire de Micro-optoelectronique et Nanostructures, Universite de Monastir (Tunisia); Universite de Sousse Faculte des Sciences de Monastir, Avenue de l'Environnement 5019 Monastir (Tunisia); Bru-Chevallier, C. [Institut des Nanotechnologies de Lyon (INL), CNRS UMR-5270, INSA-LYON, 7, Avenue Jean Capelle, Bat. Blaise Pascal, 69621 Villeurbanne (France)

    2011-03-01

    Optical properties of InAs quantum dots (QDs) inserted in AlGaAs/GaAs modulation doped heterostructure are investigated. To study the effect of carrier transfer behavior on the luminescence of self-assembled quantum dots, a series of sample has been prepared using molecular beam epitaxy (Riber 32 system) in which we have varied the thickness separating the delta dopage and the InAs quantum dots layer. Photoluminescence spectra show the existence of two peaks that can be attributed to transition energies from the ground state (E{sub 1}-HH{sub 1}) and the first excited state (E{sub 2}-HH{sub 2}). Two antagonist effects have been observed, a blue shift of the emission energies result from electron transferred from the AlGaAs/GaAs heterojunction to the InAs quantum dots and a red shift caused by the quantum confined Stark effect due to the internal electric field existing In the AlGaAs/GaAs heterojunction.

  20. Effects of high-temperature AIN buffer on the microstructure of AlGaN/GaN HEMTs

    SciTech Connect (OSTI)

    Coerekci, S.; Oeztuerk, M. K.; Yu, Hongbo; Cakmak, M.; Oezcelik, S.; Oezbay, E.

    2013-06-15

    Effects on AlGaN/GaN high-electron-mobility transistor structure of a high-temperature AlN buffer on sapphire substrate have been studied by high-resolution x-ray diffraction and atomic force microscopy techniques. The buffer improves the microstructural quality of GaN epilayer and reduces approximately one order of magnitude the edge-type threading dislocation density. As expected, the buffer also leads an atomically flat surface with a low root-mean-square of 0.25 nm and a step termination density in the range of 10{sup 8} cm{sup -2}. Due to the high-temperature buffer layer, no change on the strain character of the GaN and AlGaN epitaxial layers has been observed. Both epilayers exhibit compressive strain in parallel to the growth direction and tensile strain in perpendicular to the growth direction. However, an high-temperature AlN buffer layer on sapphire substrate in the HEMT structure reduces the tensile stress in the AlGaN layer.

  1. The thermal stability of TiB[sub 2] in Ni-43 a% Al

    SciTech Connect (OSTI)

    Korinko, P.S. (General Motors, Indianapolis, IN (United States). Allison Gas Turbine Div.); Duquette, D.J. (Rensselaer Polytechnic Inst., Troy, NY (United States))

    1994-02-01

    The intermetallic compound NiAl has been suggested for use as a matrix for high temperature composites. Interest in this compound is derived from its low density compared to conventional superalloys, high melting point, and excellent oxidation resistance. It has been demonstrated that a composite of stoichiometric NiAl and TiB[sub 2] is stable when exposed at elevated temperatures for extended periods of time. However, it has been shown that a composite consisting of Ni[sub 3]Al and TiB[sub 2] is not stable in the same temperature range. In the case of Ni[sub 3]Al, the TiB[sub 2] particles dissolve and the matrix is enriched with Ti and transforms to Ni[sub 3](Al,Ti) and NiTi. If stoichiometric NiAl reinforced with TiB[sub 2] is used in a high temperature oxidizing atmosphere, then there is also a possibility that the Al may be depleted as it is oxidized. If this occurs, the composition of the matrix may shift to nickel-rich NiAl or even to Ni[sub 3]Al. This work was conducted to determine if TiB[sub 2] is used in a high temperature oxidizing atmosphere, then there is also a possibility that the Al may be depleted as it is oxidized. If this occurs, the composition of the matrix may shift to nickel-rich NiAl or even to Ni[sub 3]Al. This work was conducted to determine if TiB[sub 2] is stable in nickel-rich NiAl. The Ni-Al phase diagram is shown, and the composition of NiAl used in this study is indicated.

  2. p-doping-free InGaN/GaN light-emitting diode driven by three-dimensional hole gas

    SciTech Connect (OSTI)

    Zhang, Zi-Hui; Tiam Tan, Swee; Kyaw, Zabu; Liu, Wei; Ji, Yun; Ju, Zhengang; Zhang, Xueliang [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore) [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); Wei Sun, Xiao, E-mail: EXWSUN@ntu.edu.sg [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); Department of Electronics and Electrical Engineering, South University of Science and Technology of China, Shenzhen, Guangdong 518055 (China); Volkan Demir, Hilmi, E-mail: VOLKAN@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); Department of Electrical and Electronics, UNAM-Institute of Material Science and Nanotechnology, Bilkent University, Ankara TR-06800 (Turkey); Department of Physics, UNAM-Institute of Material Science and Nanotechnology, Bilkent University, Ankara TR-06800 (Turkey)

    2013-12-23

    Here, GaN/Al{sub x}Ga{sub 1-x}N heterostructures with a graded AlN composition, completely lacking external p-doping, are designed and grown using metal-organic-chemical-vapour deposition (MOCVD) system to realize three-dimensional hole gas (3DHG). The existence of the 3DHG is confirmed by capacitance-voltage measurements. Based on this design, a p-doping-free InGaN/GaN light-emitting diode (LED) driven by the 3DHG is proposed and grown using MOCVD. The electroluminescence, which is attributed to the radiative recombination of injected electrons and holes in InGaN/GaN quantum wells, is observed from the fabricated p-doping-free devices. These results suggest that the 3DHG can be an alternative hole source for InGaN/GaN LEDs besides common Mg dopants.

  3. Lasing characteristics of GaSb/GaAs self-assembled quantum dots embedded in an InGaAs quantum well

    E-Print Network [OSTI]

    Jalali. Bahram

    Center for High Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, New Mexico, New Mexico 87545 Received 26 February 2007; accepted 1 June 2007; published online 28 June 2007 intriguing optoelectronic device possibilities on GaAs substrates including lasers, detectors, or solar cells

  4. Temperature-induced sign change of the magnetic interlayer coupling in Ni/Ni{sub 25}Mn{sub 75}/Ni trilayers on Cu{sub 3}Au(001)

    SciTech Connect (OSTI)

    Shokr, Y. A.; Zhang, B.; Sandig, O.; Kuch, W.; Erkovan, M.; Wu, C.-B.

    2015-05-07

    We investigated the magnetic interlayer coupling between two ferromagnetic (FM) Ni layers through an antiferromagnetic (AFM) Ni{sub 25}Mn{sub 75} layer and the influence of this coupling on the exchange bias phenomenon. The interlayer coupling energy of an epitaxial trilayer of 14 atomic monolayers (ML) Ni/45 ML Ni{sub 25}Mn{sub 75}/16 ML Ni on Cu{sub 3}Au(001) was extracted from minor-loop magnetization measurements using in-situ magneto-optical Kerr effect. The interlayer coupling changes from ferromagnetic to antiferromagnetic when the temperature is increased above 300?K. This sign change is interpreted as the result of the competition between an antiparallel Ruderman-Kittel-Kasuya-Yosida (RKKY)-type interlayer coupling, which dominates at high temperature, and a stronger direct exchange coupling across the AFM layer, which is present only below the Néel temperature of the AFM layer.

  5. Activity and structure of hydrotreating Ni, Mo, and Ni-Mo sulfide catalysts supported on {gamma}-Al{sub 2}O{sub 3}--USY zeolite

    SciTech Connect (OSTI)

    Li, D.; Nishijima, A.; Morris, D.E.; Guthrie, G.D.

    1999-11-15

    The catalytic hydrocracking (HC) of diphenylmethane (DPM) and hydrodesulfurization (HDS) of dibenzothiophene (DBT) over Ni, Mo, and Ni-Mo sulfide catalysts supported on a mixed ultrastable Y (USY) zeolite and gamma-Al{sub 2}O{sub 3} were studied. The catalysts were characterized using NH{sub 3} temperature-programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), UV-Vis-NIR diffuse reflectance spectroscopy (DRS), high-resolution transmission electron microscopy (HRTEM), and chemical composition analysis. Because addition of zeolite to a conventional alumina support improves acidity, Ni, Mo, and Ni-Mo catalysts supported on the combined supports had much higher HC activity. Ni was found to be uniformly distributed throughout the catalysts; however, Mo preferentially entered the structure of {gamma}-Al{sub 2}O{sub 3} or was accommodated as oxide aggregates on {gamma}-Al{sub 2}O{sub 3}, rather than associating with zeolite. Ni and Mo catalysts supported on {gamma}-Al{sub 2}O{sub 3}-USY zeolite were good HDS catalysts and showed a shallow maximum in catalytic activity at a NiO and MoO{sub 3} content of 5 mol%. The higher activity at this content occurred because Ni or Mo species had higher surface concentrations, higher dispersion, and were more easily sulfided. Ni-Mo catalysts supported on {gamma}-Al{sub 2}O{sub 3}-USY zeolite had high HDS activity, which showed a prominent maximum at a NiO/(NiO + MoO{sub 3}) ratio of about 0.4, because at this ratio the surface species of Ni and Mo were well dispersed and more easily sulfided to form a Ni-Mo-S phase responsible for the high HDS activity. The Ni-Mo catalysts supported on gamma-Al{sub 2}O{sub 3}-USY zeolite have slightly higher HDS activity than {gamma}-Al{sub 2}O{sub 3}-USY zeolite have slightly higher HDS activity than {gamma}-Al{sub 2}O{sub 3}-supported Ni-Mo catalysts.

  6. A 3-10 GHZLCR-matched Power Amplifier using Flip-Chip Mounted AlGaN/GaN HEMTs

    E-Print Network [OSTI]

    York, Robert A.

    amplifier using GaN- HEMTs-on-Sapphire. I INTRODUCTION GaN HEMTs have enormous potential for realizing high-power Traveling Wave Power Amplifier circuit (TWPA)[1][2] for realization of wideband power amplifiersWE4A-5 A 3-10 GHZLCR-matched Power Amplifier using Flip-Chip Mounted AlGaN/GaN HEMTs Jane J

  7. Intermixing of InGaAs/GaAs Quantum Well Using Multiple Cycles Annealing Cu-doped SiO2

    SciTech Connect (OSTI)

    Hongpinyo, V; Ding, Y H; Dimas, C E; Wang, Y; Ooi, B S; Qiu, W; Goddard, L L; Behymer, E M; Cole, G D; Bond, T C

    2008-06-11

    The authors investigate the effect of intermixing in InGaAs/GaAs quantum well structure using Cu-doped SiO{sub 2}. The incorporation of Cu into the silica film yields larger bandgap shift than typical impurity-free vacancy diffusion (IFVD) method at a lower activation temperature. We also observe enhancement of the photoluminescence (PL) signal from the intermixed InGaAs/GaAs quantum well structure after being cycle-annealed at 850 C.

  8. Metamorphic GaAsP buffers for growth of wide-bandgap InGaP solar cells J. Simon,1,a

    E-Print Network [OSTI]

    Haller, Gary L.

    . INTRODUCTION Triple-junction metamorphic solar cells have reached ef- ficiencies as high as 41.1% by combiningMetamorphic GaAsP buffers for growth of wide-bandgap InGaP solar cells J. Simon,1,a S. Tomasulo,1 P-yP solar cells. Tensile-strained GaAsxP1-x buffers grown on GaAs using unoptimized conditions

  9. FIRST DEMONSTRATION OF MONOLITHIC InP-BASED InAlAs/InGaAsP/InGaAs TRIPLE JUNCTION SOLAR CELLS

    E-Print Network [OSTI]

    Atwater, Harry

    FIRST DEMONSTRATION OF MONOLITHIC InP-BASED InAlAs/InGaAsP/InGaAs TRIPLE JUNCTION SOLAR CELLS RobynAlAs/InGaAsP/InGaAs triple junction solar cell grown on InP substrate. X-ray diffraction characterization shows high quality solar cell materials. Preliminary 1-sun AM1.5D testing of the triple junction solar cell shows promising

  10. Characterization of Cu(In,Ga)Se2 (CIGS) films with varying gallium ratios

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

    Claypoole, Jesse; Peace, Bernadette; Sun, Neville; Dwyer, Dan; Eisaman, Matthew D.; Haldar, Pradeep; Efstathiadis, Harry

    2015-09-05

    Cu(In1-x,Gax)Se2 (CIGS) absorber layers were deposited on molybdenum (Mo) coated soda-lime glass substrates with varying Ga content (described as Ga/(In+Ga) ratios) with respect to depth. As the responsible mechanisms for the limitation of the performance of the CIGS solar cells with high Ga contents are not well understood, the goal of this work was to investigate different properties of CIGS absorber films with Ga/(In+Ga) ratios varied between 0.29 and 0.41 (as determined by X-ray florescence spectroscopy (XRF)) in order to better understand the role that the Ga content has on film quality. The Ga grading in the CIGS layer hasmore »the effect causing a higher bandgap toward the surface and Mo contact while the band gap in the middle of the CIGS layer is lower. Also, a wider and larger Ga/(In+Ga) grading dip located deeper in the CIGS absorber layers tend to produce larger grains in the regions of the films that have lower Ga/(In+Ga) ratios. It was found that surface roughness decreases from 51.2 nm to 41.0 nm with increasing Ga/(In+Ga) ratios. However, the surface roughness generally decreases if the Ga grading occurs deeper in the absorber layer.« less

  11. Radiation damage of GaAs thin-film solar cells on Si substrates

    SciTech Connect (OSTI)

    Itoh, Y.; Yamaguchi, M.; Nishioka, T.; Yamamoto, A.

    1987-01-15

    1-MeV electron irradiation damages in GaAs thin-film solar cells on Si substrates are examined for the first time. Damage constant for minority-carrier diffusion length in GaAs heteroepitaxial films on Si substrates is found to be the same as that in GaAs homoepitaxial films on GaAs substrates. This agreement suggests that GaAs/Si has the same defect introduction rate with radiation as GaAs/GaAs. The degradation of GaAs solar cells on Si with electron irradiation is less than that of GaAs solar cells on GaAs, because in the present, GaAs films on Si substrates have lower minority-carrier diffusion length compared to GaAs films on GaAs and these films are insensitive to radiation. The p/sup +/-p/sup +/-n AlGaAs-GaAs heteroface solar cell with junction depth of about 0.3 ..mu..m is concluded to be useful for a high-efficiency and radiation-resistant solar cell fabricated on a Si substrate.

  12. Laser Gain and Threshold Properties in Compressive-Strained and Lattice-Matched GaInNAs/GaAs Quantum Wells

    SciTech Connect (OSTI)

    Chow, W.W.; Jones, E.D.; Modine, N.A.; Allerman, A.A.; Kurtz, S.R.

    1999-08-04

    The optical gain spectra for compressive-strained and lattice-matched GaInNAs/GaAs quantum wells are computed using a microscopic laser theory. From these spectra, the peak gain and carrier radiative decay rate as functions of carrier density are determined. These dependences allow the study of lasing threshold current density for different GAInNAs/GaAs laser structures.

  13. Contribution of alloy clustering to limiting the two-dimensional electron gas mobility in AlGaN/GaN and InAlN/GaN heterostructures: Theory and experiment

    SciTech Connect (OSTI)

    Ahmadi, Elaheh; Mishra, Umesh K. [Electrical and Computer Engineering Department, University of California, Santa Barbara, California 93106 (United States); Chalabi, Hamidreza [Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305 (United States); Kaun, Stephen W.; Shivaraman, Ravi; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2014-10-07

    The influence of alloy clustering on fluctuations in the ground state energy of the two-dimensional electron gas (2DEG) in AlGaN/GaN and InAlN/GaN heterostructures is studied. We show that because of these fluctuations, alloy clustering degrades the mobility even when the 2DEG wavefunction does not penetrate the alloy barrier unlike alloy disorder scattering. A comparison between the results obtained for AlGaN/GaN and InAlN/GaN heterostructures shows that alloy clustering limits the 2DEG mobility to a greater degree in InAlN/GaN heterostructures. Our study also reveals that the inclusion of an AlN interlayer increases the limiting mobility from alloy clustering. Moreover, Atom probe tomography is used to demonstrate the random nature of the fluctuations in the alloy composition.

  14. ''Bare'' single-particle energies in Ni-56 

    E-Print Network [OSTI]

    Trache, L.; Kolomiets, A.; Shlomo, S.; Heyde, K.; Dejbakhsh, H.; Gagliardi, Carl A.; Tribble, Robert E.; Zhou, XG; Jacob, VE; Oros, AM.

    1996-01-01

    of 57Ni and 57Cu that the lowest orbital in the N53 shell is 2p3/2 @1#. The first and second excited states in 57Ni at E*50.768 MeV, Jp55/22 and E*51.113 MeV, Jp51/22 have good single-particle character @2# and corre- spond to the next two orbitals.... A quick look higher into the energy spectrum shows a group of three levels of negative parity and spins Jp55/22, 7/22, and 3/22 around the energy of the first excited state in the core at E(211)52701 keV with half-lives T1/25 31, 47, and 12 fs...

  15. Auxiliary Ligand-Dependent Assembly of Several Ni/Ni-Cd Compounds with N2O2 Donor Tetradentate Symmetrical Schiff Base Ligand

    SciTech Connect (OSTI)

    Ge, Ying Ying; Li, Guo-Bi; Fang, Hua-Cai; Zhan, Xu Lin; Gu, Zhi-Gang; Chen, Jin Hao; Sun, Feng; Cai, Yue-Peng; Thallapally, Praveen K.

    2010-09-18

    Several low-dimensional Ni/Ni-Cd complexes containing N2O2 donor tetradentate symmetrical Schiff base ligand bis(acetylacetone)ethylene-diamine (sy-H2L2), namely, [Ni(sy-L2)]2?HLa?ClO4 (2), (HLa)2?(ClO4)?(NO3) (3), [Ni(sy-L2)X]2](4,4’-bipy) (where La = 5,7-dimethyl-3,6-dihydro-2H-1,4-diazepine, X = ClO4 (4), X=NO3 (5), [Ni(sy-L2)Cd(SCN)2]n (6) and [Ni(sy-L2)?Cd(N3)2]n (7) have been synthesized from [Ni(sy-L2)]2?H2O (1). Complex 2, is three component discrete assembly generated from (HLa)+ moiety bridged with [Ni(sy-L2)] unit and ClO4- anion. A solution containing complex 2 and Cd(NO3)2 results in a mixture of 1 and 3. Further re-crystallization of 1 and 3 with various auxiliary ligands, provides coordination complexes 4 – 7 stabilized by weak hydrogen bonds in which 6 and 7 represent the first 1D heteronuclear complexes based on symmetric acacen-base Schiff base ligand.

  16. Effects of thermo-mechanical treatment on the shape memory behavior of NiTi and CoNiAl alloys 

    E-Print Network [OSTI]

    Karaca, Haluk Ersin

    2004-09-30

    Nickel-Titanium (NiTi) shape memory alloys have been the focus of extensive research due to its unique characteristics such as high recoverable strain and ductility. However, solutionized samples of NiTi do not demonstrate good shape memory...

  17. Ni(OH){sub 2} nanoflakes electrodeposited on Ni foam-supported vertically oriented graphene nanosheets for application in asymmetric supercapacitors

    SciTech Connect (OSTI)

    Wang, Xin; Liu, Jiyue; Wang, Yayu; Zhao, Cuimei; Zheng, Weitao

    2014-04-01

    Highlights: • Ni(OH){sub 2}/vertically oriented graphene nanosheets (V-GNs) was prepared. • Ni(OH){sub 2}/V-GNs had enhanced specific capacitance, cycling reversibility and stability. • Performance of Ni(OH){sub 2}/GNs/NF-AC asymmetric supercapacitor was studied. - Abstract: Binderless Ni(OH){sub 2} nanoflakes grown on Ni foam (NF)-supported vertically oriented graphene nanosheets (V-GNs) has been fabricated as a positive electrode material for asymmetric supercapacitor (ASC), coupled with activated carbon (AC) as a counter electrode material. The introduction of V-GNs leads to dense growth of nanocrystalline ?-Ni(OH){sub 2} that is confirmed by X-ray diffraction, transmission electron microscopic and scanning electron microscopic analyses. The electrochemical performances of the Ni(OH){sub 2}/GNs/NF electrode are characterized by cyclic voltammetry and charge–discharge tests, which exhibit high specific capacitance of 2215 F g{sup ?1} at a scan current density of 2.3 A g{sup ?1}, enhanced cycling stability and high rate capability. The Ni(OH){sub 2}/GNs/NF-AC-based ASC can achieve a cell voltage of 1.4 V and a specific energy density of 11.11 Wh kg{sup ?1} at 0.5 mA cm{sup ?2} with a nearly 100% coulombic efficiency at room temperature.

  18. Sources of stress gradients in electrodeposited Ni MEMS.

    SciTech Connect (OSTI)

    Hearne, Sean Joseph; Floro, Jerrold Anthony; Dyck, Christopher William

    2004-06-01

    The ability of future integrated metal-semiconductor micro-systems such as RF MEMS to perform highly complex functions will depend on developing freestanding metal structures that offer improved conductivity and reflectivity over polysilicon structures. For example, metal-based RF MEMS technology could replace the bulky RF system presently used in communications, navigation, and avionics systems. However, stress gradients that induce warpage of active components have prevented the implementation of this technology. Figure 1, is an interference micrograph image of a series of cantilever beams fabricated from electrodeposited Ni. The curvature in the beams was the result of stress gradients intrinsic to the electrodeposition process. To study the sources of the stress in electrodeposition of Ni we have incorporated a wafer curvature based stress sensor, the multibeam optical stress sensor, into an electrodeposition cell. We have determined that there are two regions of stress induced by electrodepositing Ni from a sulfamate-based bath (Fig 2). The stress evolution during the first region, 0-1000{angstrom}, was determined to be dependent only on the substrate material (Au vs. Cu), whereas the stress evolution during the second region, >1000{angstrom}, was highly dependent on the deposition conditions. In this region, the stress varied from +0.5 GPa to -0.5GPa, depending solely on the deposition rate. We examined four likely sources for the compressive intrinsic stress, i.e. reduction in tensile stress, and determined that only the adatom diffusion into grain boundaries model of Sheldon, et al. could account for the observed compressive stress. In the presentation, we shall discuss the compressive stress generation mechanisms considered and the ramifications of these results on fabrication of electrodeposited Ni for MEMS applications.

  19. Precipitation in 18 wt% Ni maraging steel of grade 350

    SciTech Connect (OSTI)

    Tewari, R.; Mazumder, S.; Batra, I.S.; Dey, G.K.; Banerjee, S.

    2000-03-14

    The evolution of precipitates in maraging steel of grade 350 was studied using the complementary techniques of small angle X-ray scattering (SACS) and transmission electron microscopy (TEM). These investigations revealed that ageing the steel at 703 K involved a rhombohedral distortion of the supersaturated b.c.c. martensite accompanied by the appearance of diffuse {omega}-like structures. This was followed by the appearance of well-defined {omega} particles containing chemical order. At the ageing temperature of 783 K, Ni{sub 3}(Ti,Mo) precipitates were the first to appear with a growth exponent of 1/3. The values of the Pored exponent obtained from the SAXS profiles indicated that the {omega} particles, formed below 723 K, had diffuse interfaces up to an ageing time of 48 h. On the other hand, Ni{sub 3}(Ti,Mo) precipitates, formed above 723 K, developed sharp interfaces in just about an hour. Also, the steel exhibited scaling in phase separation both at 703 and 783 K, but only during the early stages. Through this study it was established that at temperatures of ageing less than 723 K, evolution of {omega} particles takes place through the collapse of the unstable b.c.c. lattice and, at temperatures above 723 K, precipitation of A{sub 3}B type of phases through the mechanism of clustering and ordering of atomic species. Sharp interfaces develop rather quickly when the mechanism of precipitation involves development and amplification of a concentration wave along as in the nucleation of Ni{sub 3}(Ti,Mo) at 783 K than when an interplay of both the displacement and concentration waves is required as in the evolution of {omega} at 703 K. These results indicate towards the possibility of existence of two separate time-temperature-transformation (TTT) curves, one for the evolution of {omega}-phase and another for nucleation and growth of Ni{sub 3}(Ti,Mo).

  20. Facile approach to prepare hollow core–shell NiO microspherers for supercapacitor electrodes

    SciTech Connect (OSTI)

    Han, Dandan; Xu, Pengcheng; Jing, Xiaoyan; Wang, Jun; Song, Dalei; Liu, Jingyuan; Zhang, Milin

    2013-07-15

    A facile lamellar template method (see image) has been developed for the preparation of uniform hollow core–shell structure NiO (HCS–NiO) with a nanoarchitectured wall structure. The prepared NiO was found to be highly crystalline in uniform microstructures with high specific surface area and pore volume. The results indicated that ethanol interacted with trisodium citrate played an important role for the formation of hollow core–shell spheres. On the basis of the analysis of the composition and the morphology, a possible formation mechanism was investigated. NiO microspheres with hollow core–shell showed excellent capacitive properties. The exceptional cyclic, structural and electrochemical stability with ?95% coulombic efficiency, and very low ESR value from impedance measurements promised good utility value of hollow core–shell NiO material in fabricating a wide range of high-performance electrochemical supercapacitors. - The hollow core–shell NiO was prepared with a facile lamellar template method. The prepared NiO show higher capacitance, lower ion diffusion resistance and better electroactive surface utilization for Faradaic reactions. - Highlights: • Formation of hollow core–shell NiO via a novel and facile precipitation route. • Exhibited uniform feature sizes and high surface area of hollow core–shell NiO. • Synthesized NiO has high specific capacitance ( 448 F g{sup 1}) and very low ESR value. • Increased 20% of long life cycles capability after 500 charge–discharge cycles.

  1. Present status of the KADoNiS database

    E-Print Network [OSTI]

    I. Dillmann; R. Plag; M. Heil; F. Käppeler; T. Rauscher

    2008-06-12

    The "Karlsruhe Astrophysical Database of Nucleosynthesis in Stars" (KADoNiS) project is an online database for experimental cross sections relevant to the $s$ process and $p$ process. It is available under \\http://nuclear-astrophysics.fzk.de/kadonis and consists of two parts. Part 1 is an updated sequel to the well-known Bao et al. compilations from 1987 and 2000, which is online since April 2005. An extension of this $s$-process database to $(n,p)$ and $(n,\\alpha)$ cross sections at $kT$= 30 keV, as in the first version of the Bao compilation, is planned. The second part of KADoNiS is a $p$-process library, which includes all available experimental data from $(p,\\gamma)$, $(p,n)$, $(\\alpha,\\gamma)$, $(\\alpha,n)$, $(\\alpha,\\alpha)$, $(n,\\alpha)$ and $(\\gamma,n)$ reactions in or close to the respective Gamow window. Despite the great number of reactions required for a $p$-process reaction network, experimental data is still scarce and up to now restricted to stable targets. Given here is a short overview about the present status of the KADoNiS database.

  2. Low temperature spin dynamics in Cr{sub 7}Ni-Cu-Cr{sub 7}Ni coupled molecular rings

    SciTech Connect (OSTI)

    Bordonali, L.; Furukawa, Y.; Mariani, M.; Sabareesh, K. P. V.; Garlatti, E.; Borsa, F.

    2014-05-07

    Proton Nuclear Magnetic Resonance (NMR) relaxation measurements have been performed down to very low temperature (50?mK) to determine the effect of coupling two Cr{sub 7}Ni molecular rings via a Cu{sup 2+} ion. No difference in the spin dynamics was found from nuclear spin lattice relaxation down to 1.5?K. At lower temperature, the {sup 1}H-NMR line broadens dramatically indicating spin freezing. From the plot of the line width vs. magnetization, it is found that the freezing temperature is higher (260?mK) in the coupled ring with respect to the single Cr{sub 7}Ni ring (140?mK)

  3. Nano-scale luminescence characterization of individual InGaN/GaN quantum wells stacked in a microcavity using scanning transmission electron microscope cathodoluminescence

    SciTech Connect (OSTI)

    Schmidt, Gordon Müller, Marcus; Veit, Peter; Bertram, Frank; Christen, Jürgen; Glauser, Marlene; Carlin, Jean-François; Cosendey, Gatien; Butté, Raphaël; Grandjean, Nicolas

    2014-07-21

    Using cathodoluminescence spectroscopy directly performed in a scanning transmission electron microscope at liquid helium temperatures, the optical and structural properties of a 62 InGaN/GaN multiple quantum well embedded in an AlInN/GaN based microcavity are investigated at the nanometer scale. We are able to spatially resolve a spectral redshift between the individual quantum wells towards the surface. Cathodoluminescence spectral linescans allow directly visualizing the critical layer thickness in the quantum well stack resulting in the onset of plastic relaxation of the strained InGaN/GaN system.

  4. Active region based on graded-gap InGaN/GaN superlattices for high-power 440- to 470-nm light-emitting diodes

    SciTech Connect (OSTI)

    Tsatsulnikov, A. F., E-mail: Andrew@beam.ioffe.ru; Lundin, W. V.; Sakharov, A. V.; Zavarin, E. E.; Usov, S. O.; Nikolaev, A. E.; Cherkashin, N. A.; Ber, B. Ya.; Kazantsev, D. Yu. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Mizerov, M. N. [Russian Academy of Sciences, Center for Microelectronics, Ioffe Physicotechnical Institute (Russian Federation); Park, Hee Seok [Samsung Electro-Mechanics Co. Ltd. (Korea, Republic of); Hytch, M.; Hue, F. [National Center for Scientific Research, Center for Material Elaboration and Structural Studies (France)

    2010-01-15

    The structural and optical properties of light-emitting diode structures with an active region based on ultrathin InGaN quantum wells limited by short-period InGaN/GaN superlattices from both sides have been investigated. The dependences of the external quantum efficiency on the active region design are analyzed. It is shown that the use of InGaN/GaN structures as limiting graded-gap short-period superlattices may significantly increase the quantum efficiency.

  5. Graphene/GaN diodes for ultraviolet and visible photodetectors

    SciTech Connect (OSTI)

    Lin, Fang; Chen, Shao-Wen; Meng, Jie; Tse, Geoffrey; Fu, Xue-Wen; Xu, Fu-Jun [State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871 (China); Shen, Bo; Liao, Zhi-Min, E-mail: liaozm@pku.edu.cn, E-mail: yudp@pku.edu.cn; Yu, Da-Peng, E-mail: liaozm@pku.edu.cn, E-mail: yudp@pku.edu.cn [State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China)

    2014-08-18

    The Schottky diodes based on graphene/GaN interface are fabricated and demonstrated for the dual-wavelength photodetection of ultraviolet (UV) and green lights. The physical mechanisms of the photoelectric response of the diodes with different light wavelengths are different. For UV illumination, the photo-generated carriers lower the Schottky barrier and increase the photocurrent. For green light illumination, as the photon energy is smaller than the bandgap of GaN, the hot electrons excited in graphene via internal photoemission are responsible for the photoelectric response. Using graphene as a transparent electrode, the diodes show a ?mS photoresponse, providing an alternative route toward multi-wavelength photodetectors.

  6. Polycrystalline MBE-grown GaAs for solar cells

    SciTech Connect (OSTI)

    Friedman, D.J.; Kurtz, S.R.; Kibbler, A.E.; Al-Jassim, M.; Jones, K.; Keyes, B.; Matson, R.

    1997-02-01

    This paper will discuss initial studies of thin-film GaAs grown by molecular-beam epitaxy for use in developing a thin-film GaAs solar cell. Photocurrent and photoluminescence intensity are related to the material morphology as a function of growth conditions. Growth temperature and V/III ratio have a dramatic effect on the photocurrent. However, it seems likely that even after optimizing such growth parameters, it will be necessary to provide substrates that can provide templates to enhance grain size from the start of thin-film growth. {copyright} {ital 1997 American Institute of Physics.}

  7. Polycrystalline MBE-grown GaAs for solar cells

    SciTech Connect (OSTI)

    Friedman, D. J.; Kurtz, Sarah R.; Kibbler, A. E.; Al-Jassim, M.; Jones, K.; Keyes, B.; Matson, R.

    1997-02-15

    This paper will discuss initial studies of thin-film GaAs grown by molecular-beam epitaxy for use in developing a thin-film GaAs solar cell. Photocurrent and photoluminescence intensity are related to the material morphology as a function of growth conditions. Growth temperature and V/III ratio have a dramatic effect on the photocurrent. However, it seems likely that even after optimizing such growth parameters, it will be necessary to provide substrates that can provide templates to enhance grain size from the start of thin-film growth.

  8. Highly transparent ammonothermal bulk GaN substrates

    SciTech Connect (OSTI)

    Jiang, WK; Ehrentraut, D; Downey, BC; Kamber, DS; Pakalapati, RT; Do Yoo, H; D'Evelyn, MP

    2014-10-01

    A novel apparatus has been employed to grow ammonothermal (0001) gallium nitride (GaN) with diameters up to 2 in The crystals have been characterized by x-ray diffraction rocking-curve (XRC) analysis, optical and scanning electron microscopy (SEM), cathodoluminescence (CL), and optical spectroscopy. High crystallinity GaN with FWHM values about 20-50 arcsec and dislocation densities below 1 x 10(5) cm(-2) have been obtained. High optical transmission was achieved with an optical absorption coefficient below 1 cm(-1) at a wavelength of 450 nm. (C) 2014 Elsevier B.V. All rights reserved.

  9. A hole modulator for InGaN/GaN light-emitting diodes Zi-Hui Zhang, Zabu Kyaw, Wei Liu, Yun Ji, Liancheng Wang, Swee Tiam Tan, Xiao Wei Sun, and Hilmi Volkan

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    well on optical power of light-emitting diodes Appl. Phys. Lett. 96, 051113 (2010); 10-emitting diodes (LEDs) due to the ineffective hole injection into the InGaN/GaN multiple quantum well (MQW) active in the p-GaN layer can be enhanced. Furthermore, the hole modulator is adopted in the InGaN/GaN LEDs, which

  10. $^{62}$Ni($n,?$) and $^{63}$Ni($n,?$) cross sections measured at n_TOF/CERN

    E-Print Network [OSTI]

    C. Lederer; C. Massimi; E. Berthoumieux; N. Colonna; R. Dressler; C. Guerrero; F. Gunsing; F. Käppeler; N. Kivel; M. Pignatari; R. Reifarth; D. Schumann; A. Wallner; S. Altstadt; S. Andriamonje; J. Andrzejewski; L. Audouin; M. Barbagallo; V. Becares; F. Becvar; F. Belloni; B. Berthier; J. Billowes; V. Boccone; D. Bosnar; M. Brugger; M. Calviani; F. Calvino; D. Cano-Ott; C. Carrapico; F. Cerutti; E. Chiaveri; M. Chin; G. Cortes; M. A. Cortes-Giraldo; I. Dillmann; C. Domingo-Pardo; I. Duran; N. Dzysiuk; C. Eleftheriadis; M. Fernandez-Ordonez; A. Ferrari; K. Fraval; S. Ganesan; A. R. Garc?a; G. Giubrone; M. B. Gomez-Hornillos; I. F. Goncalves; E. Gonzalez-Romero; F. Gramegna; E. Griesmayer; P. Gurusamy; S. Harrisopulos; M. Heil; K. Ioannides; D. G. Jenkins; E. Jericha; Y. Kadi; D. Karadimos; G. Korschinek; M. Krticka; J. Kroll; C. Langer; E. Lebbos; H. Leeb; L. S. Leong; R. Losito; M. Lozano; A. Manousos; J. Marganiec; S. Marrone; T. Martinez; P. F. Mastinu; M. Mastromarco; M. Meaze; E. Mendoza; A. Mengoni; P. M. Milazzo; F. Mingrone; M. Mirea; W. Mondalaers; C. Paradela; A. Pavlik; J. Perkowski; R. Plag; A. Plompen; J. Praena; J. M. Quesada; T. Rauscher; A. Riego; F. Roman; C. Rubbia; R. Sarmento; P. Schillebeeckx; S. Schmidt; G. Tagliente; J. L. Tain; D. Tarr?o; L. Tassan-Got; A. Tsinganis; L. Tlustos; S. Valenta; G. Vannini; V. Variale; P. Vaz; A. Ventura; M. J. Vermeulen; R. Versaci; V. Vlachoudis; R. Vlastou; T. Ware; M. Weigand; C. Weiß; T. J. Wright; P. Zugec

    2014-03-19

    The cross section of the $^{62}$Ni($n,\\gamma$) reaction was measured with the time-of-flight technique at the neutron time-of-flight facility n_TOF at CERN. Capture kernels of 42 resonances were analyzed up to 200~keV neutron energy and Maxwellian averaged cross sections (MACS) from $kT=5-100$ keV were calculated. With a total uncertainty of 4.5%, the stellar cross section is in excellent agreement with the the KADoNiS compilation at $kT=30$ keV, while being systematically lower up to a factor of 1.6 at higher stellar temperatures. The cross section of the $^{63}$Ni($n,\\gamma$) reaction was measured for the first time at n_TOF. We determined unresolved cross sections from 10 to 270 keV with a systematic uncertainty of 17%. These results provide fundamental constraints on $s$-process production of heavier species, especially the production of Cu in massive stars, which serve as the dominant source of Cu in the solar system.

  11. Strong enhancement of terahertz emission from GaAs in InAs/GaAs quantum dot structures

    SciTech Connect (OSTI)

    Estacio, Elmer; Pham, Minh Hong; Takatori, Satoru; Cadatal-Raduban, Marilou; Nakazato, Tomoharu; Shimizu, Toshihiko; Sarukura, Nobuhiko; Somintac, Armando; Defensor, Michael; Awitan, Fritz Christian B.; Jaculbia, Rafael B.; Salvador, Arnel; Garcia, Alipio

    2009-06-08

    We report on the intense terahertz emission from InAs/GaAs quantum dot (QD) structures grown by molecular beam epitaxy. Results reveal that the QD sample emission was as high as 70% of that of a p-type InAs wafer, the most intense semiconductor emitter to date. Excitation wavelength studies showed that the emission was due to absorption in strained undoped GaAs, and corresponds to a two order-of-magnitude enhancement. Moreover, it was found that multilayer QDs emit more strongly compared with a single layer QD sample. At present, we ascribe the intense radiation to huge strain fields at the InAs/GaAs interface.

  12. Characteristics of InGaP/InGaAs pseudomorphic high electron mobility transistors with triple delta-doped sheets

    SciTech Connect (OSTI)

    Chu, Kuei-Yi; Chiang, Meng-Hsueh Cheng, Shiou-Ying; Liu, Wen-Chau

    2012-02-15

    Fundamental and insightful characteristics of InGaP/InGaAs double channel pseudomorphic high electron mobility transistors (DCPHEMTs) with graded and uniform triple {delta}-doped sheets are coomprehensively studied and demonstrated. To gain physical insight, band diagrams, carrier densities, and direct current characteristics of devices are compared and investigated based on the 2D semiconductor simulator, Atlas. Due to uniform carrier distribution and high electron density in the double InGaAs channel, the DCPHEMT with graded triple {delta}-doped sheets exhibits better transport properties, higher and linear transconductance, and better drain current capability as compared with the uniformly triple {delta}-doped counterpart. The DCPHEMT with graded triple {delta}-doped structure is fabricated and tested, and the experimental data are found to be in good agreement with simulated results.

  13. Terahertz intersubband absorption in non-polar m-plane AlGaN/GaN quantum wells

    SciTech Connect (OSTI)

    Edmunds, C.; Malis, O.; Shao, J.; Shirazi-HD, M.; Manfra, M. J.

    2014-07-14

    We demonstrate THz intersubband absorption (15.6–26.1?meV) in m-plane AlGaN/GaN quantum wells. We find a trend of decreasing peak energy with increasing quantum well width, in agreement with theoretical expectations. However, a blue-shift of the transition energy of up to 14?meV was observed relative to the calculated values. This blue-shift is shown to decrease with decreasing charge density and is, therefore, attributed to many-body effects. Furthermore, a??40% reduction in the linewidth (from roughly 8 to 5?meV) was obtained by reducing the total sheet density and inserting undoped AlGaN layers that separate the wavefunctions from the ionized impurities in the barriers.

  14. High-performance broadband optical coatings on InGaN/GaN solar cells for multijunction device integration

    SciTech Connect (OSTI)

    Young, N. G. Farrell, R. M.; Iza, M.; Speck, J. S.; Perl, E. E.; Keller, S.; Bowers, J. E.; Nakamura, S.; DenBaars, S. P.

    2014-04-21

    We demonstrate InGaN/GaN multiple quantum well solar cells grown by metalorganic chemical vapor deposition on a bulk (0001) substrate with high-performance broadband optical coatings to improve light absorption. A front-side anti-reflective coating and a back-side dichroic mirror were designed to minimize front surface reflections across a broad spectral range and maximize rear surface reflections only in the spectral range absorbed by the InGaN, making the cells suitable for multijunction solar cell integration. Application of optical coatings increased the peak external quantum efficiency by 56% (relative) and conversion efficiency by 37.5% (relative) under 1 sun AM0 equivalent illumination.

  15. PT AND PT/NI "NEEDLE" ELETROCATALYSTS ON CARBON NANOTUBES WITH HIGH ACTIVITY FOR THE ORR

    SciTech Connect (OSTI)

    Colon-Mercado, H.

    2011-11-10

    Platinum and platinum/nickel alloy electrocatalysts supported on graphitized (gCNT) or nitrogen doped carbon nanotubes (nCNT) are prepared and characterized. Pt deposition onto carbon nanotubes results in Pt 'needle' formations that are 3.5 nm in diameter and {approx}100 nm in length. Subsequent Ni deposition and heat treatment results in PtNi 'needles' with an increased diameter. All Pt and Pt/Ni materials were tested as electrocatalysts for the oxygen reduction reaction (ORR). The Pt and Pt/Ni catalysts showed excellent performance for the ORR, with the heat treated PtNi/gCNT (1.06 mA/cm{sup 2}) and PtNi/nCNT (0.664 mA/cm{sup 2}) showing the highest activity.

  16. InGaAs/GaAsP strain balanced multi-quantum wires grown on misoriented GaAs substrates for high efficiency solar cells

    SciTech Connect (OSTI)

    Alonso-Álvarez, D.; Thomas, T.; Führer, M.; Hylton, N. P.; Ekins-Daukes, N. J.; Lackner, D.; Philipps, S. P.; Bett, A. W.; Sodabanlu, H.; Fujii, H.; Watanabe, K.; Sugiyama, M.; Nasi, L.; Campanini, M.

    2014-08-25

    Quantum wires (QWRs) form naturally when growing strain balanced InGaAs/GaAsP multi-quantum wells (MQW) on GaAs [100] 6° misoriented substrates under the usual growth conditions. The presence of wires instead of wells could have several unexpected consequences for the performance of the MQW solar cells, both positive and negative, that need to be assessed to achieve high conversion efficiencies. In this letter, we study QWR properties from the point of view of their performance as solar cells by means of transmission electron microscopy, time resolved photoluminescence and external quantum efficiency (EQE) using polarised light. We find that these QWRs have longer lifetimes than nominally identical QWs grown on exact [100] GaAs substrates, of up to 1??s, at any level of illumination. We attribute this effect to an asymmetric carrier escape from the nanostructures leading to a strong 1D-photo-charging, keeping electrons confined along the wire and holes in the barriers. In principle, these extended lifetimes could be exploited to enhance carrier collection and reduce dark current losses. Light absorption by these QWRs is 1.6 times weaker than QWs, as revealed by EQE measurements, which emphasises the need for more layers of nanostructures or the use light trapping techniques. Contrary to what we expected, QWR show very low absorption anisotropy, only 3.5%, which was the main drawback a priori of this nanostructure. We attribute this to a reduced lateral confinement inside the wires. These results encourage further study and optimization of QWRs for high efficiency solar cells.

  17. Thickness Effect of Al-Doped ZnO Window Layer on Damp Heat Stability of CuInGaSe2 Solar Cells: Preprint

    SciTech Connect (OSTI)

    Pern, F. J.; Mansfield, L.; DeHart, C.; Glick, S. H.; Yan, F.; Noufi, R.

    2011-07-01

    We investigated the damp heat (DH) stability of CuInGaSe2 (CIGS) solar cells as a function of thickness of the Al-doped ZnO (AZO) window layer from the 'standard' 0.12 ?m to a modest 0.50 ?m over an underlying 0.10-?m intrinsic ZnO buffer layer. The CIGS cells were prepared with external electrical contact using fine Au wire to the tiny 'standard' Ni/Al (0.05 ?m/3 ?m) metal grid contact pads. Bare cell coupons and sample sets encapsulated in a specially designed, Al-frame test structure with an opening for moisture ingress control using a TPT backsheet were exposed to DH at 85oC and 85% relative humidity, and characterized by current-voltage (I-V), quantum efficiency (QE), and (electrochemical) impedance spectroscopy (ECIS). The results show that bare cells exhibited rapid degradation within 50-100 h, accompanied by film wrinkling and delamination and corrosion of Mo and AlNi grid, regardless of AZO thickness. In contrast, the encapsulated cells did not show film wrinkling, delamination, and Mo corrosion after 168 h DH exposure; but the trend of efficiency degradation rate showed a weak correlation to the AZO thickness.

  18. Structural and Mössbauer spectroscopic study of Fe-Ni alloy nanoparticles

    SciTech Connect (OSTI)

    Kumar, Asheesh; Banerjee, S. Sudarsan, V.; Meena, S. S.

    2014-04-24

    Nano-crystalline Fe-Ni alloys have been synthesized in ethylene glycol medium. Based on XRD studies it is confirmed that, in these alloys Fe atoms are incorporated at Ni site to form Ni-Fe solid solutions. Mössbauer studies have established that for alloy particles having smaller size there is significant concentration of two different types of paramagnetic Fe species and their relative concentration decreased with increase in particle size.

  19. Prompt Proton Decay and Deformed Bands in 56Ni

    SciTech Connect (OSTI)

    Johansson, E. K.; Rudolph, D.; Andersson, L. L.; Torres, D. A.; Ragnarsson, I.; Andreoiu, C.; Baktash, Cyrus; Carpenter, M. P.; Charity, R. J.; Chiara, C. J.; Ekman, J.; Fahlander, C.; Hoel, C.; Pechenaya, O. L.; Reviol, W.; du Rietz, R.; Sarantites, D. G.; Seweryniak, D.; Sobotka, L. G.; Yu, Chang-Hong; Zhu, S.

    2008-06-01

    High-spin states in the doubly magic N=Z nucleus {sup 56}Ni have been investigated with three fusion-evaporation reaction experiments. New {gamma}-ray transitions are added, and a confirmation of a previously suggested prompt proton decay from a rotational band in {sup 56}Ni into the ground state of {sup 55}Co is presented. The rotational bands in {sup 56}Ni are discussed within the framework of cranked Nilsson-Strutinsky calculations.

  20. 1.9 kV AlGaN/GaN Lateral Schottky Barrier Diodes on Silicon

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

    Zhu, Mingda [University of Notre Dame, IN (United States); Song, Bo [Cornell University, Ithaca, NY (United States); Qi, Meng [University of Notre Dame, IN (United States); Hu, Zongyang [University of Notre Dame, IN (United States); Nomoto, Kazuki [University of Notre Dame, IN (United States); Yan, Xiaodong [University of Notre Dame, IN (United States); Cao, Yu [IQE, Westborough, MA (United States); Johnson, Wayne [IQE, Westborough, MA (United States); Kohn, Erhard [University of Notre Dame, IN (United States); Jena, Debdeep [Cornell University, Ithaca, NY (United States); Xing, Grace Huili [Cornell University, Ithaca, NY (United States)

    2015-04-01

    In this letter, we present AlGaN/GaN lateral Schottky barrier diodes on silicon with recessed anodes and dual field plates. A low specific on-resistance RON,SP (5.12 m?{center_dot}cm2), a low turn-on voltage (1.9 kV), were simultaneously achieved in devices with a 25 ?m anode/cathode separation, resulting in a power figure-of-merit (FOM) BV2/RON,SP of 727 MW{center_dot}cm2. The record high breakdown voltage of 1.9 kV is attributed to the dual field plate structure.

  1. Electrically pumped single-photon emission at room temperature from a single InGaN/GaN quantum dot

    SciTech Connect (OSTI)

    Deshpande, Saniya; Frost, Thomas; Hazari, Arnab; Bhattacharya, Pallab, E-mail: pkb@eecs.umich.edu [Center for Photonics and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Avenue, Ann Arbor, Michigan 48109 (United States)

    2014-10-06

    We demonstrate a semiconductor quantum dot based electrically pumped single-photon source operating at room temperature. Single photons emitted in the red spectral range from single In{sub 0.4}Ga{sub 0.6}N/GaN quantum dots exhibit a second-order correlation value g{sup (2)}(0) of 0.29, and fast recombination lifetime ?1.3 ±0.3 ns at room temperature. The single-photon source can be driven at an excitation repetition rate of 200?MHz.

  2. 1.9 kV AlGaN/GaN Lateral Schottky Barrier Diodes on Silicon

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

    Zhu, Mingda; Song, Bo; Qi, Meng; Hu, Zongyang; Nomoto, Kazuki; Yan, Xiaodong; Cao, Yu; Johnson, Wayne; Kohn, Erhard; Jena, Debdeep; et al

    2015-02-16

    In this letter, we present AlGaN/GaN lateral Schottky barrier diodes on silicon with recessed anodes and dual field plates. A low specific on-resistance RON,SP (5.12 m? · cm2), a low turn-on voltage (1.9 kV), were simultaneously achieved in devices with a 25 ?m anode/cathode separation, resulting in a power figure-of-merit (FOM) BV2/RON,SP of 727 MW·cm2. The record high breakdown voltage of 1.9 kV is attributed to the dual field plate structure.

  3. Ductile Ni[sub 3]Al alloys as bonding agents for ceramic materials

    DOE Patents [OSTI]

    Tiegs, T.N.; McDonald, R.R.

    1990-04-24

    An improved ceramic-metal composite is described comprising a mixture of a ceramic material with a ductile intermetallic alloy, preferably Ni[sub 3]Al. 2 figs.

  4. Ductile Ni.sub.3 Al alloys as bonding agents for ceramic materials in cutting tools

    DOE Patents [OSTI]

    Tiegs, Terry N. (Lenoir City, TN); McDonald, Robert R. (Traverse City, MI)

    1991-01-01

    An improved ceramic-metal composite comprising a mixture of a ceramic material with a ductile intermetallic alloy, preferably Ni.sub.3 Al.

  5. Ductile Ni[sub 3]Al alloys as bonding agents for ceramic materials in cutting tools

    DOE Patents [OSTI]

    Tiegs, T.N.; McDonald, R.R.

    1991-05-14

    An improved ceramic-metal composite comprising a mixture of a ceramic material with a ductile intermetallic alloy, preferably Ni[sub 3]Al is disclosed. 2 figures.

  6. Neutron Scattering of CeNi at the Spallation Neutron Source at...

    Office of Scientific and Technical Information (OSTI)

    Spallation Neutron Source at Oak Ridge National Laboratory: A Preliminary Report Citation Details In-Document Search Title: Neutron Scattering of CeNi at the Spallation Neutron...

  7. Strain mediated coupling in magnetron sputtered multiferroic PZT/Ni-Mn-In/Si thin film heterostructure

    SciTech Connect (OSTI)

    Singh, Kirandeep; Kaur, Davinder, E-mail: dkaurfph@iitr.ernet.in [Functional Nanomaterials Research Lab, Department of Physics and Centre of Nanotechnology, Indian Institute of Technology Roorkee, Roorkee-247667, Uttarakhand (India); Singh, Sushil Kumar [Functional Materials Division, Solid State Physics Lab (SSPL), DRDO, Lucknow Road, Timarpur, Delhi 110054 (India)

    2014-09-21

    The strain mediated electrical and magnetic properties were investigated in PZT/Ni-Mn-In heterostructure deposited on Si (100) by dc/rf magnetron sputtering. X-ray diffraction pattern revealed that (220) orientation of Ni-Mn-In facilitate the (110) oriented tertragonal phase growth of PZT layer in PZT/Ni-Mn-In heterostructure. A distinctive peak in dielectric constant versus temperature plots around martensitic phase transformation temperature of Ni-Mn-In showed a strain mediated coupling between Ni-Mn-In and PZT layers. The ferroelectric measurement taken at different temperatures exhibits a well saturated and temperature dependent P-E loops with a highest value of P{sub sat}~55 ?C/cm² obtained during martensite-austenite transition temperature region of Ni-Mn-In. The stress induced by Ni-Mn-In layer on upper PZT film due to structural transformation from martensite to austenite resulted in temperature modulated Tunability of PZT/Ni-Mn-In heterostructure. A tunability of 42% was achieved at 290 K (structural transition region of Ni-Mn-In) in these heterostructures. I-V measurements taken at different temperatures indicated that ohmic conduction was the main conduction mechanism over a large electric field range in these heterostructures. Magnetic measurement revealed that heterostructure was ferromagnetic at room temperature with a saturation magnetization of ~123 emu/cm³. Such multiferroic heterostructures exhibits promising applications in various microelectromechanical systems.

  8. Synthesis and Magnetic Properties of Ni-Zirconia Composites I. Zhitomirsky,* M. Niewczas, and A. Petric

    E-Print Network [OSTI]

    Niewczas, Marek

    Synthesis and Magnetic Properties of Ni-Zirconia Composites I. Zhitomirsky,* M. Niewczas, and A of the composites. Key Words: Electrodeposition; Hydrolysis; Polynuclear species; Zirconia; Nickel; Composite

  9. SF6432-NI Fixed Price Contracts with the Newly Independent States...

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

    CORPORATION SF 6432-NI (112015) SECTION II STANDARD TERMS AND CONDITIONS FOR FIXED PRICE CONTRACTS WITH THE NEWLY INDEPENDENT STATES OF THE FORMER SOVIET UNION THE FOLLOWING...

  10. Simple route for the synthesis of supercapacitive Co-Ni mixed hydroxide thin films

    SciTech Connect (OSTI)

    Dubal, D.P.; Department of Materials Science and Engineering, Gwangju Institute of Science and Technology, 261 Cheomdan-gwagiro, Buk-gu, Gwangju 500-712 ; Jagadale, A.D.; Patil, S.V.; Lokhande, C.D.

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer Novel method for deposition of Co-Ni mixed hydroxide. Black-Right-Pointing-Pointer Nanoparticle network of Co-Ni hydroxide. Black-Right-Pointing-Pointer High specific capacitance of 672 F g{sup -1}. Black-Right-Pointing-Pointer High discharge/charge rates. -- Abstract: Facile synthesis of Co-Ni mixed hydroxides films with interconnected nanoparticles networks through two step route is successfully established. These films have been characterized by X-ray diffraction (XRD), Fourier transform infrared technique (FTIR), scanning electron microscopy (SEM) and wettability test. Co-Ni film formation is confirmed from XRD and FTIR study. SEM shows that the surface of Co-Ni films is composed of interconnected nanoparticles. Contact angle measurement revealed the hydrophilic nature of films which is feasible for the supercapacitor. The electrochemical performance of the film is evaluated by cyclic voltammetry, and constant-current charge/discharge cycling techniques. Specific capacitance of the Co-Ni mixed hydroxide electrode achieved 672 F g{sup -1}. Impedance analysis shows that Co-Ni mixed hydroxide electrode provides less resistance for the intercalation and de-intercalation of ions. The Co-Ni mixed electrode exhibited good charge/discharge rate at different current densities. The results demonstrated that Co-Ni mixed hydroxide composite is very promising for the next generation high performance electrochemical supercapacitors.

  11. Theory of weak localization in ferromagnetic (Ga,Mn)As 

    E-Print Network [OSTI]

    Garate, Ion; Sinova, Jairo; Jungwirth, T.; MacDonald, A. H.

    2009-01-01

    We study quantum interference corrections to the conductivity in (Ga,Mn)As ferromagnetic semiconductors using a model with disordered valence-band holes coupled to localized Mn moments through a p-d kinetic-exchange interaction. We find that at Mn...

  12. Low-temperature magnetization of (Ga,Mn) As semiconductors 

    E-Print Network [OSTI]

    Jungwirth, T.; Masek, J.; Wang, KY; Edmonds, KW; Sawicki, M.; Polini, M.; Sinova, Jairo; MacDonald, AH; Campion, RP; Zhao, LX; Farley, NRS; Johal, TK; van der Laan, G.; Foxon, CT; Gallagher, BL.

    2006-01-01

    the semiphenomenological virtual crystal model the valence band holes experience a mean-field hMF =JpdNMn?S , and the band Hamiltonian can then be written as H? MF=H? KL?B?+hMFs?z, where H? KL?B? is the B-dependent six- band Kohn-Luttinger Hamiltonian of the GaAs host...

  13. Ohmic contacts for high-temperature GaP devices 

    E-Print Network [OSTI]

    Van der Hoeven, Willem Bernard

    1981-01-01

    in Table II, heat treatments have also been made by laser. One of the earliest papers that describe laser annealing to obtain ohmic contacts to GaP appeared in 1974 (20] . In this paper, Pounds, Saifi, and Hahm reported to have obtained ohmic contacts...

  14. High-quality InP on GaAs

    E-Print Network [OSTI]

    Quitoriano, Nathaniel Joseph

    2006-01-01

    In addition to traditional telecommunication applications, devices based on InP have received increased attention for high-performance electronics. InP growth on GaAs is motivated by the fact that InP wafers are smaller, ...

  15. Nanoscale GaAs metalsemiconductormetal photodetectors fabricated using nanoimprint lithography

    E-Print Network [OSTI]

    ­V) characteristics of the contacts are very sensi- tive to the surface states and defects. In this letter, we report mold with interdigited fin- gers was first created on a silicon substrate. Next, a layer of polymethylmethancrylate PMMA was spun on a semi- insulating SI GaAs substrate. Before imprinting, both the mold

  16. Properties of H, O and C in GaN

    SciTech Connect (OSTI)

    Pearton, S.J.; Abernathy, C.R.; Lee, J.W.

    1996-04-01

    The electrical properties of the light ion impurities H, O and C in GaN have been examined in both as-grown and implanted material. H is found to efficiently passivate acceptors such as Mg, Ca and C. Reactivation occurs at {ge} 450 C and is enhanced by minority carrier injection. The hydrogen does not leave the GaN crystal until > 800 C, and its diffusivity is relatively high ({approximately} 10{sup {minus}11} cm{sup 2}/s) even at low temperatures (< 200 C) during injection by wet etching, boiling in water or plasma exposure. Oxygen shows a low donor activation efficiency when implanted into GaN, with an ionization level of 30--40 meV. It is essentially immobile up to 1,100 C. Carbon can produce low p-type levels (3 {times} 10{sup 17} cm{sup {minus}3}) in GaN during MOMBE, although there is some evidence it may also create n-type conduction in other nitrides.

  17. Superior performance of Ni–W–Ce mixed-metal oxide catalysts for ethanol steam reforming: Synergistic effects of W- and Ni-dopants

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

    Liu, Zongyuan; Xu, Wenqian; Yao, Siyu; Johnson-Peck, Aaron C.; Zhao, Fuzhen; Michorczyk, Piotr; Kubacka, Anna; Stach, Eric A.; Fernández-García, Marcos; Senanayake, Sanjaya D.; et al

    2014-11-26

    In this study, the ethanol steam reforming (ESR) reaction was examined over a series of Ni-W-Ce oxide catalysts. The structures of the catalysts were characterized using in-situ techniques including X-ray diffraction, Pair Distribution Function, X-ray absorption fine structure and transmission electron microscopy; while possible surface intermediates for the ESR reaction were investigated by Diffuse Reflectance Infrared Fourier Transform Spectroscopy. In these materials, all the W and part of the Ni were incorporated into the CeO? lattice, with the remaining Ni forming highly dispersed nano NiO (more »under ESR conditions. The Ni-W-Ce systeme exhibited a much larger lattice strain than those seen for Ni-Ce and W-Ce. Synergistic effects between Ni and W inside ceria produced a substantial amount of defects and O vacancies that led to high catalytic activity, selectivity and stability (i.e. resistance to coke formation) during ethanol steam reforming.« less

  18. Luminescence properties of defects in GaN

    SciTech Connect (OSTI)

    Reshchikov, Michael A.; Morkoc, Hadis [Department of Electrical Engineering and Physics Department, Virginia Commonwealth University, Richmond, Virginia 23284 (United States)

    2005-03-15

    Gallium nitride (GaN) and its allied binaries InN and AIN as well as their ternary compounds have gained an unprecedented attention due to their wide-ranging applications encompassing green, blue, violet, and ultraviolet (UV) emitters and detectors (in photon ranges inaccessible by other semiconductors) and high-power amplifiers. However, even the best of the three binaries, GaN, contains many structural and point defects caused to a large extent by lattice and stacking mismatch with substrates. These defects notably affect the electrical and optical properties of the host material and can seriously degrade the performance and reliability of devices made based on these nitride semiconductors. Even though GaN broke the long-standing paradigm that high density of dislocations precludes acceptable device performance, point defects have taken the center stage as they exacerbate efforts to increase the efficiency of emitters, increase laser operation lifetime, and lead to anomalies in electronic devices. The point defects include native isolated defects (vacancies, interstitial, and antisites), intentional or unintentional impurities, as well as complexes involving different combinations of the isolated defects. Further improvements in device performance and longevity hinge on an in-depth understanding of point defects and their reduction. In this review a comprehensive and critical analysis of point defects in GaN, particularly their manifestation in luminescence, is presented. In addition to a comprehensive analysis of native point defects, the signatures of intentionally and unintentionally introduced impurities are addressed. The review discusses in detail the characteristics and the origin of the major luminescence bands including the ultraviolet, blue, green, yellow, and red bands in undoped GaN. The effects of important group-II impurities, such as Zn and Mg on the photoluminescence of GaN, are treated in detail. Similarly, but to a lesser extent, the effects of other impurities, such as C, Si, H, O, Be, Mn, Cd, etc., on the luminescence properties of GaN are also reviewed. Further, atypical luminescence lines which are tentatively attributed to the surface and structural defects are discussed. The effect of surfaces and surface preparation, particularly wet and dry etching, exposure to UV light in vacuum or controlled gas ambient, annealing, and ion implantation on the characteristics of the defect-related emissions is described.

  19. Testing a GaAs cathode in SRF gun

    SciTech Connect (OSTI)

    Wang, E.; Kewisch, J.; Ben-Zvi, I.; Burrill, A.; Rao, T.; Wu, Q.; Holmes, D.

    2011-03-28

    RF electron guns with a strained superlattice GaAs cathode are expected to generate polarized electron beams of higher brightness and lower emittance than do DC guns, due to their higher field gradient at the cathode's surface and lower cathode temperature. We plan to install a bulk GaAs:Cs in a SRF gun to evaluate the performance of both the gun and the cathode in this environment. The status of this project is: In our 1.3 GHz 1/2 cell SRF gun, the vacuum can be maintained at nearly 10{sup -12} Torr because of cryo-pumping at 2K. With conventional activation of bulk GaAs, we obtained a QE of 10% at 532 nm, with lifetime of more than 3 days in the preparation chamber and have shown that it can survive in transport from the preparation chamber to the gun. The beam line has been assembled and we are exploring the best conditions for baking the cathode under vacuum. We report here the progress of our test of the GaAs cathode in the SRF gun. Future particle accelerators, such as eRHIC and the ILC require high-brightness, high-current polarized electrons. Strained superlattice GaAs:Cs has been shown to be an efficient cathode for producing polarized electrons. Activation of GaAs with Cs,O(F) lowers the electron affinity and makes it energetically possible for all the electrons, excited into the conduction band that drift or diffuse to the emission surface, to escape into the vacuum. Presently, all operating polarized electron sources, such as the CEBAF, are DC guns. In these devices, the excellent ultra-high vacuum extends the lifetime of the cathode. However, the low field gradient on the photocathode's emission surface of the DC guns limits the beam quality. The higher accelerating gradients, possible in the RF guns, generate a far better beam. Until recently, most RF guns operated at room temperature, limiting the vacuum to {approx}10{sup -9} Torr. This destroys the GaAs's NEA surface. The SRF guns combine the excellent vacuum conditions of DC guns and the high accelerating gradient of the RF guns, potentially offering a long lived cathode with very low emittance. Testing this concept requires preparation of the cathode, transportation to the SRF gun and evaluation of the performance of the cathode and the gun at cryogenic temperatures. In our work at BNL, we successfully activated the bulk GaAs in the preparation chamber. The highest quantum efficient was 10% at 532 nm that fell to 0.5% after 100 hours. We explored three different ways to activate the GaAs. We verified that the GaAs photocathode remains stable for 30 hours in a 10{sup -11} Torr vacuum. Passing the photocathode through the low 10{sup -9} Torr transfer section in several seconds caused the QE to drop to 0.8%. The photocathode with 0.8% QE can be tested for the SRF gun. The gun and beam pipe were prepared and assembled. After baking at 200 C baking, the vacuum of the gun and beam pipe can sustain a low 10{sup -11} Torr at room temperature. The final test to extract electrons from the gun is ongoing. In this paper, we discuss our progress with this SRF gun and the results of the photocathode in preparation chamber and in magnet transfer line.

  20. Quaternary InGaAsSb Thermophotovoltaic Diodes

    SciTech Connect (OSTI)

    MW Dashiell; JF Beausang; H Ehsani; GJ Nichols; DM Depoy; LR Danielson; P Talamo; KD Rahner; EJ Brown; SR Burger; PM Foruspring; WF Topper; PF Baldasaro; CA Wang; R Huang; M Connors; G Turner; Z Shellenbarger; G Taylor; J Li; R Martinelli; D Donetski; S Anikeev; G Belenky; S Luryi

    2006-03-09

    In{sub x}Ga{sub 1-x}As{sub y}Sb{sub 1-y} thermophotovoltaic (TPV) diodes were grown lattice-matched to GaSb substrates by Metal Organic Vapor Phase Epitaxy (MOVPE) in the bandgap range of E{sub G} = 0.5 to 0.6eV. InGaAsSb TPV diodes, utilizing front-surface spectral control filters, are measured with thermal-to-electric conversion efficiency and power density of {eta}{sub TPV} = 19.7% and PD =0.58 W/cm{sup 2} respectively for a radiator temperature of T{sub radiator} = 950 C, diode temperature of T{sub diode} = 27 C, and diode bandgap of E{sub G} = 0.53eV. Practical limits to TPV energy conversion efficiency are established using measured recombination coefficients and optical properties of front surface spectral control filters, which for 0.53eV InGaAsSb TPV energy conversion is {eta}{sub TPV} = 28% and PD = 0.85W/cm{sup 2} at the above operating temperatures. The most severe performance limits are imposed by (1) diode open-circuit voltage (VOC) limits due to intrinsic Auger recombination and (2) parasitic photon absorption in the inactive regions of the module. Experimentally, the diode V{sub OC} is 15% below the practical limit imposed by intrinsic Auger recombination processes. Analysis of InGaAsSb diode electrical performance vs. diode architecture indicate that the V{sub OC} and thus efficiency is limited by extrinsic recombination processes such as through bulk defects.

  1. Remarkably reduced efficiency droop by using staircase thin InGaN quantum barriers in InGaN based blue light emitting diodes

    SciTech Connect (OSTI)

    Zhou, Kun; Ikeda, Masao, E-mail: mikeda2013@sinano.ac.cn, E-mail: jpliu2010@sinano.ac.cn; Liu, Jianping, E-mail: mikeda2013@sinano.ac.cn, E-mail: jpliu2010@sinano.ac.cn; Zhang, Shuming; Li, Deyao; Zhang, Liqun; Yang, Hui [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou (China); Key Laboratory of Nanodevices and Applications, Chinese Academy of Sciences, Suzhou (China); Cai, Jin; Wang, Hui; Wang, H. B. [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou (China); Key Laboratory of Nanodevices and Applications, Chinese Academy of Sciences, Suzhou (China); Suzhou Nanojoin Photonics Co., Ltd., Suzhou (China)

    2014-10-27

    The efficiency droop of InGaN/GaN(InGaN) multiple quantum well (MQW) light emitting diodes (LEDs) with thin quantum barriers (QB) is studied. With thin GaN QB (3?nm–6?nm thickness), the efficiency droop is not improved, which indicates that hole transport cannot be significantly enhanced by the thin GaN QBs. On the contrary, the efficiency droop was remarkably reduced by using a InGaN staircase QB (InGaN SC-QB) MQWs structure where InGaN SC-QBs lower the transport energy barrier of holes. The efficiency droop ratio was as low as 3.3% up to 200?A/cm{sup 2} for the InGaN SC-QB LED. By using monitoring QW with longer wavelength we observe a much uniform carrier distribution in the InGaN SC-QB LEDs, which reveals the mechanism of improvement in the efficiency droop.

  2. Effect of the accumulation of excess Ni atoms in the crystal structure of the intermetallic semiconductor n-ZrNiSn

    SciTech Connect (OSTI)

    Romaka, V. A.; Rogl, P.; Romaka, V. V.; Stadnyk, Yu. V.; Hlil, E. K.; Krajovskii, V. Ya.; Horyn, A. M.

    2013-07-15

    The crystal structure, electron density distribution, and energy, kinetic, and magnetic properties of the n-ZrNiSn intermetallic semiconductor heavily doped with a Ni impurity are investigated. The effect of the accumulation of an excess number of Ni{sub 1+x} atoms in tetrahedral interstices of the crystal structure of the semiconductor is found and the donor nature of such structural defects that change the properties of the semiconductor is established. The results obtained are discussed within the Shklovskii-Efros model of a heavily doped and strongly compensated semiconductor.

  3. The polygallides: Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub2}.

    SciTech Connect (OSTI)

    Peter, S. C.; Malliakas, C. D.; Nakotte, H.; Kothapilli, K.; Rayaprol, S.; Schultz, A. J.; Kanatzidis, M. G. (Materials Science Division); ( XSD); (Northwestern Univ.); (Jawaharlal Nehru Centre for Adv. Sci. Res.); (New Mexico State Univ.); (Los Alamos Nat. Lab.); (UGC-DAE Consortium for Sci. Res.)

    2012-03-01

    Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} were obtained from reactions of Yb and Ge in excess liquid gallium. The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} was refined using X-ray and neutron diffraction data on selected single crystals. Yb{sub 3}Ga{sub 7}Ge{sub 3} crystallizes in the monoclinic space group C2/c with lattice constants a = 12.2261(20) {angstrom}, b = 10.7447(20) {angstrom}, c = 8.4754(17) {angstrom} and {beta} = 110.288(30){sup o} (neutron diffraction data). The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} is an intergrowth of planar layers of YbGa{sub x}Ge{sub y} and puckered layers of (Ge)n. YbGa{sub 4}Ge{sub 2} crystallizes in a modified PuGa{sub 6} structure type in the tetragonal polar space group I4cm with lattice constants a = b = 5.9874(6) {angstrom} and c = 15.1178(19) {angstrom}. The structure of YbGa{sub 4}Ge{sub 2} is an intergrowth of puckered Ga layers and puckered Ga{sub x}Ge{sub y} layers with Yb atoms residing within the channels formed by the connection of the two layers. Physical properties, resistivity ({rho}), magnetic susceptibility ({chi}) and specific heat (C) were measured for Yb{sub 3}Ga{sub 7}Ge{sub 3}. No magnetic ordering was observed. It was found that at low temperatures, {rho} varied as T{sup 2} and C{alpha}T, indicating Fermi-liquid regime in Yb{sub 3}Ga{sub 7}Ge{sub 3} at low temperatures.

  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. Device-level thermal analysis of GaN-based electronics

    E-Print Network [OSTI]

    Bagnall, Kevin Robert

    2013-01-01

    Gallium nitride (GaN)-based microelectronics are one of the most exciting semiconductor technologies for high power density and high frequency electronics. The excellent electrical properties of GaN and its related alloys ...

  6. Light extraction in individual GaN nanowires on Si for LEDs

    E-Print Network [OSTI]

    Zhou, Xiang

    GaN-based nanowires hold great promise for solid state lighting applications because of their waveguiding properties and the ability to grow nonpolar GaN nanowire-based heterostructures, which could lead to increased light ...

  7. Inves&ga&ng the Trade-Off between Luminous Efficacy of Radia&on

    E-Print Network [OSTI]

    California at Davis, University of

    Inves&ga&ng the Trade-Off between Luminous Efficacy of Radia&on and Color, Canada · Lorne Whitehead, Canada #12;Inves&ga&ng the Trade-Off between Luminous

  8. Characterization of NIR InGaAs imager arrays for the JDEM SNAP mission concept

    E-Print Network [OSTI]

    2006-01-01

    Characterization of NIR InGaAs imager arrays for the JDEMapplications. Keywords: NIR, InGaAs, astronomy, low-1.7um band Near Infrared (NIR) focal plane mosaic with high

  9. Atomic structure of postgrowth annealed epitaxial Fe/(001)GaAs interfaces

    E-Print Network [OSTI]

    LeBeau, James; Hu, Qi O.; Palmstrom, Christopher; Stemmer, Susanne

    2008-01-01

    line pro?le across the interface along the line indicated inHAADF images of the GaAs/Fe interface along ?a? ?11 0? GaAsindicates the location of an interface step. Arrows in ?b?

  10. Plasmonic terahertz detectors based on a high-electron mobility GaAs/AlGaAs heterostructure

    SciTech Connect (OSTI)

    Bia?ek, M. Witowski, A. M.; Grynberg, M.; ?usakowski, J.; Orlita, M.; Potemski, M.; Czapkiewicz, M.; Umansky, V.

    2014-06-07

    In order to characterize magnetic field (B) tunable THz plasmonic detectors, spectroscopy experiments were carried out at liquid helium temperatures and high magnetic fields on devices fabricated on a high electron mobility GaAs/AlGaAs heterostructure. The samples were either gated (the gate of a meander shape) or ungated. Spectra of a photovoltage generated by THz radiation were obtained as a function of B at a fixed THz excitation from a THz laser or as a function of THz photon frequency at a fixed B with a Fourier spectrometer. In the first type of measurements, the wave vector of magnetoplasmons excited was defined by geometrical features of samples. It was also found that the magnetoplasmon spectrum depended on the gate geometry which gives an additional parameter to control plasma excitations in THz detectors. Fourier spectra showed a strong dependence of the magnetoplasmon resonance amplitude on the conduction-band electron filling factor which was explained within a model of the electron gas heating with THz radiation. The study allows to define both the advantages and limitations of plasmonic devices based on high-mobility GaAs/AlGaAs heterostructures for THz detection at low temperatures and high magnetic fields.

  11. On the redox origin of surface trapping in AlGaN/GaN high electron mobility transistors

    SciTech Connect (OSTI)

    Gao, Feng; Chen, Di; Tuller, Harry L.; Thompson, Carl V.; Palacios, Tomás

    2014-03-28

    Water-related redox couples in ambient air are identified as an important source of the surface trapping states, dynamic on-resistance, and drain current collapse in AlGaN/GaN high electron mobility transistors (HEMTs). Through in-situ X-ray photoelectron spectroscopy (XPS), direct signature of the water-related species—hydroxyl groups (OH) was found at the AlGaN surface at room temperature. It was also found that these species, as well as the current collapse, can be thermally removed above 200?°C in vacuum conditions. An electron trapping mechanism based on the H{sub 2}O/H{sub 2} and H{sub 2}O/O{sub 2} redox couples is proposed to explain the 0.5?eV energy level commonly attributed to the surface trapping states. Finally, the role of silicon nitride passivation in successfully removing current collapse in these devices is explained by blocking the water molecules away from the AlGaN surface.

  12. High 400?°C operation temperature blue spectrum concentration solar junction in GaInN/GaN

    SciTech Connect (OSTI)

    Zhao, Liang; Detchprohm, Theeradetch; Wetzel, Christian

    2014-12-15

    Transparent wide gap junctions suitable as high temperature, high flux topping cells have been achieved in GaInN/GaN by metal-organic vapor phase epitaxy. In structures of 25 quantum wells (QWs) under AM1.5G illumination, an open circuit voltage of 2.1?V is achieved. Of the photons absorbed in the limited spectral range of <450?nm, 64.2% are converted to electrons collected at the contacts under zero bias. At a fill factor of 45%, they account for a power conversion efficiency of38.6%. Under concentration, the maximum output power density per sun increases from 0.49?mW/cm{sup 2} to 0.51?mW/cm{sup 2} at 40?suns and then falls 0.42?mW/cm{sup 2} at 150?suns. Under external heating, a maximum of 0.59?mW/cm{sup 2} is reached at 250?°C. Even at 400?°C, the device is fully operational and exceeds room temperature performance. A defect analysis suggests that significantly higher fill factors and extension into longer wavelength ranges are possible with further development. The results prove GaInN/GaN QW solar junctions a viable and rugged topping cell for concentrator photovoltaics with minimal cooling requirements. By capturing the short range spectrum, they reduce the thermal load to any conventional cells stacked behind.

  13. Operating Characteristics of GaAs/InGaP Self Aligned Stripe Lasers Benjamin J. Stevens1

    E-Print Network [OSTI]

    quantum wells (QW)s,1) and InAs quantum dots at 1.3 mm2) have brought about the commercialization of Ga differential quantum efficiency, T-zero and far field as a function of stripe width. # 2009 The Japan Society offer a number of advantages over their InP counterparts, namely the use of larger substrates (>3 in

  14. Highly Ordered Ga Nanodroplets on a GaAs Surface Formed by a Focused Ion Beam Qiangmin Wei,1

    E-Print Network [OSTI]

    Lu, Wei

    quantum dots by low-energy ion sputtering on a surface has been reported in several semiconductor sys quantum dots on the surface. The mechanism involves the balance between roughening and smoothing actions], Ge [10], as well as a variety of III­V compounds (GaSb [11], InP [12], and InSb [13]) can form

  15. Comparison of electrostatic and localized plasmon induced light enhancement in hybrid InGaN/GaN quantum wells

    SciTech Connect (OSTI)

    Lin, Jie; Llopis, Antonio; Krokhin, Arkadii; Neogi, Arup, E-mail: arup@unt.edu [Department of Physics, University of North Texas, Denton, Texas 76203 (United States); Pereira, Sergio [CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Watson, Ian M. [SUPA, Institute of Photonics, University of Strathclyde, Glasgow (United Kingdom)

    2014-06-16

    The light enhancement phenomena in InGaN/GaN multi-quantum wells (MQWs) infiltrated with metal nanoparticles (NPs) are studied using resonant and off-resonant localized plasmon interactions. The emission and recombination characteristics of carriers in InGaN/GaN MQW structures with inverted hexagonal pits (IHPs) are modified distinctly depending on the nature of their interaction with the metal NPs and with the pumping and emitted photons. It is observed that the emission intensity of light is significantly enhanced when the emission energy is off-resonant to the localized plasmon frequency of the metal nanoparticles. This results in enhanced emission from MQW due to Au nanoparticles and from IHPs due to Ag nanoparticles. At resonant-plasmon frequency of the Ag NPs, the emission from MQWs is quenched due to the re-absorption of the emitted photons, or due to the drift carriers from c-plane MQWs towards the NPs because of the Coulomb forces induced by the image charge effect.

  16. Improved oxidation sulfidation resistance of Fe-Cr-Ni alloys

    DOE Patents [OSTI]

    Natesan, K.; Baxter, D.J.

    1983-07-26

    High temperature resistance of Fe-Cr-Ni alloy compositions to oxidative and/or sulfidative conditions is provided by the incorporation of about 1 to 8 wt % of Zr or Nb and results in a two-phase composition having an alloy matrix as the first phase and a fine grained intermetallic composition as the second phase. The presence and location of the intermetallic composition between grains of the matrix provides mechanical strength, enhanced surface scale adhesion, and resistance to corrosive attack between grains of the alloy matrix at temperatures of 500 to 1000/sup 0/C.

  17. Oxidation sulfidation resistance of Fe-Cr-Ni alloys

    DOE Patents [OSTI]

    Natesan, Ken (Naperville, IL); Baxter, David J. (Woodridge, IL)

    1984-01-01

    High temperature resistance of Fe-Cr-Ni alloy compositions to oxidative and/or sulfidative conditions is provided by the incorporation of about 1-8 wt. % of Zr or Nb and results in a two-phase composition having an alloy matrix as the first phase and a fine grained intermetallic composition as the second phase. The presence and location of the intermetallic composition between grains of the matrix provides mechanical strength, enhanced surface scale adhesion, and resistance to corrosive attack between grains of the alloy matrix at temperatures of 500.degree.-1000.degree. C.

  18. Stable atomic structure of NiTi austenite

    SciTech Connect (OSTI)

    Zarkevich, Nikolai A [Ames Laboratory; Johnson, Duane D [Ames Laboratory

    2014-08-01

    Nitinol (NiTi), the most widely used shape-memory alloy, exhibits an austenite phase that has yet to be identified. The usually assumed austenitic structure is cubic B2, which has imaginary phonon modes, hence it is unstable. We suggest a stable austenitic structure that “on average” has B2 symmetry (observed by x-ray and neutron diffraction), but it exhibits finite atomic displacements from the ideal B2 sites. The proposed structure has a phonon spectrum that agrees with that from neutron scattering, has diffraction spectra in agreement with x-ray diffraction, and has an energy relative to the ground state that agrees with calorimetry data.

  19. An analysis of the x-ray linear dichroism spectrum for NiO thin films grown on vicinal Ag(001)

    E-Print Network [OSTI]

    Wu, Y.Z.

    2008-01-01

    dichroism spectrum for NiO thin films grown on vicinal Ag(Antiferromagnetic (AFM) NiO thin films are grown epitaxiallyXLD). We find that the NiO AFM spin exhibits an in- plane

  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. GaN Initiative for Grid Applications (GIGA)

    SciTech Connect (OSTI)

    Turner, George

    2015-07-03

    For nearly 4 ½ years, MIT Lincoln Laboratory (MIT/LL) led a very successful, DoE-funded team effort to develop GaN-on-Si materials and devices, targeting high-voltage (>1 kV), high-power, cost-effective electronics for grid applications. This effort, called the GaN Initiative for Grid Applications (GIGA) program, was initially made up of MIT/LL, the MIT campus group of Prof. Tomas Palacios (MIT), and the industrial partner M/A Com Technology Solutions (MTS). Later in the program a 4th team member was added (IQE MA) to provide commercial-scale GaN-on-Si epitaxial materials. A basic premise of the GIGA program was that power electronics, for ubiquitous utilization -even for grid applications - should be closer in cost structure to more conventional Si-based power electronics. For a number of reasons, more established GaN-on-SiC or even SiC-based power electronics are not likely to reach theses cost structures, even in higher manufacturing volumes. An additional premise of the GIGA program was that the technical focus would be on materials and devices suitable for operating at voltages > 1 kV, even though there is also significant commercial interest in developing lower voltage (< 1 kV), cost effective GaN-on-Si devices for higher volume applications, like consumer products. Remarkable technical progress was made during the course of this program. Advances in materials included the growth of high-quality, crack-free epitaxial GaN layers on large-diameter Si substrates with thicknesses up to ~5 ?m, overcoming significant challenges in lattice mismatch and thermal expansion differences between Si and GaN in the actual epitaxial growth process. Such thick epilayers are crucial for high voltage operation of lateral geometry devices such as Schottky barrier (SB) diodes and high electron mobility transistors (HEMTs). New “Normally-Off” device architectures were demonstrated – for safe operation of power electronics circuits. The trade-offs between lateral and vertical devices were explored, with the conclusion that lateral devices are superior for fundamental thermal reasons, as well as for the demonstration of future generations of monolithic power circuits. As part of the materials and device investigations breakdown mechanisms in GaN-on-Si structures were fully characterized and effective electric field engineering was recognized as critical for achieving even higher voltage operation. Improved device contact technology was demonstrated, including the first gold-free metallizations (to enable processing in CMOS foundries) while maintaining low specific contact resistance needed for high-power operation and 5-order-of magnitude improvement in device leakage currents (essential for high power operation). In addition, initial GaN-on-Si epitaxial growth was performed on 8”/200 mm Si starting substrates.

  2. DISSERTATION ANTICIPATED PERFORMANCE OF Cu(In,Ga)Se2 SOLAR CELLS IN THE

    E-Print Network [OSTI]

    Sites, James R.

    i DISSERTATION ANTICIPATED PERFORMANCE OF Cu(In,Ga)Se2 SOLAR CELLS IN THE THIN-FILM LIMIT Submitted ENTITLED `ANTICIPATED PERFORMANCE OF Cu(In,Ga)Se2 SOLAR CELLS IN THE THIN-FILM LIMIT' BE ACCEPTED(In,Ga)Se2 SOLAR CELLS IN THE THIN-FILM LIMIT The demand for alternative sources of energy is rapidly

  3. 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

  4. Surface plasmon enhanced InGaN light emitter Koichi Okamoto*a

    E-Print Network [OSTI]

    Okamoto, Koichi

    is a very promising method for developing the super bright light emitting diodes (LEDs). Moreover, we foundGaN/GaN, light emitting diode, quantum well, internal quantum efficiency, solid-state light source 1. INTRODUCTION Since 1993, InGaN quantum wells (QW)-based light emitting diodes (LEDs) have been continuously

  5. Near perfect solar absorption in ultra-thin-film GaAs photonic crystals

    E-Print Network [OSTI]

    John, Sajeev

    Near perfect solar absorption in ultra-thin-film GaAs photonic crystals Sergey Eyderman,*a Alexei voltage of GaAs solar cells. The current world record for high efficiency solar cells is held by thin ultra-thin (GaAs in low-cost solar cells. However, this reduction in the volume

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

    E-Print Network [OSTI]

    Polman, Albert

    a non-concentrating system with limited emission angle in a thin, light trapping GaAs solar cellORIGINAL ARTICLE Highly efficient GaAs solar cells by limiting light emission angle Emily D Kosten1 of a high-quality GaAs solar cell is a feasible route to achieving power conversion efficiencies above 38

  7. Inversion of wurtzite GaN(0001) by exposure to V. Ramachandran and R. M. Feenstra

    E-Print Network [OSTI]

    Feenstra, Randall

    in the growth rate of GaN on different crystallographic planes [8], pointing to a surfactant effect of Mg on Ga in these films and the carrier concentration was therefore very low [1,2]; dopant activa- tion can be achieved of Mg at GaN growth temperatures is an issue and dopant in- corporation may be rather inefficient [5

  8. Ultrasensitive detection of Hg{sup 2+} using oligonucleotide-functionalized AlGaN/GaN high electron mobility transistor

    SciTech Connect (OSTI)

    Cheng, Junjie; Li, Jiadong; Miao, Bin; Wu, Dongmin; Wang, Jine; Pei, Renjun; Wu, Zhengyan

    2014-08-25

    An oligonucleotide-functionalized ion sensitive AlGaN/GaN high electron mobility transistor (HEMT) was fabricated to detect trace amounts of Hg{sup 2+}. The advantages of ion sensitive AlGaN/GaN HEMT and highly specific binding interaction between Hg{sup 2+} and thymines were combined. The current response of this Hg{sup 2+} ultrasensitive transistor was characterized. The current increased due to the accumulation of Hg{sup 2+} ions on the surface by the highly specific thymine-Hg{sup 2+}-thymine recognition. The dynamic linear range for Hg{sup 2+} detection has been determined in the concentrations from 10{sup ?14} to 10{sup ?8} M and a detection limit below 10{sup ?14} M level was estimated, which is the best result of AlGaN/GaN HEMT biosensors for Hg{sup 2+} detection till now.

  9. Deformations and magnetic rotations in the {sup 60}Ni nucleus

    SciTech Connect (OSTI)

    Torres, D. A.; Cristancho, F.; Andersson, L.-L.; Johansson, E. K.; Rudolph, D.; Fahlander, C.; Ekman, J.; Rietz, R. du; Andreoiu, C.; Carpenter, M. P.; Seweryniak, D.; Zhu, S.; Charity, R. J.; Chiara, C. J.; Hoel, C.; Pechenaya, O. L.; Reviol, W.; Sarantites, D. G.; Sobotka, L. G.; Baktash, C.

    2008-11-15

    Data from three experiments using the heavy-ion fusion evaporation-reaction {sup 36}Ar+{sup 28}Si have been combined to study high-spin states in the residual nucleus {sup 60}Ni, which is populated via the evaporation of four protons from the compound nucleus {sup 64}Ge. The GAMMASPHERE array was used for all the experiments in conjunction with a 4{pi} charged-particle detector arrays (MICROBALL, LUWUSIA) and neutron detectors (NEUTRON SHELL) to allow for the detection of {gamma} rays in coincidence with the evaporated particles. An extended {sup 60}Ni level scheme is presented, comprising more than 270{gamma}-ray transitions and 110 excited states. Their spins and parities have been assigned via directional correlations of {gamma} rays emitted from oriented states. Spherical shell-model calculations in the fp-shell characterize some of the low-spin states, while the experimental results of the rotational bands are analyzed with configuration-dependent cranked Nilsson-Strutinsky calculations.

  10. An inverted AlGaAs/GaAs patterned-Ge tunnel junction cascade concentrator solar cell. Final subcontract report, 1 January 1991--31 August 1992

    SciTech Connect (OSTI)

    Venkatasubramanian, R.

    1993-01-01

    This report describes work to develop inverted-grown Al{sub 0.34}Ga{sub 0.66}As/GaAs cascades. Several significant developments are reported on as follows: (1) The AM1.5 1-sun total-area efficiency of the top Al{sub 0.34}Ga{sub 0.66}As cell for the cascade was improved from 11.3% to 13.2% (NREL measurement [total-area]). (2) The ``cycled`` organometallic vapor phase epitaxy growth (OMVPE) was studied in detail utilizing a combination of characterization techniques including Hall-data, photoluminescence, and secondary ion mass spectroscopy. (3) A technique called eutectic-metal-bonding (EMB) was developed by strain-free mounting of thin GaAs-AlGaAs films (based on lattice-matched growth on Ge substrates and selective plasma etching of Ge substrates) onto Si carrier substrates. Minority-carrier lifetime in an EMB GaAs double-heterostructure was measured as high as 103 nsec, the highest lifetime report for a freestanding GaAs thin film. (4) A thin-film, inverted-grown GaAs cell with a 1-sun AM1.5 active-area efficiency of 20.3% was obtained. This cell was eutectic-metal-bonded onto Si. (5) A thin-film inverted-grown, Al{sub 0.34}Ga{sub 0.66}As/GaAs cascade with AM1.5 efficiency of 19.9% and 21% at 1-sun and 7-suns, respectively, was obtained. This represents an important milestone in the development of an AlGaAs/GaAs cascade by OMVPE utilizing a tunnel interconnect and demonstrates a proof-of-concept for the inverted-growth approach.

  11. Fabrication of NiTi shape memory alloy from elemental powders by hot isostatic pressing 

    E-Print Network [OSTI]

    McNeese, Matthew Doyle

    1997-01-01

    .0 and 50.6at.% Ni, packed and sealed into stainless steel containers, hot isostatically pressed (HIPed) at 20OMPa and 900-1050 'C, and machined to expose a gauge section of consolidated NiTi material for thennomechanical testing. Some samples of material...

  12. COMPARATIVE LIFE CYCLE ASSESSMENT OF ALCALINE CELLS AND NI-MH RECHARGEABLE BATTERIES

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    Page 1 COMPARATIVE LIFE CYCLE ASSESSMENT OF ALCALINE CELLS AND NI-MH RECHARGEABLE BATTERIES Jean by applying the LCA methodology to evaluate the environmental footprint of alkaline cells and Ni-MH batteries phase. Besides, the emphasis on rechargeable batteries is only justified from an environmental point

  13. Nanoscale compositional analysis of NiTi shape memory alloy films deposited by DC magnetron sputtering

    SciTech Connect (OSTI)

    Sharma, S. K.; Mohan, S.; Bysakh, S.; Kumar, A.; Kamat, S. V.

    2013-11-15

    The formation of surface oxide layer as well as compositional changes along the thickness for NiTi shape memory alloy thin films deposited by direct current magnetron sputtering at substrate temperature of 300 °C in the as-deposited condition as well as in the postannealed (at 600 °C) condition have been thoroughly studied by using secondary ion mass spectroscopy, x-ray photoelectron spectroscopy, and scanning transmission electron microscopy-energy dispersive x-ray spectroscopy techniques. Formation of titanium oxide (predominantly titanium dioxide) layer was observed in both as-deposited and postannealed NiTi films, although the oxide layer was much thinner (8 nm) in as-deposited condition. The depletion of Ti and enrichment of Ni below the oxide layer in postannealed films also resulted in the formation of a graded microstructure consisting of titanium oxide, Ni{sub 3}Ti, and B2 NiTi. A uniform composition of B2 NiTi was obtained in the postannealed film only below a depth of 200–250 nm from the surface. Postannealed film also exhibited formation of a ternary silicide (Ni{sub x}Ti{sub y}Si) at the film–substrate interface, whereas no silicide was seen in the as-deposited film. The formation of silicide also caused a depletion of Ni in the film in a region ?250–300 nm just above the film substrate interface.

  14. Method For Making Electronic Circuits Having Nial And Ni3al Substrates

    DOE Patents [OSTI]

    Deevi, Seetharama C. (Midlothian, VA); Sikka, Vinod K. (Oak Ridge, TN)

    2001-01-30

    A method for making electronic circuit component having improved mechanical properties and thermal conductivity comprises steps of providing NiAl and/or Ni.sub.3 Al, and forming an alumina layer thereupon prior to applying the conductive elements. Additional layers of copper-aluminum alloy or copper further improve mechanical strength and thermal conductivity.

  15. Dehydrogenation of Propane to Propylene over Supported Model NiAu Catalysts

    E-Print Network [OSTI]

    Goodman, Wayne

    Dehydrogenation of Propane to Propylene over Supported Model Ni­Au Catalysts Zhen Yan · Yunxi Yao 2012 Ó Springer Science+Business Media, LLC 2012 Abstract Hydrogenolysis and dehydrogenation of propane. For the conversionofpropane in the presence of hydrogen, the dehydrogenation of propane to propylene was observed onthe Ni

  16. Evolution of Graphene Growth on Ni and Cu by Carbon Isotope Labeling

    E-Print Network [OSTI]

    and acceptance by the semiconductor industry, Ni and Cu have received the most attention as a graphene substrateEvolution of Graphene Growth on Ni and Cu by Carbon Isotope Labeling Xuesong Li, Weiwei Cai, Luigi Instruments Incorporated, Dallas, Texas 75243 Received August 3, 2009 ABSTRACT Large-area graphene growth

  17. A Linear Combination Analyses Approach For Directly Speciating Ni Contaminated Soils.

    E-Print Network [OSTI]

    Sparks, Donald L.

    A Linear Combination Analyses Approach For Directly Speciating Ni Contaminated Soils. (S02-trivedi215458-Oral) Abstract: To provide an accurate description of the fate of Ni in aerial- contaminated soils to combine multiple analytical techniques to accurately determine metal speciation in complex soil systems

  18. Finite Element Based Micromechanical Analysis of Precipitated NiTi Shape Memory Alloys 

    E-Print Network [OSTI]

    Cox, Austin Edward

    2015-07-22

    into the material and its thermomechanical response than ever before. The most widely modeled and produced SMA class in industry today is one which hosts Ni as a core component of its composition, and usually takes the form of NiTi. When these SMA materials are heat...

  19. Ni-dispersed fullerenes: Hydrogen storage and desorption properties Weon Ho Shin and Seong Ho Yang

    E-Print Network [OSTI]

    Goddard III, William A.

    Ni-dispersed fullerenes: Hydrogen storage and desorption properties Weon Ho Shin and Seong Ho Yang could be viable alternatives to reversible hydrogen storage. It is demonstrated that a single Ni coated-dispersed fullerenes are considered to be the novel hydrogen storage media capable of storing 6.8 wt % H2, thus

  20. Biomaterials 24 (2003) 39313939 Corrosion and wear-corrosion behavior of NiTi modified

    E-Print Network [OSTI]

    Crone, Wendy C.

    2003-01-01

    Biomaterials 24 (2003) 3931­3939 Corrosion and wear-corrosion behavior of NiTi modified by plasma, aerospace, and automotive industries. NiTi alloys are important materials for biomedical and dental devices. The alloy has been used for making orthodontic dental arch wires and medical guide wires for diagnostic

  1. Effect of Mo Addition on Structure and Magnetocaloric Effect in c-FeNi Nanocrystals

    E-Print Network [OSTI]

    Laughlin, David E.

    - tion metals have been investigated to replace rare- earth metals for cost reduction. Researchers have comparable to those of rare-earth metals. Recently, Fe-Ni alloys were suggested as economical alterna- tives3 refrigerants without critical rare-earth materials. Key words: Nanostructured FeNi, magnetocaloric effect

  2. Superelastic and cyclic response of NiTi SMA at various strain rates and temperatures

    E-Print Network [OSTI]

    Nemat-Nasser, Sia

    in the range of 77­400 K. The influence of the annealing temperature on the fatigue response is also examined of NiTi SMAs depend on the annealing temperature; (2) in cyclic loading, the dissipated energy over loading rates, NiTi SMAs show properties similar to ordinary steels, as has been established by the first

  3. Formation and Stability of Ni-Al Hydroxide Phases in Soils

    E-Print Network [OSTI]

    Sparks, Donald L.

    surface precipitate phases on kaolinite surfaces as the humic acid content of the system was increased. At 1% humic acid by weight, mixed Ni-Al hydroxide precipitates formed on the kaolinite surface after 4 days. At 5 wt % humic acid, however, precipitate formation was slower and resulted in Ni(OH)2

  4. Bilayer thickness effects on nanoindentation behavior of Ag/Ni multilayers

    E-Print Network [OSTI]

    Hong, Soon Hyung

    by nanoindentation hardness and creep tests. The hardness increased with decreasing bilayer thickness, although of nanoindentation creep tests on Ag/Ni nanomultilayers with various bilayer thicknesses. Multilayered Ag/Ni films thickness. A nanoindentation creep test was used to study the creep behavior of nano- scale multilayers

  5. THREE-DIMENSIONAL ATOMIC STRUCTURE OF NiO ZrO2(CUBIC) INTERFACES

    E-Print Network [OSTI]

    Pennycook, Steve

    THREE-DIMENSIONAL ATOMIC STRUCTURE OF NiO± ZrO2(CUBIC) INTERFACES E. C. DICKEY{1 , V. P. DRAVID1-dimensional atomic structure of low-energy NiO±ZrO2(cubic) interfaces is determined through a combination of electron the structural and chemical aspects of the interface and associ- ated interfacial relaxation mechaubic) interface

  6. Ferromagnetic interactions and martensitic transformation in Fe doped Ni-Mn-In shape memory alloys

    SciTech Connect (OSTI)

    Lobo, D. N.; Priolkar, K. R.; Emura, S.; Nigam, A. K.

    2014-11-14

    The structure, magnetic, and martensitic properties of Fe doped Ni-Mn-In magnetic shape memory alloys have been studied by differential scanning calorimetry, magnetization, resistivity, X-ray diffraction (XRD), and EXAFS. While Ni{sub 2}MnIn{sub 1?x}Fe{sub x} (0???x???0.6) alloys are ferromagnetic and non martensitic, the martensitic transformation temperature in Ni{sub 2}Mn{sub 1.5}In{sub 1?y}Fe{sub y} and Ni{sub 2}Mn{sub 1.6}In{sub 1?y}Fe{sub y} increases for lower Fe concentrations (y???0.05) before decreasing sharply for higher Fe concentrations. XRD analysis reveals presence of cubic and tetragonal structural phases in Ni{sub 2}MnIn{sub 1?x}Fe{sub x} at room temperature with tetragonal phase content increasing with Fe doping. Even though the local structure around Mn and Ni in these Fe doped alloys is similar to martensitic Mn rich Ni-Mn-In alloys, presence of ferromagnetic interactions and structural disorder induced by Fe affect Mn-Ni-Mn antiferromagnetic interactions resulting in suppression of martensitic transformation in these Fe doped alloys.

  7. The Influence of Ni-Coated TiC on Laser-Deposited IN625 Metal Matrix Composites

    E-Print Network [OSTI]

    2010-01-01

    The In?uence of Ni-Coated TiC on Laser-Deposited IN625 Metalwith Ni-coated and uncoated TiC reinforcement particles toand spatial distribution of TiC particles in the deposited

  8. Direct synthesis of porous NiO nanowall arrays on conductive substrates for supercapacitor application

    SciTech Connect (OSTI)

    Zhu, Jianhui; Jiang, Jian; Liu, Jingping; Ding, Ruimin; Ding, Hao; Feng, Yamin; Wei, Guangming; Huang, Xintang

    2011-03-15

    Porous NiO nanowall arrays (NWAs) grown on flexible Fe-Co-Ni alloy have been successfully synthesized by using nullaginite (Ni{sub 2}(OH){sub 2}CO{sub 3}) as precursor and investigated as supercapacitor electrodes. In details, we adopted a simple hydrothermal method to realize Ni{sub 2}(OH){sub 2}CO{sub 3} NWAs and examined their robust mechanical adhesion to substrate via a long-time ultrasonication test. Porous NiO NWAs were then obtained by a post-calcination towards precursors at 500 {sup o}C in nitrogen atmosphere. Electrochemical properties of as-synthesized NiO NWAs were evaluated by cyclic voltammetry and galvanostatic charge/discharge; porous NiO NWAs electrode delivered a specific capacitance of 270 F/g (0.67 A/g); even at high current densities, the electrode could still deliver a high capacitance up to 236 F/g (13.35 A/g). Meanwhile, it exhibited excellent cycle lifetime with {approx}93% specific capacitance kept after 4000 cycles. These results suggest that as-made porous NiO NWAs electrode is a promising candidate for future thin-film supercapacitors and other microelectronic systems. -- Graphical abstract: Porous NiO nanowall arrays (NWAs) grown on alloy substrate have been made using nullaginite as precursor and studied as supercapacitor electrodes. Porous nanowalls interconnected with each other resulting in the formation of extended-network architectures and exhibited excellent capacitor properties. NiO NWAs electrode delivered a capacitance of 270 F/g (0.67 A/g); even at high current density, the electrode could still deliver a high capacitance up to 236 F/g (13.35 A/g). Besides, it exhibited excellent cycle lifetime with {approx}93% capacitance kept after 4000 cycles. These remarkable results made it possible for mass production of NiO NWAs and future thin-film microelectronic applications. Display Omitted Research highlights: {yields} Large-scale nullaginite (Ni{sub 2}(OH){sub 2}CO{sub 3}) nanowall arrays (NWAs) have been synthesized on flexible alloy substrate by a facile hydrothermal method. {yields} Ultrasonication test has been conducted to demonstrate the robust mechanical adhesion between NWAs and substrate. {yields} As supercapacitor electrodes porous NiO NWAs obtained by a post-calcination towards Ni{sub 2}(OH){sub 2}CO{sub 3} precursors have exhibited excellent electrochemical properties.

  9. Nanoscale selective area growth of thick, dense, uniform, In-rich, InGaN nanostructure arrays on GaN/sapphire template

    SciTech Connect (OSTI)

    Sundaram, S.; El Gmili, Y.; Bonanno, P. L. [CNRS, UMI 2958 Georgia Tech - CNRS, 57070 Metz (France); Puybaret, R.; Li, X.; Voss, P. L.; Ougazzaden, A. [Georgia Institute of Technology, UMI 2958 Georgia Tech - CNRS, 57070 Metz (France); Pantzas, K.; Patriarche, G. [CNRS, UPR LPN, Route de Nozay, 91460 Marcoussis (France); Orsal, G.; Salvestrini, J. P., E-mail: salvestr@metz.supelec.fr [Université de Lorraine, Supélec, LMOPS, EA4423, 57070 Metz (France); Troadec, D. [Université des Sciences et Technologies de Lille, CNRS, UMR 8520 IEMN, 59000 Lille (France); Cai, Z.-H. [Advanced Photon Source, 9700 S. Cass Avenue, Argonne, Illinois 60439 (United States)

    2014-10-28

    Uniform, dense, single-phase, 150?nm thick indium gallium nitride (InGaN) nanostructure (nanorods and nanostripes) arrays have been obtained on gallium nitride templates, by metal organic chemical vapor deposition and nanoscale selective area growth on silicon dioxide patterned masks. The 150?nm thick InGaN nanorods have a perfect hexagonal pyramid shape with relatively homogenous indium concentration up to 22%, which is almost twice as high as in planar InGaN grown in the same condition, and luminesce at 535?nm. InGaN nanostripes feature c-axis oriented InGaN in the core which is covered by InGaN grown along semi-polar facets with higher In content. Transmission electron microscope and sub micron beam X-rays diffraction investigations confirm that both InGaN nanostructures are mostly defect free and monocrystalline. The ability to grow defect-free thick InGaN nanostructures with reduced polarization and high indium incorporation offers a solution to develop high efficiency InGaN-based solar cells.

  10. Understanding and engineering of NiGe/Ge junction formed by phosphorus ion implantation after germanidation

    SciTech Connect (OSTI)

    Oka, Hiroshi, E-mail: oka@asf.mls.eng.osaka-u.ac.jp; Minoura, Yuya; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji [Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan)

    2014-08-11

    Modulation of the effective electron Schottky barrier height (eSBH) of NiGe/Ge contacts induced by phosphorus ion implantation after germanide formation was investigated by considering local inhomogeneity in the eSBH. Systematic studies of NiGe/Ge contact devices having various germanide thicknesses and ion implantation areas indicated the threshold dopant concentration at the NiGe/Ge interface required for eSBH modulation and negligible dopant diffusion even at NiGe/Ge interface during drive-in annealing, leading to variation in the eSBH between the bottom and sidewall portions of the NiGe regions. Consequently, this method makes it possible to design source/drain contacts with low-resistivity Ohmic and ideal rectifying characteristics for future Ge-based transistors.

  11. Thermal plasma synthesis of Fe{sub 1?x}Ni{sub x} alloy nanoparticles

    SciTech Connect (OSTI)

    Raut, Suyog A.; Kanhe, Nilesh S.; Bhoraskar, S. V.; Mathe, V. L.; Das, A. K.

    2014-04-24

    Fe-Ni alloy nanoparticles are of great interest because of diverse practical applications in the fields such as magnetic fluids, high density recording media, catalysis and medicine. We report the synthesis of Fe-Ni nanoparticles via thermal plasma route. Thermal plasma assisted synthesis is a high temperature process and gives high yields of production. Here, we have used direct arc thermal plasma plume of 6kw as a source of energy at operating pressure 500 Torr. The mixture of Fe-Ni powder in required proportion (Fe{sub 1?x}Ni{sub x}; x=0.30, 0.32, 0.34, 0.36, 0.38 and 0.40) was made to evaporate simultaneously from the graphite anode in thermal plasma reactor to form Fe-Ni bimetallic nanoparticles. The as synthesized particles were characterized by X-Ray Diffraction (XRD), Thermo-Gravimetric Analysis/Differential Scanning Calorimtry (TGA/DSC)

  12. Electrochemical sensing behaviour of Ni doped Fe{sub 3}O{sub 4} nanoparticles

    SciTech Connect (OSTI)

    Suresh, R.; Giribabu, K.; Manigandan, R.; Narayanan, V., E-mail: vnnara@yahoo.co.in [Department of Inorganic Chemistry, University of Madras, Guindy Campus, Chennai 600 025 (India); Vijayalakshmi, L. [Annai Veilankanni's College for Women (Arts and Science), Saidapet, Chennai 600015 (India); Stephen, A. [Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600 025 (India)

    2014-01-28

    Ni doped Fe{sub 3}O{sub 4} nanoparticles were synthesized by simple hydrothermal method. The prepared nanomaterials were characterized by X-ray diffraction analysis, DRS-UV-Visible spectroscopy and field emission scanning electron microscopy. The XRD confirms the phase purity of the synthesized Ni doped Fe{sub 3}O{sub 4} nanoparticles. The optical property of Ni doped Fe{sub 3}O{sub 4} nanoparticles were studied by DRS UV-Visible analysis. The electrochemical sensing property of pure and Ni doped Fe{sub 3}O{sub 4} nanoparticles were examined using uric acid as an analyte. The obtained results indicated that the Ni doped Fe{sub 3}O{sub 4} nanoparticles exhibited higher electrocatalytic activity towards uric acid.

  13. Eutectic bonding of a Ti sputter coated, carbon aerogel wafer to a Ni foil

    SciTech Connect (OSTI)

    Jankowski, A.F.; Hayes, J.P.; Kanna, R.L.

    1994-06-01

    The formation of high energy density, storage devices is achievable using composite material systems. Alternate layering of carbon aerogel wafers and Ni foils with rnicroporous separators is a prospective composite for capacitor applications. An inherent problem exists to form a physical bond between Ni and the porous carbon wafer. The bonding process must be limited to temperatures less than 1000{degrees}C, at which point the aerogel begins to degrade. The advantage of a low temperature eutectic in the Ni-Ti alloy system solves this problem. Ti, a carbide former, is readily adherent as a sputter deposited thin film onto the carbon wafer. A vacuum bonding process is then used to join the Ni foil and Ti coating through eutectic phase formation. The parameters required for successfld bonding are described along with a structural characterization of the Ni foil-carbon aerogel wafer interface.

  14. Fabrication of NiO thin film electrode for supercapacitor applications

    SciTech Connect (OSTI)

    Mali, V. V.; Navale, S. T.; Chougule, M. A.; Khuspe, G. D.; Godse, P. R.; Patil, V. B., E-mail: drvbpatil@gmail.com [Functional Materials Research Laboratory, School of Physical Sciences, Solapur University, Solapur-413255 (India); Pawar, S. A. [Department of Electronics, Shri Shivaji Mahavidhyala, Barshi, Solapur-413411 (India)

    2014-04-24

    Nanocrystalline NiO electrode is successfully electrosynthesized for supercapacitor application. The nanocrystalline NiO electrode is characterized using scanning electron microscope (SEM). Nickel oxide is a highly porous and the film surface looked smooth and composed of fine elongated particles. The supercapacitive performance of NiO electrode is tested using cyclic voltammetry (C-V) technique in 0.5M Na{sub 2}S{sub 2}O{sub 3} electrolyte within potential range of ?1.2 to +1.2 V. The effect of scan rate on the capacitance of NiO electrode is studied. The highest specific capacitance of 439 Fg{sup ?1} at the voltage scan rate of 50mVs{sup ?1} is achieved. Additionally stability and charging–discharging of NiO electrode are studied.

  15. Monodisperse core/shell Ni/FePt nanoparticles and their con-version to Ni/Pt to catalyze oxygen reduction

    SciTech Connect (OSTI)

    Zhang, Sen; Su, Dong; Doan-Nguyen, Vicky V. T.; Wu, Yaoting; Li, Jing; Sun, Shouheng; Murray, Christopher B.; Hao, Yizhou

    2014-11-12

    We report a size-controllable synthesis of monodisperse core/shell Ni/FePt nanoparticles (NPs) via a seed-mediated growth and their subsequent conversion to Ni/Pt NPs. Preventing surface oxidation of the Ni seeds is essential for the growth of uniform FePt shells. These Ni/FePt NPs have a thin (? 1 nm) FePt shell, and can be converted to Ni/Pt by acetic acid wash to yield active catalysts for oxygen reduction reaction (ORR). Tuning the core size allow for optimization of their electrocatalytic activity. The specific activity and mass activity of 4.2 nm/0.8 nm core/shell Ni/FePt reach 1.95 mA/cm² and 490 mA/mgPt at 0.9 V (vs. reversible hydrogen electrode, RHE), which are much higher than those of benchmark commercial Pt catalyst (0.34 mA/cm² and 92 mA/mgPt at 0.9 V). Our studies provide a robust approach to monodisperse core/shell NPs with non-precious metal core, making it possible to develop advanced NP catalysts with ultralow Pt content for ORR and many other heterogeneous reactions.

  16. An APFIM and TEM study of Ni{sub 4}Mo precipitation in a commercial Ni-28% Mo-1.4% Fe-0.4% Cr wt. % alloy

    SciTech Connect (OSTI)

    Thomson, R.C.; Brown, N.; Bates, J.S. [Loughborough Univ. (United Kingdom). Inst. of Polymer Technology and Materials Engineering; Russell, K.F.; Miller, M.K. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

    1998-02-01

    Ni-Mo alloys containing at least 26 wt.% Mo have a negligible corrosion rate in boiling 10% hydrochloric acid and are therefore used in corrosive environments. A series of commercial Ni-Mo alloys has been developed with subtle variations in chemical composition. These alloys usually contain {approximately} 28 wt.% Mo with additions of up to 5% Fe and Cr. A significant amount of research has been performed to understand the microstructure and properties of these alloys, although most of the effort has concentrated on the Ni-Mo binary system. In some alloys with low Fe and Cr contents, a severe embrittlement problem has been observed due to the formation of the Ni{sub 4}Mo (D1{sub a}-ordered) phase within the microstructure. This research focuses on a commercial alloy with nominal composition Ni-28% Mo-1.4% Fe-0.4% Cr-0.1% Mn-0.003 wt.% C. The material supplied was a heat treatment coupon which had been attached to a large vessel during fabrication. Assessment of the chemical analysis of the alloy suggested that detrimental phases could be present or might appear during subsequent repair work. Therefore, it was important to assess the microstructural condition of the vessel, and in particular the kinetics of precipitation of Ni{sub 4}Mo.

  17. Correlating Extent of Pt–Ni Bond Formation with Low-temperature Hydrogenation of Benzene and 1,3-butadiene over Supported Pt/Ni Bimetallic Catalysts

    SciTech Connect (OSTI)

    Lonergan, W.; Vlachos, D; Chen, J

    2010-01-01

    Low-temperature hydrogenation of benzene and 1,3-butadiene on supported Pt/Ni catalysts have been used as probe reactions to correlate hydrogenation activity with the extent of Pt-Ni bimetallic bond formation. Pt/Ni bimetallic and Pt and Ni monometallic catalysts were supported on {gamma}-Al{sub 2}O{sub 3} using incipient wetness impregnation. Two sets of bimetallic catalysts were synthesized: one set to study the effect of metal atomic ratio and the other to study the effect of impregnation sequence. Fourier transform infrared spectroscopy (FTIR) CO adsorption studies were performed to characterize the surface composition of the bimetallic nanoparticles, and transmission electron microscopy (TEM) was utilized to characterize the particle size distribution. Batch reactor studies with FTIR demonstrated that all bimetallic catalysts outperformed monometallic catalysts for both benzene and 1,3-butadiene hydrogenation. Within the two sets of bimetallic catalysts, it was found that catalysts with a smaller Pt:Ni ratio possessed higher hydrogenation activity and that catalysts synthesized using co-impregnation had greater activity than sequentially impregnated catalysts. Extended X-ray absorption fine structure (EXAFS) measurements were performed in order to verify the extent of Pt-Ni bimetallic bond formation, which was found to correlate with the hydrogenation activity.

  18. Monodisperse core/shell Ni/FePt nanoparticles and their con-version to Ni/Pt to catalyze oxygen reduction

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

    Zhang, Sen [Univ. of Pennsylvania, Philadelphia, PA (United States); Su, Dong [Brookhaven National Lab. (BNL), Upton, NY (United States); Doan-Nguyen, Vicky V. T. [Univ. of Pennsylvania, Philadelphia, PA (United States); Wu, Yaoting [Univ. of Pennsylvania, Philadelphia, PA (United States); Li, Jing [Brookhaven National Lab. (BNL), Upton, NY (United States); Sun, Shouheng [Brown Univ., Providence, RI (United States); Murray, Christopher B. [Univ. of Pennsylvania, Philadelphia, PA (United States); Hao, Yizhou [Univ. of Pennsylvania, Philadelphia, PA (United States)

    2014-11-12

    We report a size-controllable synthesis of monodisperse core/shell Ni/FePt nanoparticles (NPs) via a seed-mediated growth and their subsequent conversion to Ni/Pt NPs. Preventing surface oxidation of the Ni seeds is essential for the growth of uniform FePt shells. These Ni/FePt NPs have a thin (? 1 nm) FePt shell, and can be converted to Ni/Pt by acetic acid wash to yield active catalysts for oxygen reduction reaction (ORR). Tuning the core size allow for optimization of their electrocatalytic activity. The specific activity and mass activity of 4.2 nm/0.8 nm core/shell Ni/FePt reach 1.95 mA/cm² and 490 mA/mgPt at 0.9 V (vs. reversible hydrogen electrode, RHE), which are much higher than those of benchmark commercial Pt catalyst (0.34 mA/cm² and 92 mA/mgPt at 0.9 V). Our studies provide a robust approach to monodisperse core/shell NPs with non-precious metal core, making it possible to develop advanced NP catalysts with ultralow Pt content for ORR and many other heterogeneous reactions.

  19. Monodisperse core/shell Ni/FePt nanoparticles and their con-version to Ni/Pt to catalyze oxygen reduction

    SciTech Connect (OSTI)

    Zhang, Sen; Hao, Yizhou; Su, Dong; Doan-Nguyen, Vicky V. T.; Wu, Yaoting; Li, Jing; Sun, Shouheng; Murray, Christopher B.

    2014-10-28

    We report a size-controllable synthesis of monodisperse core/shell Ni/FePt nanoparticles (NPs) via a seed-mediated growth and their subsequent conversion to Ni/Pt NPs. Preventing surface oxidation of the Ni seeds is essential for the growth of uniform FePt shells. These Ni/FePt NPs have a thin (? 1 nm) FePt shell, and can be converted to Ni/Pt by acetic acid wash to yield active catalysts for oxygen reduction reaction (ORR). Tuning the core size allow for optimization of their electrocatalytic activity. The specific activity and mass activity of 4.2 nm/0.8 nm core/shell Ni/FePt reach 1.95 mA/cm² and 490 mA/mgPt at 0.9 V (vs. reversible hydrogen electrode, RHE), which are much higher than those of benchmark commercial Pt catalyst (0.34 mA/cm² and 92 mA/mgPt at 0.9 V). Our studies provide a robust approach to monodisperse core/shell NPs with non-precious metal core, making it possible to develop advanced NP catalysts with ultralow Pt content for ORR and many other heterogeneous reactions.

  20. Monodisperse core/shell Ni/FePt nanoparticles and their con-version to Ni/Pt to catalyze oxygen reduction

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

    Zhang, Sen; Hao, Yizhou; Su, Dong; Doan-Nguyen, Vicky V. T.; Wu, Yaoting; Li, Jing; Sun, Shouheng; Murray, Christopher B.

    2014-10-28

    We report a size-controllable synthesis of monodisperse core/shell Ni/FePt nanoparticles (NPs) via a seed-mediated growth and their subsequent conversion to Ni/Pt NPs. Preventing surface oxidation of the Ni seeds is essential for the growth of uniform FePt shells. These Ni/FePt NPs have a thin (? 1 nm) FePt shell, and can be converted to Ni/Pt by acetic acid wash to yield active catalysts for oxygen reduction reaction (ORR). Tuning the core size allow for optimization of their electrocatalytic activity. The specific activity and mass activity of 4.2 nm/0.8 nm core/shell Ni/FePt reach 1.95 mA/cm² and 490 mA/mgPt at 0.9 Vmore »(vs. reversible hydrogen electrode, RHE), which are much higher than those of benchmark commercial Pt catalyst (0.34 mA/cm² and 92 mA/mgPt at 0.9 V). Our studies provide a robust approach to monodisperse core/shell NPs with non-precious metal core, making it possible to develop advanced NP catalysts with ultralow Pt content for ORR and many other heterogeneous reactions.« less

  1. Hybrid Composite Ni(OH)(2)@NiCo2O4 Grown on Carbon Fiber Paper for High-Performance Supercapacitors

    SciTech Connect (OSTI)

    Huang, L; Chen, DC; Ding, Y; Wang, ZL; Zeng, ZZ; Liu, ML

    2013-11-13

    We have successfully fabricated and tested the electrochemical performance of supercapacitor electrodes consisting of Ni(OH)(2) nanosheets coated on NiCo2O4 nanosheets grown on carbon fiber paper (CFP) current collectors. When the NiCo2O4 nanosheets are replaced by Co3O4 nanosheets, however, the energy and power density as well as the rate capability of the electrodes are significantly reduced, most likely due to the lower conductivity of Co3O4 than that of NiCo2O4. The 3D hybrid composite Ni(OH)(2)/ NiCo2O4/CFP electrodes demonstrate a high areal capacitance of 5.2 F/cm(2) at a cycling current density of 2 rnA/cm(2), with a capacitance retention of 79% as the cycling current density was increased from 2 to 50 mA/cm(2). The remarkable performance of these hybrid composite electrodes implies that supercapacitors based on them have potential for many practical applications.

  2. Method of plasma etching GA-based compound semiconductors

    DOE Patents [OSTI]

    Qiu, Weibin; Goddard, Lynford L.

    2013-01-01

    A method of plasma etching Ga-based compound semiconductors includes providing a process chamber and a source electrode adjacent thereto. The chamber contains a Ga-based compound semiconductor sample in contact with a platen which is electrically connected to a first power supply, and the source electrode is electrically connected to a second power supply. SiCl.sub.4 and Ar gases are flowed into the chamber. RF power is supplied to the platen at a first power level, and RF power is supplied to the source electrode. A plasma is generated. Then, RF power is supplied to the platen at a second power level lower than the first power level and no greater than about 30 W. Regions of a surface of the sample adjacent to one or more masked portions of the surface are etched at a rate of no more than about 25 nm/min to create a substantially smooth etched surface.

  3. Method of plasma etching Ga-based compound semiconductors

    DOE Patents [OSTI]

    Qiu, Weibin; Goddard, Lynford L.

    2012-12-25

    A method of plasma etching Ga-based compound semiconductors includes providing a process chamber and a source electrode adjacent to the process chamber. The process chamber contains a sample comprising a Ga-based compound semiconductor. The sample is in contact with a platen which is electrically connected to a first power supply, and the source electrode is electrically connected to a second power supply. The method includes flowing SiCl.sub.4 gas into the chamber, flowing Ar gas into the chamber, and flowing H.sub.2 gas into the chamber. RF power is supplied independently to the source electrode and the platen. A plasma is generated based on the gases in the process chamber, and regions of a surface of the sample adjacent to one or more masked portions of the surface are etched to create a substantially smooth etched surface including features having substantially vertical walls beneath the masked portions.

  4. AlGaAs-On-Insulator Nonlinear Photonics

    E-Print Network [OSTI]

    Pu, Minhao; Semenova, Elizaveta; Yvind, Kresten

    2015-01-01

    The combination of nonlinear and integrated photonics has recently seen a surge with Kerr frequency comb generation in micro-resonators as the most significant achievement. Efficient nonlinear photonic chips have myriad applications including high speed optical signal processing, on-chip multi-wavelength lasers, metrology, molecular spectroscopy, and quantum information science. Aluminium gallium arsenide (AlGaAs) exhibits very high material nonlinearity and low nonlinear loss when operated below half its bandgap energy. However, difficulties in device processing and low device effective nonlinearity made Kerr frequency comb generation elusive. Here, we demonstrate AlGaAs-on-insulator as a nonlinear platform at telecom wavelengths. Using newly developed fabrication processes, we show high-quality-factor (Q>100,000) micro-resonators with integrated bus waveguides in a planar circuit where optical parametric oscillation is achieved with a record low threshold power of 3 mW and a frequency comb spanning 350 nm i...

  5. Formation and properties of porous GaAs

    SciTech Connect (OSTI)

    Schmuki, P.; Lockwood, D.J.; Fraser, J.W.; Graham, M.J.; Isaacs, H.S.

    1996-06-01

    Porous structures on n-type GaAs (100) can be grown electrochemically in chloride-containing solutions. Crystallographic etching of the sample is a precursor stage of the attack. Polarization curves reveal the existanece of a critical onset potential for por formation (PFP). PFP is strongly dependent on the doping level of the sample and presence of surface defects. Good agreement between PFP and breakdown voltage of the space charge layer is found. Surface analysis by EDX, AES, and XPS show that the porous structure consists mainly of GaAs and that anion uptake in the structure can only observed after attackhas been initiated. Photoluminescence measurements reveal (under certain conditions) visible light emission from the porous structure.

  6. Resonant two-photon ionization spectroscopy of NiC Dale J. Brugh and Michael D. Morse

    E-Print Network [OSTI]

    Morse, Michael D.

    Resonant two-photon ionization spectroscopy of NiC Dale J. Brugh and Michael D. Morse University investigation of jet-cooled diatomic NiC has revealed a complex pattern of vibronic levels in the wave number as far to the blue as 26 951 cm 1 indicates that D0 NiC 3.34 eV, and the ionization energy of NiC has

  7. Influence of n-type versus p-type AlGaN electron-blocking layer on InGaN/GaN multiple quantum wells light-emitting diodes

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    to be further improved in order for the high- power LEDs to penetrate into the consumer market of gen- eral to higher optical output power and external quantum efficiency, compared to the devices with p-AlGaN EBLGaN/GaN based light-emitting diodes (LEDs) possess unique advantages including high energy conversion effi

  8. The transputer based GA. SP data acquisition system

    SciTech Connect (OSTI)

    Colombo, D.; Avano, B.; DePoli, M.; Maron, G. ); Negro, A.; Parlati, G. )

    1992-04-01

    In this paper, the new data acquisition for the GA.SP detector is presented. It is a distributed system based on a network of 40 T800 and T222 transputers linked to a VME system used for histogram storage. A 100 MBit/s FDDI ring connects the system to UNIX workstations used for the experiment control, histogram display and second level data analysis.

  9. Minority-carrier properties of GaAs on silicon

    SciTech Connect (OSTI)

    Ahrenkiel, R.K.; Al-Jassim, M.M.; Dunlavy, D.J.; Jones, K.M.; Vernon, S.M.; Tobin, S.P.; Haven, V.E.

    1988-07-18

    The minority-carrier lifetimes of the heteroepitaxial system of GaAs on Si are limited by recombination at mismatch dislocations. Here we show that increasing the thickness of the buffer layer, with an additional annealing step, reduces the dislocation density by about an order of magnitude. At the same time, the minority-carrier lifetime in these double heterostructures increases more than an order of magnitude.

  10. Ohmic contacts to p-type Ga

    E-Print Network [OSTI]

    Jorge Estevez, Humberto Angel

    1996-01-01

    resistivity was achieved by developing the Si(750A)/Pd(400A)/Zn(xA)/Pd(IOOA)/p-GaP scheme. Values of the contact resistivity in the range of 3xlO-5 to 7xlO-' nCM2 were obtained. It was found that the optimum Zn layer thickness is 30 A for the Pd and Si...

  11. Conductivity based on selective etch for GaN devices and applications thereof

    DOE Patents [OSTI]

    Zhang, Yu; Sun, Qian; Han, Jung

    2015-12-08

    This invention relates to methods of generating NP gallium nitride (GaN) across large areas (>1 cm.sup.2) with controlled pore diameters, pore density, and porosity. Also disclosed are methods of generating novel optoelectronic devices based on porous GaN. Additionally a layer transfer scheme to separate and create free-standing crystalline GaN thin layers is disclosed that enables a new device manufacturing paradigm involving substrate recycling. Other disclosed embodiments of this invention relate to fabrication of GaN based nanocrystals and the use of NP GaN electrodes for electrolysis, water splitting, or photosynthetic process applications.

  12. Continued development of metallization for GaAs concentrator cells

    SciTech Connect (OSTI)

    Tobin, S.P.

    1988-11-01

    The objective of this work was the integration of thermally stable metallizations with a high-efficiency GaAs concentrator cell process. For p-GaAs we used a Pt-TiN-Au metallization developed under a previous Sandia Contract. For n-GaAs the best results were obtained for AuGe-TiN-Au. Baseline p/n cells with a CrAu metallization achieved efficiencies of 25.4% at 200 suns. Efficiencies were about 22% at one sun. At one sun, p/n cells with high-temperature contacts were 22.2% efficient, showing that there is no efficiency penalty with the high-temperature metallization. Development efforts on n/p cells yielded high short-circuit currents and open-circuit voltages, with both conventional and high-temperature metallizations. Thermal annealing tests showed that cells with the Pt-TiN-Au metallization were more stable than those with the baseline metallization, withstanding a 15-minute anneal at 500/degree/C with negligible efficiency degradation. 22 refs., 64 figs., 54 tabs.

  13. InGaAsSb thermophotovoltaic diode physics evaluation

    SciTech Connect (OSTI)

    Charache, G.W.; Baldasaro, P.F.; Danielson, L.R. [Lockheed-Martin, Inc., Schenectady, NY (United States)] [and others

    1998-06-01

    The hotside operating temperatures for many projected thermophotovoltaic (TPV) conversion system applications are approximately 1,000 C, which sets an upper limit on the TPV diode bandgap of 0.6 eV from efficiency and power density considerations. This bandgap requirement has necessitated the development of new diode material systems, never previously considered for energy generation. To date, InGaAsSb quaternary diodes grown lattice-matched on GaSb substrates have achieved the highest performance. This report relates observed diode performance to electro-optic properties such as minority carrier lifetime, diffusion length and mobility and provides initial links to microstructural properties. This analysis has bounded potential diode performance improvements. For the 0.52 eV InGaAsSb diodes used in this analysis the measured dark current is 2 {times} 10{sup {minus}5} A/cm{sup 2}, versus a potential Auger limit 1 {times} 10{sup {minus}5} A/cm{sup 2}, a radiative limit of 2 {times} 10{sup {minus}6} A/cm{sup 2} (no photon recycling), and an absolute thermodynamic limit of 1.4 {times} 10{sup {minus}7} A/cm{sup 2}. These dark currents are equivalent to open circuit voltage gains of 20 mV (7%), 60 mV (20%) and 140 mV (45%), respectively.

  14. Ga lithography in sputtered niobium for superconductive micro and nanowires

    SciTech Connect (OSTI)

    Henry, M. David; Wolfley, Steve; Monson, Todd; Lewis, Rupert

    2014-08-18

    This work demonstrates the use of focused ion beam (FIB) implanted Ga as a lithographic mask for plasma etching of Nb films. Using a highly collimated Ga beam of a FIB, Nb is implanted 12?nm deep with a 14?nm thick Ga layer providing etch selectivity better than 15:1 with fluorine based etch chemistry. Implanted square test patterns, both 10??m by 10??m and 100??m by 100??m, demonstrate that doses above than 7.5?×?10{sup 15?}cm{sup ?2} at 30?kV provide adequate mask protection for a 205?nm thick, sputtered Nb film. The resolution of this dry lithographic technique is demonstrated by fabrication of nanowires 75?nm wide by 10??m long connected to 50??m wide contact pads. The residual resistance ratio of patterned Nb films was 3. The superconducting transition temperature (T{sub c})?=?7.7?K was measured using a magnetic properties measurement system. This nanoscale, dry lithographic technique was extended to sputtered TiN and Ta here and could be used on other fluorine etched superconductors such as NbN, NbSi, and NbTi.

  15. Influence of Mn and Ni on the microstructure and toughness of C-Mn-Ni weld metals

    SciTech Connect (OSTI)

    Zhang, Z.; Farrar, R.A. [Univ. of Southampton (United Kingdom). Dept. of Mechanical Engineering

    1997-05-01

    A systematic investigation has been carried out to study the microstructure and toughness of C-Mn-Ni low-alloy shielded metal arc (SMA) weld metals. The manganese and nickel concentrations were progressively changed to determine their influence on weld microstructure and mechanical properties as well as to identify their interactions. The results obtained showed that manganese and nickel have considerable effect on the weld metal microstructure, and both Mn and Ni affect the microstructure in a similar way, i.e., promoting acicular ferrite at the expense of proeutectoid ferrite (grain boundary ferrite and ferrite sideplates). The results in the top bead also showed that there is an optimum composition range that produces an optimum balance of weld metal microstructures. For optimum toughness, a combination of 0.6--1.4% manganese and 1.0--3.7% nickel is suggested. Additions beyond this limit promotes the formation of martensite and other microstructural features, which may be detrimental to weld metal toughness.

  16. The interfacial reaction of Ni on (100) Si?â??xGex (x=0, 0.25) and (111) Ge

    E-Print Network [OSTI]

    Jin, Lijuan

    The interfacial reaction of Ni with Si, Si?.??Ge?.??, and Ge at 400°C has been investigated. A uniform epitaxial NiSi film was obtained at 400°C for Ni-Silicidation on Si using rapid thermal annealing method. Similarly, ...

  17. Development of ZnNiCd coatings by pulse electrodeposition process Prabhu Ganesan, Swaminatha P. Kumaraguru, Branko N. Popov

    E-Print Network [OSTI]

    Popov, Branko N.

    Development of Zn­Ni­Cd coatings by pulse electrodeposition process Prabhu Ganesan, Swaminatha P indicated that Zn­Ni­Cd alloys exhibit superior barrier properties when compared to Cd or Zn­Ni coatings of corrosion resistant coating in aerospace, electrical, and fastener industries due to its excel- lent

  18. The corrosion behavior and hemocompatibility of TiNi alloys coated with DLC by plasma based ion implantation

    E-Print Network [OSTI]

    Zheng, Yufeng

    The corrosion behavior and hemocompatibility of TiNi alloys coated with DLC by plasma based ion successfully deposited on Ti­50.8 at.% Ni alloys using plasma based ion implantation (PBII) technique on the surface modification of TiNi alloys, including ion implan- tation, multi arc ion-plating as well as Ti

  19. Ni(III)/(IV) Bis(dicarbollide) as a Fast, Noncorrosive Redox Shuttle for Dye-Sensitized Solar Cells

    E-Print Network [OSTI]

    multiple redox transformations involving net charges of -2, -1, and 0, with Ni(II), Ni(III) (3), and Ni at the electrolyte interface. Previous DSC Fc/Fc+ couple work showed that dark currents can be suppressed by TiO2/Fc+ vs SCE (translating to a smaller potential difference between the dark electrode and quasi

  20. Chemically anchored NiOxcarbon composite fibers for Li-ion batteries with long cycle-life and

    E-Print Network [OSTI]

    Cao, Guozhong

    the research hot-pot of NiO based anodes for LIBs. Amorphous carbon, carbon nanotubes, graphene, and carbon enhanced properties.16,17 Carbon nanotubes were also used to prepare NiO­carbon composites via a surfaceO­gra- phene commonly began with nickel salts and graphene oxide, and the resultant NiO­graphene composites

  1. A numerical method for predicting the bending fatigue life of NiTi and stainless steel root canal

    E-Print Network [OSTI]

    Zheng, Yufeng

    A numerical method for predicting the bending fatigue life of NiTi and stainless steel root canal. A numerical method for predicting the bending fatigue life of NiTi and stainless steel root canal instruments­titanium alloy (NiTi) and stainless steel (SS) endodontic files using finite element analysis. Methodology

  2. Selective area growth and characterization of GaN nanocolumns, with and without an InGaN insertion, on semi-polar (11–22) GaN templates

    SciTech Connect (OSTI)

    Bengoechea-Encabo, A.; Albert, S.; Barbagini, F.; Sanchez-Garcia, M. A.; Calleja, E. [ISOM and Departamento de Ingenieria Electronica, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria s/n 28040 Madrid (Spain)] [ISOM and Departamento de Ingenieria Electronica, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria s/n 28040 Madrid (Spain); Zuñiga-Perez, J.; Mierry, P. de [CRHEA-CNRS, 06560 Valbonne (France)] [CRHEA-CNRS, 06560 Valbonne (France); Trampert, A. [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)] [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2013-12-09

    The aim of this work is the selective area growth (SAG) of GaN nanocolumns, with and without an InGaN insertion, by molecular beam epitaxyon semi-polar (11–22) GaN templates. The high density of stacking faults present in the template is strongly reduced after SAG. A dominant sharp photoluminescence emission at 3.473 eV points to high quality strain-free material. When embedding an InGaN insertion into the ordered GaN nanostructures, very homogeneous optical properties are observed, with two emissions originating from different regions of each nanostructure, most likely related to different In contents on different crystallographic planes.

  3. Structure and Magnetic Properties of Ce3(Ni/Al/Ga)11„A New Phase with the La3Al11 Structure Type

    Office of Scientific and Technical Information (OSTI)

    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 Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefieldSulfateSciTechtail. (Conference)Feedback System inStatus of theSciTechin aCrystals 2015, 5, 1-8;

  4. Gallium hole traps in irradiated KTiOPO{sub 4}:Ga crystals

    SciTech Connect (OSTI)

    Grachev, V.; Meyer, M.; Malovichko, G.; Hunt, A. W.

    2014-12-07

    Nominally pure and gallium doped single crystals of potassium titanyl phosphate (KTiOPO{sub 4}) have been studied by Electron Paramagnetic Resonance at low temperatures before and after irradiation. Irradiation with 20?MeV electrons performed at room temperature and liquid nitrogen temperature caused an appearance of electrons and holes. Gallium impurities act as hole traps in KTiOPO{sub 4} creating Ga{sup 4+} centers. Two different Ga{sup 4+} centers were observed, Ga1 and Ga2. The Ga1 centers are dominant in Ga-doped samples. For the Ga1 center, a superhyperfine structure with one nucleus with nuclear spin ½ was registered and attributed to the interaction of gallium electrons with a phosphorus nucleus or proton in its surrounding. In both Ga1 and Ga2 centers, Ga{sup 4+} ions substitute for Ti{sup 4+} ions, but with a preference to one of two electrically distinct crystallographic positions (site selective substitution). The Ga doping eliminates one of the shortcomings of KTP crystals—ionic conductivity of bulk crystals. However, this does not improve significantly the resistance of the crystals to electron and ?-radiation.

  5. Efficiency calculations of thin-film GaAs solar cells on Si substrates

    SciTech Connect (OSTI)

    Yamaguchi, M.; Amano, C.

    1985-11-01

    Dislocation effect upon the efficiency of single-crystal thin-film AlGaAs-GaAs heteroface solar cells on Si substrates is analyzed. Solar-cell properties are calculated based on a simple model; in the model, dislocations act as recombination centers to reduce the minority-carrier diffusion length in each layer and increase the space-charge layer recombination current. Numerical analysis is also carried out to optimize thin-film AlGaAs-GaAs heteroface solar-cell structures. The fabrication of thin-film AlGaAs-GaAs heteroface solar cells with a practical efficiency larger than 18% on Si substrates appears possible if the dislocation density in the thin-film GaAs layer is less than 10/sup 6/ cm/sup -2/.

  6. Compositionally graded relaxed AlGaN buffers on semipolar GaN for mid-ultraviolet emission

    SciTech Connect (OSTI)

    Young, Erin C.; Wu Feng; Haeger, Daniel A.; Nakamura, Shuji; Denbaars, Steven P.; Cohen, Daniel A.; Speck, James S.; Romanov, Alexey E.

    2012-10-01

    In this Letter, we report on the growth and properties of relaxed, compositionally graded Al{sub x}Ga{sub 1-x}N buffer layers on freestanding semipolar (2021) GaN substrates. Continuous and step compositional grades with Al concentrations up to x = 0.61 have been achieved, with emission wavelengths in the mid-ultraviolet region as low as 265 nm. Coherency stresses were relaxed progressively throughout the grades by misfit dislocation generation via primary (basal) slip and secondary (non-basal) slip systems. Threading dislocation densities in the final layers of the grades were less than 10{sup 6}/cm{sup 2} as confirmed by plan-view transmission electron microscopy and cathodoluminescence studies.

  7. Electron heating due to microwave photoexcitation in the high mobility GaAs/AlGaAs two dimensional electron system

    SciTech Connect (OSTI)

    Ramanayaka, A. N.; Mani, R. G.; Wegscheider, W.

    2013-12-04

    We extract the electron temperature in the microwave photo-excited high mobility GaAs/AlGaAs two dimensional electron system (2DES) by studying the influence of microwave radiation on the amplitude of Shubnikov-de Haas oscillations (SdHOs) in a regime where the cyclotron frequency, ?{sub c}, and the microwave angular frequency, ?, satisfy 2? ? ?{sub c} ? 3.5? The results indicate that increasing the incident microwave power has a weak effect on the amplitude of the SdHOs and therefore the electron temperature, in comparison to the influence of modest temperature changes on the dark-specimen SdH effect. The results indicate negligible electron heating under modest microwave photo-excitation, in good agreement with theoretical predictions.

  8. Origin of radiative recombination and manifestations of localization effects in GaAs/GaNAs core/shell nanowires

    SciTech Connect (OSTI)

    Chen, S. L.; Filippov, S.; Chen, W. M.; Buyanova, I. A.; Ishikawa, Fumitaro

    2014-12-22

    Radiative carrier recombination processes in GaAs/GaNAs core/shell nanowires grown by molecular beam epitaxy on a Si substrate are systematically investigated by employing micro-photoluminescence (?-PL) and ?-PL excitation (?-PLE) measurements complemented by time-resolved PL spectroscopy. At low temperatures, alloy disorder is found to cause localization of photo-excited carriers leading to predominance of optical transitions from localized excitons (LE). Some of the local fluctuations in N composition are suggested to lead to strongly localized three-dimensional confining potential equivalent to that for quantum dots, based on the observation of sharp and discrete PL lines within the LE contour. The localization effects are found to have minor influence on PL spectra at room temperature due to thermal activation of the localized excitons to extended states. Under these conditions, photo-excited carrier lifetime is found to be governed by non-radiative recombination via surface states which is somewhat suppressed upon N incorporation.

  9. Study of the one dimensional electron gas arrays confined by steps in vicinal GaN/AlGaN heterointerfaces

    SciTech Connect (OSTI)

    Li, Huijie E-mail: sh-yyang@semi.ac.cn; Zhao, Guijuan; Liu, Guipeng; Wei, Hongyuan; Jiao, Chunmei; Yang, Shaoyan E-mail: sh-yyang@semi.ac.cn; Wang, Lianshan; Zhu, Qinsheng

    2014-05-21

    One dimensional electron gas (1DEG) arrays in vicinal GaN/AlGaN heterostructures have been studied. The steps at the interface would lead to the lateral barriers and limit the electron movement perpendicular to such steps. Through a self-consistent Schrödinger-Poisson approach, the electron energy levels and wave functions were calculated. It was found that when the total electron density was increased, the lateral barriers were lowered due to the screening effects by the electrons, and the electron gas became more two-dimension like. The calculated 1DEG densities were compared to the experimental values and good agreements were found. Moreover, we found that a higher doping density is more beneficial to form 1-D like electron gas arrays.

  10. Terrestrial Concentrator PV Modules Based on GaInP/GaAs/Ge TJ Cells and Minilens Panels

    SciTech Connect (OSTI)

    Rumyantsev, V. D.; Sadchikov, N. A.; Chalov, A. E.; Ionova, E. A.; Friedman, D. J.; Glenn, G.

    2006-01-01

    This paper is a description of research activity in the field of cost-effective modules realizing the concept of very high solar concentration with small-aperture area Fresnel lenses and multijunction III-V cells. Structural simplicity and 'all-glass' design are the guiding principles of the corresponding development. The advanced concentrator modules are made with silicone Fresnel lens panels (from 8 up to 144 lenses, each lens is 4 times 4 cm{sup 2} in aperture area) with composite structure. GaInP/GaAs/Ge triple-junction cells with average efficiencies of 31.1 and 34.7% at 1000 suns were used for the modules. Conversion efficiency as high as 26.3% has been measured indoors in a test module using a newly developed large-area solar simulator.

  11. High Temperature Oxidation Behavior of gamma-Ni+gamma'-Ni3Al Alloys and Coatings Modified with Pt and Reactive Elements

    SciTech Connect (OSTI)

    Nan Mu

    2007-12-01

    Materials for high-pressure turbine blades must be able to operate in the high-temperature gases (above 1000 C) emerging from the combustion chamber. Accordingly, the development of nickel-based superalloys has been constantly motivated by the need to have improved engine efficiency, reliability and service lifetime under the harsh conditions imposed by the turbine environment. However, the melting point of nickel (1455 C) provides a natural ceiling for the temperature capability of nickel-based superalloys. Thus, surface-engineered turbine components with modified diffusion coatings and overlay coatings are used. Theses coatings are capable of forming a compact and adherent oxide scale, which greatly impedes the further transport of reactants between the high-temperature gases and the underlying metal and thus reducing attack by the atmosphere. Typically, these coatings contain {beta}-NiAl as a principal constituent phase in order to have sufficient aluminum content to form an Al{sub 2}O{sub 3} scale at elevated temperatures. The drawbacks to the currently-used {beta}-based coatings, such as phase instabilities, associated stresses induced by such phase instabilities, and extensive coating/substrate interdiffusion, are major motivations in this study to seek next-generation coatings. The high-temperature oxidation resistance of novel Pt + Hf-modified {gamma}-Ni + {gamma}-Ni{sub 3}Al-based alloys and coatings were investigated in this study. Both early-stage and 4-days isothermal oxidation behavior of single-phase {gamma}-Ni and {gamma}{prime}-Ni{sub 3}Al alloys were assessed by examining the weight changes, oxide-scale structures, and elemental concentration profiles through the scales and subsurface alloy regions. It was found that Pt promotes Al{sub 2}O{sub 3} formation by suppressing the NiO growth on both {gamma}-Ni and {gamma}{prime}Ni{sub 3}Al single-phase alloys. This effect increases with increasing Pt content. Moreover, Pt exhibits this effect even at lower temperatures ({approx}970 C) in the very early stage of oxidation. It was also inferred that Pt enhances the diffusive flux of aluminum from the substrate to the scale/alloy interface. Relatively low levels of hafnium addition to Pt-free {gamma}{prime}-Ni{sub 3}Al increased the extent of external NiO formation due to non-protective HfO{sub 2} formation. Accordingly, this effect intensified with increasing Hf content from 0.2 to 0.5 at.%.

  12. Advertising rates for 4NI, the Directory Portal for Northern IrelandAdd to the Guestbook of 4NI, the Directory Portal for Northern IreBack to 4NI, the Directory Portal for No 24 February 2004 @ 10:33:27 AM

    E-Print Network [OSTI]

    West, Stuart

    Advertising rates for 4NI, the Directory Portal for Northern IrelandAdd to the Guestbook of 4NI, the Directory Portal for Northern IreBack to 4NI, the Directory Portal for No 24 February 2004 @ 10:33:27 AM Directory Portal For Northern Ireland Industry News 20 February 2004 Some mammals can adjust sex

  13. A hole accelerator for InGaN/GaN light-emitting diodes Zi-Hui Zhang, Wei Liu, Swee Tiam Tan, Yun Ji, Liancheng Wang, Binbin Zhu, Yiping Zhang, Shunpeng Lu,

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    GaN/GaN light-emitting diodes (LEDs) has been significantly limited by the insufficient hole injection, the effectiveness of the hole ac- celerator is experimentally shown through achieving improved optical output power and reduced efficiency droop for the proposed InGaN/GaN LED. VC 2014 AIP Publishing LLC. [http://dx.doi.org/10

  14. InGaN/GaN light-emitting diode with a polarization tunnel junction Zi-Hui Zhang, Swee Tiam Tan, Zabu Kyaw, Yun Ji, Wei Liu et al.

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    to the enhanced optical output power and external quantum efficiency. Compared to the reference InGaN/GaN LEDs; accepted 29 April 2013; published online 15 May 2013) We report InGaN/GaN light-emitting diodes (LED have been devoted to boosting the optical output power and enhancing the external quantum efficiency

  15. 1EV GaN[subscript x]As[subscript 1-x-y]Sb[subscript y] material for lattice-matched III-V solar cell implementation on GaAs and Ge

    E-Print Network [OSTI]

    Yoon, Soon Fatt

    The effect of different arsenic species (As[subscript 2] or As[subscript 4]) on the quality of molecular beam epitaxy (MBE) grown GaNAsSb materials (samples A and B) and GaAs/ GaNAsSb/GaAs p+n-n+ devices (samples C and D) ...

  16. In situ carbonyl extraction of Ni from gaseous diffusion cells

    SciTech Connect (OSTI)

    Visnapuu, A. [USBM Salt Lake Research Center, Salt Lake City, UT (United States); Hollenberg, G.W. [Battelle Pacific Northwest Lab., Richland, WA (United States); Bundy, R.D. [Battelle Memorial Institute, Oak Ridge, TN (United States)

    1995-12-31

    This paper discusses the use of carbonyl processing technology for recovery of nickel from uranium isotope separation diffusion cells, and potential applications to recover nickel, iron, chromium, cobalt, and other carbonyl forming metals from nuclear waste while reducing the volume of the high level residue for more economic disposal. Nickel powder was carbonylated under static and dynamic conditions using only carbon monoxide to determine if the nickel powder would react rapidly enough to require no promoter. Nickel to Ni(CO){sub 4} conversion was realized in all cases and nickel metal was vapor deposited in the thermal decomposer, but the conversion rates in all cases the reaction were too slow for practical recovery. Addition of hydrogen sulfide gas as a promoter increased the conversion rate more than 500-fold over conversion with no promoter. Test summaries are provided in the paper; results indicate that promoter activated carbonylation is a viable approach for recovery of nickel from uranium isotope diffusion cells.

  17. Properties of Ni-Al under shock loading

    SciTech Connect (OSTI)

    Koskelo, A. C.; McClellan, K. J.; Brooks, J. D.; Paisley, Dennis L.; Swift, D. C.

    2002-01-01

    New models for the dynamic response of materials will be based increasingly on better understanding and representation of processes occurring at the microstructural level. These developments require advances in diagnostics and models which can be applied explicitly to microstructural response. Various phenomena occur at the microstructural level which are generally ignored or averaged out in continuum-level models. One example of such 'irregular hydrodynamics' is the roughness imparted to a shock wave as it propagates through a polycrystalline material. We have developed imaging techniques to study spatial variations in shock propagation through polycrystalline materials. In order to interpret spatially-resolved data from polycrystal samples, we need to compare with simulations which represent the microstructure. Here we describe work undertaken to develop a model of the dynamic response of individual grains. The material chosen was Ni-Al alloy, because it exhibits a relatively large degree of elastic anisotropy, and it is relatively easy to manufacture.

  18. Monopole resonance strengths in Ni-58 and Pb-208 

    E-Print Network [OSTI]

    Youngblood, David H.

    1997-01-01

    . Unfortunately, those data did not ex- tend to the small angles necessary to identify the GMR and to separate it from other multipoles. Both authors speculate of the E0 EWSR @7# are shown in Table I. Folded potentials and form factors were obtained using... and TABLE I. Parameters for folding model calculations. Nucleus c ~fm! a ~fm! ^r2& ~fm2! a02 Ex ~MeV! V ~MeV! W ~MeV! 58Ni 4.08 0.515 13.653 0.0194 17.0 35.5 21.5 208Pb 6.67 0.545 30.798 0.00297 13.7 40.5 26.0 both nuclei, with 160% of the E0...

  19. Thermomechanical behavior of 55Ni45Ti nitinol

    SciTech Connect (OSTI)

    Ford, D.S.; White, S.R. [Univ. of Illinois, Urbana, IL (United States)] [Univ. of Illinois, Urbana, IL (United States)

    1996-06-01

    Extensive and full range mechanical testing of 55Ni45Ti nitinol alloy wire up to failure over a wide range of testing temperatures is reported. Thermomechanical properties are obtained including: initial modulus, secondary modulus, critical martensitic start and finish stresses, plastic flow stress, recovery strain limit, failure stress and plastic modulus. The data is correlated with the Brinson constitutive model modified to account for full range loading. The ratio of austenite to martensite moduli was found to be 5.8 and the secondary modulus (stress-induced martensite) was found to be smaller by a factor of two when compared to the modulus of (stress-free) thermally induced martensite. The influence of the initial temperature treatment of the nitinol was shown to be pronounced within the transformation range. Reasonably accurate correlation is obtained with the modified Brinson constitutive model although there is some discrepancy in critical stress predictions which is partially attributed to experimental scatter.

  20. Undercooled and rapidly quenched Ni-Mo alloys

    SciTech Connect (OSTI)

    Tewari, S.N.; Glasgow, T.K.

    1986-01-01

    Hypoeutectic, eutectic, and hypereutectic nickel-molybdenum alloys were rapidly solidified by both bulk undercooling and melt spinning techniques. Alloys were undercooled in both electromagnetic levitation and differential thermal analysis equipment. The rate of recalescence depended upon the degree of initial undercooling and the nature (faceted or nonfaceted) of the primary nucleating phase. Alloy melts were observed to undercool more in the presence of primary Beta (NiMo intermetallic) phase than in gamma (fcc solid solution) phase. Melt spinning resulted in an extension of molybdenum solid solubility in gamma nickel, from 28 to 37.5 at % Mo. Although the microstructures observed by undercooling and melt spinning were similar the microsegregation pattern across the gamma dendries was different. The range of microstructures evolved was analyzed in terms of the nature of the primary phase to nucleate, its subsequent dendritic growth, coarsening and fragmentation, and final solidification of interfenderitic liquid.

  1. Graded InxGa1 xAs/GaAs 1.3 m wavelength light emitting diode structures grown with molecular beam epitaxy

    E-Print Network [OSTI]

    Graded InxGa1 xAs/GaAs 1.3 m wavelength light emitting diode structures grown with molecular beam 11 June 1997; accepted for publication 29 September 1997 In this study 1.1­1.3 m wavelength light at a lower cost. Such a technology could have an impact on the economic feasibility of fiber to the home

  2. Si3N4 on GaAs by direct electron cyclotron resonance plasma assisted nitridation of Si layer in Si/GaAs structure

    E-Print Network [OSTI]

    Rockett, Angus

    from XPS as a function of photoelectron takeoff angle, initially increased rapidly with nitridation either from the higher temperature or from nitridation of all of the Si, leaving the Si3N4 in direct contact with the GaAs. © 1998 American Vacuum Society. S0734-211X 98 00302-3 I. INTRODUCTION Ga

  3. CH{sub 4}-CO{sub 2} reforming over Ni-substituted barium hexaaluminate catalysts

    SciTech Connect (OSTI)

    Gardner, Todd H. [U.S. DOE; Spivey, James J. [ORISE; Kugler, Edwin L.; Pakhare, Devendra

    2013-03-30

    A series of Ni-substituted barium hexaaluminate catalysts, Ba{sub 0.75}Ni{sub y}Al{sub 12?y}O{sub 19??} (y = 0.4, 0.6 and 1.0), were tested for CO{sub 2} reforming of CH{sub 4} at temperatures between 200 and 900 °C. Temperature programmed surface reaction results show that the reaction lights-off in a temperature range between 448 and 503 °C with a consistent decrease in light-off temperature with increasing Ni substitution. Isothermal runs performed at 900 °C show near equilibrium conversion and stable product concentrations for 18 h on all catalysts. Temperature programmed oxidation of the used catalysts show that the amount of carbon deposited on the catalyst increases with Ni substitution. High resolution XRD of the used Ba{sub 0.75}Ni{sub 0.4}Al{sub 11.6}O{sub 19??} catalyst shows a statistically significant contraction of the unit cell which is the result of NiO reduction from the lattice. XRD of the used catalyst also confirms the presence of graphitic carbon. XPS and ICP measurements of the as prepared catalysts show that lower levels of Ni substitution result in an increasing proportion of Ba at the surface.

  4. Structural and Electrical Functionality of NiO Interfacial Films in Bulk Heterojunction Organic Solar Cells

    SciTech Connect (OSTI)

    Irwin, M.D.; Servaites, J.D.; Buchholz, B.D.; Leever, B.J.; Liu, J.; Emery, J.D.; Zhang, M.; Song, J.H.; Durstock, M.F.; Freeman, Arthur J.; Bedzyk, M.J.; Hersam, Mark C.; Chang, R.P.H.; Ratner, Mark A.; Marks, Tobin J.

    2011-01-01

    The functionality of NiO interfacial layers in enhancing bulk heterojunction (BHJ) organic photovoltaic (OPV) cell performance is investigated by integrated characterization of the electrical properties, microstructure, electronic structure, and optical properties of thin NiO films grown on glass/ITO electrodes. These NiO layers are found to be advantageous in BHJ OPV applications due to favorable energy band levels, interface passivation, p-type character, crystallinity, smooth surfaces, and optical transparency. The NiO overlayers are fabricated via pulsed-laser deposition and found to have a work function of ?5.3 eV. They are investigated by both topographic and conductive atomic force microscopy and shown to passivate interfacial charge traps. The films also have an average optical transparency of >80% in the visible range, crucial for efficient OPV function, and have a near-stoichiometric Ni:O surface composition. By grazing-incidence X-ray diffraction, the NiO thin films are shown to grow preferentially in the (111) direction and to have the fcc NaCl crystal structure. Diodes of p?n structure and first-principles electronic structure calculations indicate that the NiO interlayer is preferentially conductive to holes, with a lower hole charge carrier effective mass versus that of electrons. Finally, the implications of these attributes in advancing efficiencies for state-of-the-art OPV systems—in particular, improving the open circuit voltage (V{sub OC})—are discussed.

  5. On characterisation of wire-arc-plasma-sprayed Ni on alumina substrate

    SciTech Connect (OSTI)

    Laik, A.; Chakravarthy, D.P.; Kale, G.B. . E-mail: gbkale@apsara.barc.ernet.in

    2005-08-15

    A study was carried out on metal-ceramic bonding produced by the technique of wire-arc-plasma spraying of Ni on Al{sub 2}O{sub 3} substrate. The Ni layer and the Ni/Al{sub 2}O{sub 3} interface were characterised using optical and electro-optic techniques. The plasma-deposited Ni layer shows a uniform lamellar microstructure throughout the cross-section. The metal-ceramic interface was found to be well bonded with no pores, flaws or cracks in the as-sprayed condition. The optical metallography and concentration profiles established with the help of an electron probe microanalyser confirmed the absence of any intermediate phase at the interface. An annealing treatment at 1273 K for 24 h on the plasma-coated samples did not result in formation of any intermetallic compound or spinel at the Ni/Al{sub 2}O{sub 3} interface. This indicates that the oxygen picked up by Ni during the spraying operation is less than the threshold value required to form the spinel NiAl{sub 2}O{sub 4}.

  6. (001) Oriented piezoelectric films prepared by chemical solution deposition on Ni foils

    SciTech Connect (OSTI)

    Yeo, Hong Goo, E-mail: hxy162@psu.edu; Trolier-McKinstry, Susan [Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2014-07-07

    Flexible metal foil substrates are useful in some microelectromechanical systems applications including wearable piezoelectric sensors or energy harvesters based on Pb(Zr,Ti)O? (PZT) thin films. Full utilization of the potential of piezoelectrics on metal foils requires control of the film crystallographic texture. In this study, (001) oriented PZT thin films were grown by chemical solution deposition (CSD) on Ni foil and Si substrates. Ni foils were passivated using HfO? grown by atomic layer deposition in order to suppress substrate oxidation during subsequent thermal treatment. To obtain the desired orientation of PZT film, strongly (100) oriented LaNiO? films were integrated by CSD on the HfO? coated substrates. A high level of (001) LaNiO? and PZT film orientation were confirmed by X-ray diffraction patterns. Before poling, the low field dielectric permittivity and loss tangents of (001) oriented PZT films on Ni are near 780 and 0.04 at 1 kHz; the permittivity drops significantly on poling due to in-plane to out-of-plane domain switching. (001) oriented PZT film on Ni displayed a well-saturated hysteresis loop with a large remanent polarization ~36 ?C/cm², while (100) oriented PZT on Si showed slanted P-E hysteresis loops with much lower remanent polarizations. The |e{sub 31,f}| piezoelectric coefficient was around 10.6 C/m² for hot-poled (001) oriented PZT film on Ni.

  7. Carbon-Supported IrNi Core-Shell Nanoparticles: Synthesis Characterization and Catalytic Activity

    SciTech Connect (OSTI)

    K Sasaki; K Kuttiyiel; L Barrio; D Su; A Frenkel; N Marinkovic; D Mahajan; R Adzic

    2011-12-31

    We synthesized carbon-supported IrNi core-shell nanoparticles by chemical reduction and subsequent thermal annealing in H{sub 2}, and verified the formation of Ir shells on IrNi solid solution alloy cores by various experimental methods. The EXAFS analysis is consistent with the model wherein the IrNi nanoparticles are composed of two-layer Ir shells and IrNi alloy cores. In situ XAS revealed that the Ir shells completely protect Ni atoms in the cores from oxidation or dissolution in an acid electrolyte under elevated potentials. The formation of Ir shell during annealing due to thermal segregation is monitored by time-resolved synchrotron XRD measurements, coupled with Rietveld refinement analyses. The H{sub 2} oxidation activity of the IrNi nanoparticles was found to be higher than that of a commercial Pt/C catalyst. This is predominantly due to Ni-core-induced Ir shell contraction that makes the surface less reactive for IrOH formation, and the resulting more metallic Ir surface becomes more active for H{sub 2} oxidation. This new class of core-shell nanoparticles appears promising for application as hydrogen anode fuel cell electrocatalysts.

  8. The polygallides: Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2}

    SciTech Connect (OSTI)

    Peter, Sebastian C. [Department of Chemistry, Northwestern University, 2145N. Sheridan Road, Evanston, IL 60208 (United States); New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064 (India); Malliakas, Christos D. [Department of Chemistry, Northwestern University, 2145N. Sheridan Road, Evanston, IL 60208 (United States); Nakotte, Heinze; Kothapilli, Karunakar [Physics Department, New Mexico State University, Las Cruces, NM 88003 (United States); Los Alamos Neutron Science Center, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Rayaprol, Sudhindra [UGC-DAE Consortium for Scientific Research, Mumbai Centre, BARC, R-5 Shed, Trombay, Mumbai 400085 (India); Schultz, Arthur J. [X-Ray Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Kanatzidis, Mercouri G., E-mail: m-kanatzidis@northwestern.edu [Department of Chemistry, Northwestern University, 2145N. Sheridan Road, Evanston, IL 60208 (United States); Materials Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States)

    2012-03-15

    Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} were obtained from reactions of Yb and Ge in excess liquid gallium. The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} was refined using X-ray and neutron diffraction data on selected single crystals. Yb{sub 3}Ga{sub 7}Ge{sub 3} crystallizes in the monoclinic space group C2/c with lattice constants a=12.2261(20) Angstrom-Sign , b=10.7447(20) Angstrom-Sign , c=8.4754(17) Angstrom-Sign and {beta}=110.288(30) Degree-Sign (neutron diffraction data). The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} is an intergrowth of planar layers of YbGa{sub x}Ge{sub y} and puckered layers of (Ge){sub n}. YbGa{sub 4}Ge{sub 2} crystallizes in a modified PuGa{sub 6} structure type in the tetragonal polar space group I4cm with lattice constants a=b=5.9874(6) Angstrom-Sign and c=15.1178(19) Angstrom-Sign . The structure of YbGa{sub 4}Ge{sub 2} is an intergrowth of puckered Ga layers and puckered Ga{sub x}Ge{sub y} layers with Yb atoms residing within the channels formed by the connection of the two layers. Physical properties, resistivity ({rho}), magnetic susceptibility ({chi}) and specific heat (C) were measured for Yb{sub 3}Ga{sub 7}Ge{sub 3}. No magnetic ordering was observed. It was found that at low temperatures, {rho} varied as T{sup 2} and C{proportional_to}T, indicating Fermi-liquid regime in Yb{sub 3}Ga{sub 7}Ge{sub 3} at low temperatures. - Graphical abstract: The compounds Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} are obtained from reactions of Yb and Ge in excess liquid gallium. Highlights: Black-Right-Pointing-Pointer Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} are two new polygallides. Black-Right-Pointing-Pointer The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} was established using neutron diffraction data. Black-Right-Pointing-Pointer YbGa{sub 4}Ge{sub 2} is one of the rare polar intermetallic compounds. Black-Right-Pointing-Pointer The physical properties of Yb{sub 3}Ga{sub 7}Ge{sub 3} point to a Fermi-liquid regime at low temperature.

  9. Temporally and spatially resolved photoluminescence investigation of (112{sup ¯}2) semi-polar InGaN/GaN multiple quantum wells grown on nanorod templates

    SciTech Connect (OSTI)

    Liu, B.; Smith, R.; Athanasiou, M.; Yu, X.; Bai, J.; Wang, T.

    2014-12-29

    By means of time-resolved photoluminescence (PL) and confocal PL measurements, temporally and spatially resolved optical properties have been investigated on a number of In{sub x}Ga{sub 1?x}N/GaN multiple-quantum-well (MQW) structures with a wide range of indium content alloys from 13% to 35% on (112{sup ¯}2) semi-polar GaN with high crystal quality, obtained through overgrowth on nanorod templates. With increasing indium content, the radiative recombination lifetime initially increases as expected, but decreases if the indium content further increases to 35%, corresponding to emission in the green spectral region. The reduced radiative recombination lifetime leads to enhanced optical performance for the high indium content MQWs as a result of strong exciton localization, which is different from the behaviour of c-plane InGaN/GaN MQWs, where quantum confined Stark effect plays a dominating role in emission process.

  10. Fabrication of hollow mesoporous NiO hexagonal microspheres via hydrothermal process in ionic liquid

    SciTech Connect (OSTI)

    Zhao, Jinbo; School of Materials Science and Engineering, Shandong University, 250061, Jinan ; Wu, Lili; School of Materials Science and Engineering, Shandong University, 250061, Jinan ; Zou, Ke; School of Materials Science and Engineering, Shandong University, 250061, Jinan

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer Ni(OH){sub 2} precursors were synthesized in ionic liquid and water solution by hydrothermal method. Black-Right-Pointing-Pointer NiO hollow microspheres were prepared by thermal treatment of Ni(OH){sub 2} precursors. Black-Right-Pointing-Pointer NiO hollow microspheres were self-assembled by mesoporous cubic and hexagonal nanocrystals with high specific surface area. Black-Right-Pointing-Pointer The mesoporous structure is stable at 773 K. Black-Right-Pointing-Pointer The ionic liquid absorbed on the O-terminate surface of the crystals to form hydrogen bond and played key roles in determining the final shape of the NiO novel microstructure. -- Abstract: The novel NiO hexagonal hollow microspheres have been successfully prepared by annealing Ni(OH){sub 2}, which was synthesized via an ionic liquid-assisted hydrothermal method. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), N{sub 2} adsorption-desorption and Fourier transform infrared spectrometer (FTIR). The results show that the hollow NiO microstructures are self-organized by mesoporous cubic and hexagonal nanocrystals. The mesoporous structure possessed good thermal stability and high specific surface area (ca. 83 m{sup 2}/g). The ionic liquid 1-butyl-3methylimidazolium tetrafluoroborate ([Bmim][BF{sub 4}]) was found to play a key role in controlling the morphology of NiO microstructures during the hydrothermal process. The special hollow mesoporous architectures will have potential applications in many fields, such as catalysts, absorbents, sensors, drug-delivery carriers, acoustic insulators and supercapacitors.

  11. H irradiation effects on the GaAs-like Raman modes in GaAs{sub 1-x}N{sub x}/GaAs{sub 1-x}N{sub x}:H planar heterostructures

    SciTech Connect (OSTI)

    Giulotto, E. Geddo, M.; Patrini, M.; Guizzetti, G.; Felici, M.; Capizzi, M.; Polimeni, A.; Martelli, F.; Rubini, S.

    2014-12-28

    The GaAs-like longitudinal optical phonon frequency in two hydrogenated GaAs{sub 1-x}N{sub x}/GaAs{sub 1-x}N{sub x}:H microwire heterostructures—with similar N concentration, but different H dose and implantation conditions—has been investigated by micro-Raman mapping. In the case of GaAs{sub 0.991}N{sub 0.009} wires embedded in barriers where GaAs-like properties are recovered through H irradiation, the phonon frequency in the barriers undergoes a blue shift with respect to the wires. In GaAs{sub 0.992}N{sub 0.008} wires embedded in less hydrogenated barriers, the phonon frequency exhibits an opposite behavior (red shift). Strain, disorder, phonon localization effects induced by H-irradiation on the GaAs-like phonon frequency are discussed and related to different types of N-H complexes formed in the hydrogenated barriers. It is shown that the red (blue) character of the frequency shift is related to the dominant N-2H (N-3H) type of complexes. Moreover, for specific experimental conditions, an all-optical determination of the uniaxial strain field is obtained. This may improve the design of recently presented devices that exploit the correlation between uniaxial stress and the degree of polarization of photoluminescence.

  12. Features of a priori heavy doping of the n-TiNiSn intermetallic semiconductor

    SciTech Connect (OSTI)

    Romaka, V. A.; Rogl, P.; Romaka, V. V.; Hlil, E. K.; Stadnyk, Yu. V.; Budgerak, S. M.

    2011-07-15

    The crystal structure, the distribution of electron density, and the energy, kinetic, and magnetic properties of the n-TiNiSn intermetallic semiconductor are investigated. It is shown that a priori doping of n-TiNiSn with donors originates from partial, up to 0.5 at %, redistribution of Ti and Ni atoms in crystallographic sites of Ti atoms. The correlation is established between the donor concentration, amplitude of modulation of the continuous energy bands, and degree of filling of low-scale fluctuation potential wells with charge carriers. The results obtained are discussed within the Shklovskii-Efros model of a heavily doped and compensated semiconductor.

  13. In Situ Observations of the Atomistic Mechanisms of Ni Catalyzed Low Temperature Graphene Growth

    E-Print Network [OSTI]

    Patera, Laerte L.; Africh, Cristina; Weatherup, Robert S.; Blume, Raoul; Bhardwaj, Sunil; Castellarin-Cudia, Carla; Knop-Gericke, Axel; Schloegl, Robert; Comelli, Giovanni; Hofmann, Stephan; Cepek, Cinzia

    2013-08-08

    , CA (283.2eV), CDis (283.8eV), CGr (284.4eV), and CB (284.8eV). The C1s spectrum of the graphene covered Ni(111) surface in Figure 3c shows a dominant CB component, ?72% of the total C1s intensity, with the CDis and CGr contributing ?12% and ?15... -range ordered structure, would show a component of similar binding energy resulting from a similar charge transfer from Ni to embedded C atoms. This broader assignment of CA could account for previous observations of a CA peak under conditions where Ni2C may...

  14. Improved synthesis and crystal structure of the flexible pillared layer porous coordination polymer: Ni(1,2-bis(4-pyridyl)ethylene)[Ni(CN)(4)

    SciTech Connect (OSTI)

    Wong-Ng, W.; Culp, J. T.; Chen, Y. S.; Zavalij, P.; Espinal, L.; Siderius, D. W.; Allen, A. J.; Scheins, S Matranga, C

    2013-04-04

    This paper reports our synthesis of flexible coordination polymer, Ni(L)[Ni(CN){sub 4}], (L = 1,2-bis(4- pyridyl)ethylene (nicknamed bpene)), and its structural characterization using synchrotron single crystal X-ray diffraction. The structure of the purplish crystals has been determined to be monoclinic, space group P2{sub 1}/m, a = 13.5941(12) Å, b = 14.3621(12) Å, c = 14.2561(12) Å, {beta} = 96.141(2){degrees|, V = 2767.4(4) Å{sup 3}, Z = 4, D{sub c} = 1.46 g cm{sup -1}. Ni(bpene)[Ni(CN){sub 4}] assumes a pillared layer structure with layers defined by Ni[Ni(CN){sub 4}]{sub n} nets and bpene ligands acting as pillars. With the present crystallization technique which involves the use of concentrated ammonium hydroxide solution and dimethyl sulfoxide (DMSO), disordered free bpene ligands and solvents of crystallization (DMSO and water molecules) occupy the pores, resulting in a formula of Ni(bpene)[Ni(CN){sub 4}](1/2)bpene.DMSO.2H{sub 2}O, or Ni{sub 2}N{sub 7}C{sub 24}H{sub 2}.5SO{sub 3}. Without the inclusion of free bpene ligands and solvent molecules, the free volume is approximately 61% of the total volume; this free volume fraction is reduced to 50% with the free ligands present. Pores without the free ligands were found to have a local diameter of 5.7 Å and a main aperture of 3.5 Å. Based on the successful crystal synthesis, we also devised a new bulk synthetic technique which yielded a polycrystalline material with a significantly improved CO{sub 2} uptake as compared to the originally reported powder material. The improved synthetic technique yielded a polycrystalline material with 40% higher CO{sub 2} uptake compared to the previously reported powder material. An estimated 14.4 molecules of CO{sub 2} per unit cell was obtained.

  15. A semisynthetic strategy leads to alteration of the backbone amidate ligand in the NiSOD active site

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

    Campeciño, Julius O.; Dudycz, Lech W.; Tumelty, David; Berg, Volker; Cabelli, Diane E.; Maroney, Michael J.

    2015-07-01

    Computational investigations have implicated the amidate ligand in nickel superoxide dismutase (NiSOD) in stabilizing Ni-centered redox catalysis and in preventing cysteine thiolate ligand oxidation. To test these predictions, we have used an experimental approach utilizing a semisynthetic scheme that employs native chemical ligation of a pentapeptide (HCDLP) to recombinant S. coelicolor NiSOD lacking these N-terminal residues, N?5-NiSOD. Wild-type enzyme produced in this manner exhibits the characteristic spectral properties of recombinant WT-NiSOD and is as catalytically active. The semisynthetic scheme was also employed to construct a variant where the amidate ligand was converted to a secondary amine, H1*-NiSOD, a novel strategymore »that retains a backbone N-donor atom. The H1*-NiSOD variant was found to have only ~1% of the catalytic activity of the recombinant wild-type enzyme, and had altered spectroscopic properties. X-ray absorption spectroscopy reveals a four-coordinate planar site with N2S2-donor ligands, consistent with electronic absorption spectroscopic results indicating that the Ni center in H1*-NiSOD is mostly reduced in the as-isolated sample, as opposed to 50:50 Ni(II)/Ni(III) mixture that is typical for the recombinant wild-type enzyme. The EPR spectrum of as-isolated H1*-NiSOD accounts for ~11% of the Ni in the sample and is similar to WT-NiSOD, but more axial, with gz x,y. 14N-hyperfine is observed on gz« less

  16. Low dimensional GaAs/air vertical microcavity lasers

    SciTech Connect (OSTI)

    Gessler, J.; Steinl, T.; Fischer, J.; Höfling, S.; Schneider, C.; Kamp, M.; Mika, A.; S?k, G.; Misiewicz, J.

    2014-02-24

    We report on the fabrication of gallium arsenide (GaAs)/air distributed Bragg reflector microresonators with indium gallium arsenide quantum wells. The structures are studied via momentum resolved photoluminescence spectroscopy which allows us to investigate a pronounced optical mode quantization of the photonic dispersion. We can extract a length parameter from these quantized states whose upper limit can be connected to the lateral physical extension of the microcavity via analytical calculations. Laser emission from our microcavity under optical pumping is observed in power dependent investigations.

  17. Distribution of bismuth atoms in epitaxial GaAsBi

    SciTech Connect (OSTI)

    Sales, David [Universidad de Cadiz, Spain; Guerreo, E. [Universidad de Cadiz, Spain; Rodrigo, J.F. [Universidad de Cadiz, Spain; Galindo, P.L. [Universidad de Cadiz, Spain; Yanez, A. [University of Cadiz, Spain; Shafi, M. [University of Nottingham, Nottingham UK; Khatab, A. [University of Nottingham, Nottingham UK; Mari, R.H. [University of Nottingham, Nottingham UK; Henini, M. [University of Nottingham, Nottingham UK; Novikov, S. [University of Nottingham, Nottingham UK; Chisholm, Matthew F [ORNL; Molina, S.I. [Universidad de Cadiz, Spain

    2011-01-01

    The distribution of Bi atoms in epitaxial GaAs{sub (1-x)}Bi{sub x} is analyzed through aberration-corrected Z-contrast images. The relation between the atomic number and the intensity of the images allows quantifying the distribution of Bi atoms in this material. A bidimensional map of Bi atoms is extracted showing areas where nanoclustering is possible and evidencing the location of Bi at As-substitutional positions in the lattice. The distribution of Bi atoms differs from a random spatial pattern of Bi atoms in the material.

  18. Enhanced Magnetism of Fe3O4 Nanoparticles with Ga Doping

    SciTech Connect (OSTI)

    Pool, V. L.; Klem, M. T.; Chorney, C. L.; Arenholz, E.; Idzerda, Y.U.

    2010-10-22

    Magnetic (Ga{sub x}Fe{sub 1-x}){sub 3}O{sub 4} nanoparticles with 5%-33% gallium doping (x = 0.05-0.33) were measured using x-ray absorption spectroscopy and x-ray magnetic circular dichroism to determine that the Ga dopant is substituting for Fe{sub 3+} as Ga{sub 3+} in the tetrahedral A-site of the spinel structure, resulting in an overall increase in the total moment of the material. Frequency-dependent alternating-current magnetic susceptibility measurements showed these particles to be weakly interacting with a reduction of the cubic anisotropy energy term with Ga concentration. The element-specific dichroism spectra show that the average Fe moment is observed to increase with Ga concentration, a result consistent with the replacement of A-site Fe by Ga.

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

    SciTech Connect (OSTI)

    Vernon, S.M. )

    1993-04-01

    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. Shape memory and superelasticity in polycrystalline Cu-Al-Ni microwires

    E-Print Network [OSTI]

    Chen, Ying

    We report a strategy to significantly improve the ductility and achieve large superelastic and shape memory strains in polycrystalline Cu–Al–Ni shape memory alloys that are normally brittle. We use a liquid-phase (Taylor) ...

  1. Contact-induced spin polarization of monolayer hexagonal boron nitride on Ni(111)

    SciTech Connect (OSTI)

    Ohtomo, Manabu; Entani, Shiro; Matsumoto, Yoshihiro; Naramoto, Hiroshi; Sakai, Seiji; Yamauchi, Yasushi; Kuzubov, Alex A.; Eliseeva, Natalya S.; Avramov, Pavel V.

    2014-02-03

    Hexagonal boron nitride (h-BN) is a promising barrier material for graphene spintronics. In this Letter, spin-polarized metastable de-excitation spectroscopy (SPMDS) is employed to study the spin-dependent electronic structure of monolayer h-BN/Ni(111). The extreme surface sensitivity of SPMDS enables us to elucidate a partial filling of the in-gap states of h-BN without any superposition of Ni 3d signals. The in-gap states are shown to have a considerable spin polarization parallel to the majority spin of Ni. The positive spin polarization is attributed to the ?-d hybridization and the effective spin transfer to the nitrogen atoms at the h-BN/Ni(111) interface.

  2. Thermodynamic modeling and experimental validation of the Fe-Al-Ni-Cr-Mo alloy system

    SciTech Connect (OSTI)

    Teng, Zhenke; Zhang, F; Miller, Michael K; Liu, Chain T; Huang, Shenyan; Chou, Y.T.; Tien, R; Chang, Y A; Liaw, Peter K

    2012-01-01

    NiAl-type precipitate-strengthened ferritic steels have been known as potential materials for the steam turbine applications. In this study, thermodynamic descriptions of the B2-NiAl type nano-scaled precipitates and body-centered-cubic (BCC) Fe matrix phase for four alloys based on the Fe-Al-Ni-Cr-Mo system were developed as a function of the alloy composition at the aging temperature. The calculated phase structure, composition, and volume fraction were validated by the experimental investigations using synchrotron X-ray diffraction and atom probe tomography. With the ability to accurately predict the key microstructural features related to the mechanical properties in a given alloy system, the established thermodynamic model in the current study may significantly accelerate the alloy design process of the NiAl-strengthened ferritic steels.

  3. Hydroxyl and molecular H2O diffusivity in a haploandesitic melt Huaiwei Ni a,b,

    E-Print Network [OSTI]

    Zhang, Youxue

    Hydroxyl and molecular H2O diffusivity in a haploandesitic melt Huaiwei Ni a,b, , Zhengjiu Xu c) rather than hydroxyl group (OH), water diffusivity has been experimentally determined for a variety

  4. Thermal properties of Ni-substituted LaCoO{sub 3} perovskite

    SciTech Connect (OSTI)

    Thakur, Rasna Thakur, Rajesh K. Gaur, N. K.; Srivastava, Archana

    2014-04-24

    With the objective of exploring the unknown thermodynamic behavior of LaCo{sub 1?x}Ni{sub x}O{sub 3} family, we present here an investigation of the temperature-dependent (10K ? T ? 300K) thermodynamic properties of LaCo{sub 1?x}Ni{sub x}O{sub 3} (x=0.1, 0.3, 0.5). The specific heat of LaCoO3 with Ni doping in the perovskite structure at B-site has been studied by means of a Modified Rigid Ion Model (MRIM). This replacement introduces large cation variance at B-site hence the specific heat increases appreciably. We report here probably for the first time the cohesive energy, Reststrahlen frequency (?) and Debye temperature (?{sub D}) of LaCo{sub 1?x}Ni{sub x}O{sub 3} compounds.

  5. Measuring relative performance of an EDS detector using a NiO...

    Office of Scientific and Technical Information (OSTI)

    performance of energy dispersive spectrometers (EDS) on a TEM is discussed. A NiO thin-film standard fabricated at Sandia CA is used. A performance parameter,, is measured and...

  6. Scattering of xenon from Ni,,111...: Collision-induced corrugation and energy transfer dynamics

    E-Print Network [OSTI]

    , Stanford, California 94305 Received 19 April 1999; accepted 26 October 1999 Experiments have been conducted in which a beam of xenon atoms collides with a clean Ni 111 surface, and the speed and angular super- sonic molecular

  7. Fabrication and characterization of porous NiTi Shape Memory Alloy by elevated pressure sintering 

    E-Print Network [OSTI]

    Vandygriff, Eric Layton

    2002-01-01

    have not been adequately developed. Currently, three methods are commonly used for producing porous NiTi SMAs from elemental powders. These methods include conventional sintering, Self-propagating High-temperature Synthesis (SHS), and sintering...

  8. Study on Degradation of Solid Oxide Fuel Cell With Pure Ni Anode Zhenjun Jiaoa

    E-Print Network [OSTI]

    Kasagi, Nobuhide

    Study on Degradation of Solid Oxide Fuel Cell With Pure Ni Anode Zhenjun Jiaoa , Naoki Shikazonoa Solid oxide fuel cell (SOFC) has attracted more and more attentions in the last few decades

  9. Isoscalar and neutron modes in the E 1 spectra of Ni isotopes...

    Office of Scientific and Technical Information (OSTI)

    Isoscalar and neutron modes in the E 1 spectra of Ni isotopes and the relevance of shell effects and the continuum Citation Details In-Document Search This content will become...

  10. Pressure-Induced Structural Phase Transition in CeNi: X-ray and...

    Office of Scientific and Technical Information (OSTI)

    Pressure-Induced Structural Phase Transition in CeNi: X-ray and Neutron Scattering Studies and First-Principles Calculations Citation Details In-Document Search This content will...

  11. Shape-Memory Transformations of NiTi: Minimum-Energy Pathways...

    Office of Scientific and Technical Information (OSTI)

    Details In-Document Search This content will become publicly available on December 24, 2015 Title: Shape-Memory Transformations of NiTi: Minimum-Energy Pathways between Austenite,...

  12. Low Spring Index NiTi Coil Actuators for Use in Active Compression Garments

    E-Print Network [OSTI]

    Holschuh, Bradley T.

    This paper describes the modeling, development, and testing of low spring index nickel titanium (NiTi) coil actuators designed for use in wearable compression garments, and presents a prototype tourniquet system using these ...

  13. Graphene-on-Insulator Transistors Made Using C on Ni Chemical-Vapor Deposition

    E-Print Network [OSTI]

    Keast, Craig L.

    Graphene transistors are made by transferring a thin graphene film grown on Ni onto an insulating SiO[subscript 2] substrate. The properties and integration of these graphene-on-insulator transistors are presented and ...

  14. The thermomechanical constitutive experimentation of NiTi shape memory alloy strips and rods 

    E-Print Network [OSTI]

    Howard, Stephen David

    1995-01-01

    The purpose of this thesis was to study the effect of temperature on the thermomechanical constitutive behavior of NiTi shape memory alloy strip and rod specimens. The stress-strain relationship is analyzed for isothermal monotonic tensile testing...

  15. Hydrogen absorption characteristics of amorphous LaNi[sub 5. 0] films prepared by reactive sputtering

    SciTech Connect (OSTI)

    Sakaguchi, H.; Tsujimoto, T.; Adachi, Ginya (Osaka University, Suita (Japan))

    1993-01-01

    Amorphous LaNi[sub 5] thin films are expected to be one of the promising materials for use in hydrogen separation and battery electrodes, because the durability of the films is great in regard to the hydrogen absorption-desorption cycling process and the films have excellent resistance to harmful impurities in the hydrogen gas in comparison with the crystalline bulk material. An amorphous LaNi[sub 5.0] film having high hydrogen density and low hydrogen-induced stress was obtained by means of a reactive sputtering method using an Ar-H[sub 2] gas mixture. Pressure-composition isotherms show that the amount of hydrogen (H/LaNi[sub 5.0]) taken up by a formula weight of LaNi[sub 5.0] is about 1.5 times larger for the reactive sputtered film than for the conventional sputtered film prepared by using Ar gas. 18 refs., 1 fig, 1 tabs.

  16. Magnetism of NiMn2O4-Fe3O4 spinel interfaces

    E-Print Network [OSTI]

    Nelson-Cheeseman, B. B.

    2007-01-01

    2 O 4 –Fe 3 O 4 spinel interfaces B. B. Nelson-Cheeseman,isostructural spinel-spinel interface of NiMn 2 O 4 (NMO)–Feis preserved, both bulk and interface sensitive measurements

  17. Relaxation and critical strain for maximum In incorporation in AlInGaN on GaN grown by metal organic vapour phase epitaxy

    SciTech Connect (OSTI)

    Reuters, Benjamin; Finken, M.; Wille, A.; Kalisch, H.; Vescan, A.; Hollaender, B.; Heuken, M.

    2012-11-01

    Quaternary AlInGaN layers were grown on conventional GaN buffer layers on sapphire by metal organic vapour phase epitaxy at different surface temperatures and different reactor pressures with constant precursor flow conditions. A wide range in compositions within 30-62% Al, 5-29% In, and 23-53% Ga was covered, which leads to different strain states from high tensile to high compressive. From high-resolution x-ray diffraction and Rutherford backscattering spectrometry, we determined the compositions, strain states, and crystal quality of the AlInGaN layers. Atomic force microscopy measurements were performed to characterize the surface morphology. A critical strain value for maximum In incorporation near the AlInGaN/GaN interface is presented. For compressively strained layers, In incorporation is limited at the interface as residual strain cannot exceed an empirical critical value of about 1.1%. Relaxation occurs at about 15 nm thickness accompanied by strong In pulling. Tensile strained layers can be grown pseudomorphically up to 70 nm at a strain state of 0.96%. A model for relaxation in compressively strained AlInGaN with virtual discrete sub-layers, which illustrates the gradually changing lattice constant during stress reduction is presented.

  18. DISSERTATION DEVICE PHYSICS OF Cu(In,Ga)Se2 THIN-FILM SOLAR CELLS

    E-Print Network [OSTI]

    Sites, James R.

    OF Cu(In,Ga)Se2 THIN-FILM SOLAR CELLS Thin-film solar cells have the potential to be an important contributor to the global energy demand by the mid-21st-century. Cu(In,Ga)Se2 (CIGS) solar cells, which haveDISSERTATION DEVICE PHYSICS OF Cu(In,Ga)Se2 THIN-FILM SOLAR CELLS Submitted by Markus Gloeckler

  19. Investigation of photoexcited parallel conduction in GaAs/AlGaAs heterostructures in the quantum limit 

    E-Print Network [OSTI]

    Kobiela, Pawel Stanislaw

    1986-01-01

    conduction paths, one in the 2-DEG (medium 1) and the second an another medium (like AlGaAs), the conductivity tensor can be expressed as o' = rri + ap. Further analysis can be carried out by considering two separate limits: low and high magnetic fields.... The interval between the current pulses depended on the temperature and varied from 2-3 sec. at 10 K to about 1 min. at 15 mK. For each magnetic field scan between 0 and 7. 5 T about 500 readings were taken for l&oth current directions. As mentioned before...

  20. Experimental determination of band offsets of NiO-based thin film heterojunctions

    SciTech Connect (OSTI)

    Kawade, Daisuke; Sugiyama, Mutsumi, E-mail: mutsumi@rs.noda.tus.ac.jp [Faculty of Science and Technology/Research Institute for Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda 278-8510 (Japan); Chichibu, Shigefusa F. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980–8577 (Japan)

    2014-10-28

    The energy band diagrams of NiO-based solar cell structures that use various n-type oxide semiconductors such as ZnO, Mg{sub 0.3}Zn{sub 0.7}O, Zn{sub 0.5}Sn{sub 0.5}O, In{sub 2}O{sub 3}:Sn (ITO), SnO{sub 2}, and TiO{sub 2} were evaluated by photoelectron yield spectroscopy. The valence band discontinuities were estimated to be 1.6?eV for ZnO/NiO and Mg{sub 0.3}Zn{sub 0.7}O/NiO, 1.7?eV for Zn{sub 0.5}Sn{sub 0.5}O/NiO and ITO/NiO, and 1.8?eV for SnO{sub 2}/NiO and TiO{sub 2}/NiO heterojunctions. By using the valence band discontinuity values and corresponding energy bandgaps of the layers, energy band diagrams were developed. Judging from the band diagram, an appropriate solar cell consisting of p-type NiO and n-type ZnO layers was deposited on ITO, and a slight but noticeable photovoltaic effect was obtained with an open circuit voltage (V{sub oc}) of 0.96?V, short circuit current density (J{sub sc}) of 2.2??A/cm{sup 2}, and fill factor of 0.44.

  1. Heat treatment of NiCrFe alloy to optimize resistance to intergrannular stress corrosion

    DOE Patents [OSTI]

    Steeves, Arthur F. (Schenectady, NY); Bibb, Albert E. (Clifton Park, NY)

    1984-01-01

    A process of producing a NiCrFe alloy having a high resistance to stress corrosion cracking comprising heating a NiCrFe alloy to a temperature sufficient to enable the carbon present in the alloy body in the form of carbide deposits to enter into solution, rapidly cool the alloy body, and heat the cooled body to a temperature between 1100.degree. to 1500.degree. F. for about 1 to 30 hours.

  2. Determination of mechanical properties of Ni-Cr-P amorphous alloys 

    E-Print Network [OSTI]

    Kondlapudi, Swaroop Kumar R

    1991-01-01

    DETERMINATION OF MECHANICAL PROPERTIES OF Ni-Cr-P AMORPHOUS ALLOYS A Thesis by SWAROOP KUMAR R. KONDLAPUDI 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 August 1991 Major Subject: Mechanical Engineering DETERMINATION OF MECHANICAL PROPERTIES OF Ni-Cr-P AMORPHOUS ALLOYS A Thesis by SWAROOP KUMAR R. KONDLAPUDI Approved as to style and content by I-t (, :()o . e, ~&am A. Wolfenden...

  3. High-temperature luminescence in an n-GaSb/n-InGaAsSb/p-AlGaAsSb light-emitting heterostructure with a high potential barrier

    SciTech Connect (OSTI)

    Petukhov, A. A., E-mail: andrey-rus29@rambler.ru; Zhurtanov, B. E.; Kalinina, K. V.; Stoyanov, N. D.; Salikhov, H. M.; Mikhailova, M. P.; Yakovlev, Yu. P. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)] [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

    2013-09-15

    The electroluminescent properties of an n-GaSb/n-InGaAsSb/p-AlGaAsSb heterostructure with a high potential barrier in the conduction band (large conduction-band offset) at the n-GaSb/n-InGaAsSb type-II heterointerface ({Delta}E{sub c} = 0.79 eV) are studied. Two bands with peaks at 0.28 and 0.64 eV at 300 K, associated with radiative recombination in n-InGaAsSb and n-GaSb, respectively, are observed in the electroluminescence (EL) spectrum. In the entire temperature range under study, T = 290-480 K, additional electron-hole pairs are formed in the n-InGaAsSb active region by impact ionization with hot electrons heated as a result of the conduction-band offset. These pairs contribute to radiative recombination, which leads to a nonlinear increase in the EL intensity and output optical power with increasing pump current. A superlinear increase in the emission power of the long-wavelength band is observed upon heating in the temperature range T = 290-345 K, and a linear increase is observed at T > 345 K. This work for the first time reports an increase in the emission power of a light-emitting diode structure with increasing temperature. It is shown that this rise is caused by a decrease in the threshold energy of the impact ionization due to narrowing of the band gap of the active region.

  4. Low-temperature charge transport in Ga-acceptor nanowires implanted by focused-ion beams

    E-Print Network [OSTI]

    Robinson, SJ

    2008-01-01

    Low-Temperature Charge Transport in Ga-Acceptor Nanowiresare highly nonlinear at low temperatures, and a thresholdmetallic conductance at low temperatures could be achieved

  5. Vacancy defects in as-grown and neutron irradiated GaP studied by positrons

    SciTech Connect (OSTI)

    Dlubek, G.; Bruemmer, O.; Polity, A.

    1986-08-18

    Positron lifetime and Doppler-broadening measurements have been used to study vacancy defects in n-italic-type GaP. Vacancies in the P sublattice with a concentration of some 10/sup 17/ cm/sup -3/ were observed in as-grwon GaP. The vacancies disappear during annealing at 500--800 /sup 0/C. In neutron-irradiated GaP positrons are trapped by Ga vacancies which anneal out in two stages situated at 300--550 /sup 0/C and 550--700 /sup 0/C.

  6. Structural defects in GaN revealed by Transmission Electron Microscopy

    SciTech Connect (OSTI)

    Liliental-Weber, Zuzanna

    2014-04-18

    This paper reviews the various types of structural defects observed by Transmission Electron Microscopy in GaN heteroepitaxial layers grown on foreign substrates and homoepitaxial layers grown on bulk GaN substrates. The structural perfection of these layers is compared to the platelet self-standing crystals grown by High Nitrogen Pressure Solution. Defects in undoped and Mg doped GaN are discussed. Some models explaining the formation of inversion domains in heavily Mg doped layers that are possible defects responsible for the difficulties of p-doping in GaN are also reviewed.

  7. Raman scattering in InAs/AlGaAs quantum dot nanostructures E. Giulotto,1,a

    E-Print Network [OSTI]

    As upper CL UCL with the same composition of LCL, and a 10 nm thick GaAs cap layer. Buffers and LCLs were

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

    SciTech Connect (OSTI)

    KLEM,JOHN F.; Blum, O.

    2000-08-17

    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.

  9. Interface Reactions and Electrical Characteristics of Au/GaSb Contacts

    SciTech Connect (OSTI)

    H. Ehsani; R.J. Gutmann; G.W. Charache

    2000-07-07

    The reaction of Au with GaSb occurs at a relatively low temperature (100 C). Upon annealing, a AuSb{sub 2} compound and several Au-Ga phases are produced. Phase transitions occur toward higher Ga concentration with increasing annealing temperatures. Furthermore, the depth of the contact also increases with increased annealing temperature. They found that the AuSb{sub 2} compound forms on the GaSb surface, with the compound crystal partially ordered with respect to the substrate. The transition of Schottky- to ohmic-contact behavior in Au/n-type GaSb occurs simultaneously with the formation of the AuGa compound at about a 250 C annealing temperature. This ohmic contact forms without the segregation of dopants at the metallic compound/GaSb interface. Therefore it is postulated that transition from Schottky- to ohmic-contact behavior is obtained through a series of tunneling transitions of electrons through defects in the depletion region in the Au/n-type GaSb contacts. Contact resistivities of 6-7 x 10{sup -6} {Omega}-cm{sup 2} were obtained with the annealing temperature between 300 and 350 C for 30 seconds. In Au/p-type GaSb contacts, the resistivity was independent of the annealing temperature. This suggested that the carrier transport in p-type contact dominated by thermionic emission.

  10. Slovaropisje klasi?nih jezikov na Slovenskem v 16. stoletju

    E-Print Network [OSTI]

    Hriberšek, Matej

    2008-02-01

    , da bi bil slovar pomagalo za dijake latinskih šol; nedvomno pa so ga intelektualci uporabljali pri svojem delu, dijaki pa pri u?enju. Drugi za Slovence pomemben slovaropisni dosežek je Megiserjev Thesaurus polyglottus (Zaklad ve? jezikov ali Slovar... in literarne vede. Ljubljana. Jože STABEJ, 1967: Za?etki slovenskega slovarstva v 16. stoletju. Jezik in slovstvo 12/6, 182–188. – –, 1977: Hieronymus Megiser: Thesaurus polyglottus. Iz njega je slovensko besedje z latinskimi in nemškimi pomeni za Slovensko...

  11. A comparison of the structure and localized magnetism in Ce{sub 2}PdGa{sub 12} with the heavy fermion CePdGa{sub 6}

    SciTech Connect (OSTI)

    Macaluso, Robin T. [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States); Millican, Jasmine N. [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States); Nakatsuji, Satoru [Department of Physics, Kyoto University, Kyoto, Japan 606-8502 (Japan); Lee, Han-Oh [Department of Physics, University of California, Davis, CA 95616 (United States); Carter, B. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Moreno, Nelson O. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Fisk, Zachary [Department of Physics, University of California, Davis, CA 95616 (United States); Chan, Julia Y. [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States)]. E-mail: jchan@lsu.edu

    2005-11-15

    Single crystals of Ce{sub 2}PdGa{sub 12} have been synthesized in Ga flux and characterized by X-ray diffraction. This compound crystallizes in the tetragonal P4/nbm space group, Z=2 with lattice parameters of a=6.1040(2)A and c=15.5490(6)A. It shows strongly anisotropic magnetism and orders antiferromagnetically at T{sub N}{approx}11K. A field-induced metamagnetic transition to the ferromagnetic state is observed below T{sub N}. Structure-property relationships with the related heavy-fermion antiferromagnet CePdGa{sub 6} are discussed.

  12. Origin of InGaN/GaN light-emitting diode efficiency improvements using tunnel-junction-cascaded active regions

    SciTech Connect (OSTI)

    Piprek, Joachim, E-mail: piprek@nusod.org [NUSOD Institute LLC, P.O. Box 7204, Newark, Delaware 19714 (United States)

    2014-02-03

    This Letter investigates the efficiency enhancement achieved by tunnel junction insertion into the InGaN/GaN multi-quantum well (MQW) active region of blue light emitting diodes (LEDs). The peak quantum efficiency of such LED exceeds 100%, but the maximum wall-plug efficiency (WPE) hardly changes. However, due to the increased bias, the WPE peaks at much higher input power, i.e., the WPE droop is significantly delayed, and the output power is strongly enhanced. The main physical reason for this improvement lies in the non-uniform vertical carrier distribution typically observed within InGaN MQWs.

  13. InGaP/GaAs Inverted Dual Junction Solar Cells For CPV Applications Using Metal-Backed Epitaxial Lift-Off

    SciTech Connect (OSTI)

    Bauhuis, Gerard J.; Mulder, Peter; Haverkamp, Erik J.; Schermer, John J.; Nash, Lee J.; Fulgoni, Dominic J. F.; Ballard, Ian M.; Duggan, Geoffrey

    2010-10-14

    The epitaxial lift-off (ELO) technique has been combined with inverted III-V PV cell epitaxial growth with the aim of employing thin film PV cells in HCPV systems. In a stepwise approach to the realization of an inverted triple junction on a MELO platform we have first grown a GaAs single junction PV cell to establish the basic layer release process and cell processing steps followed by the growth, fabrication and test of an inverted InGaP/GaAs dual junction structure.

  14. 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.

    1998-11-24

    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.

  15. Experimental determination and thermodynamic modeling of the Ni-Re binary system

    SciTech Connect (OSTI)

    Yaqoob, Khurram [Chimie Metallurgique des Terres Rares (CMTR), Institut de Chimie et des Materiaux Paris-Est (ICMPE), 2-8 rue Henri Dunant, 94320 Thiais Cedex (France)] [Chimie Metallurgique des Terres Rares (CMTR), Institut de Chimie et des Materiaux Paris-Est (ICMPE), 2-8 rue Henri Dunant, 94320 Thiais Cedex (France); Joubert, Jean-Marc, E-mail: jean-marc.joubert@icmpe.cnrs.fr [Chimie Metallurgique des Terres Rares (CMTR), Institut de Chimie et des Materiaux Paris-Est (ICMPE), 2-8 rue Henri Dunant, 94320 Thiais Cedex (France)] [Chimie Metallurgique des Terres Rares (CMTR), Institut de Chimie et des Materiaux Paris-Est (ICMPE), 2-8 rue Henri Dunant, 94320 Thiais Cedex (France)

    2012-12-15

    The phase diagram of the Ni-Re binary system has been partially reinvestigated by chemical, structural and thermal characterization of the arc melted alloys. The experimental results obtained during the present investigation were combined with the literature data and a new phase diagram of the Ni-Re binary system is proposed. In comparison with the Ni-Re phase diagram proposed by Nash et al. in 1985 [1], significant differences in the homogeneity domains, freezing ranges and peritectic reaction temperature were evidenced. On the other hand, thermodynamic modeling of the studied system by using the new experimental information has also been carried out with the help of the CALPHAD method. The calculated Ni-Re phase diagram showed a good agreement with the selected experimental information. - Graphical abstract: Ni-Re phase diagram according to the present study. Highlights: Black-Right-Pointing-Pointer Re-investigation of the Ni-Re phase diagram. Black-Right-Pointing-Pointer Extended phase field of the hcp phase. Black-Right-Pointing-Pointer Different freezing ranges and peritectic reaction temperature. Black-Right-Pointing-Pointer Thermodynamic modeling of the studied system by using the CALPHAD method.

  16. An Update on Improvements to NiCE Support for RELAP-7

    SciTech Connect (OSTI)

    McCaskey, Alex; Wojtowicz, Anna; Deyton, Jordan H.; Patterson, Taylor C.; Billings, Jay Jay

    2015-01-01

    The Multiphysics Object-Oriented Simulation Environment (MOOSE) is a framework that facilitates the development of applications that rely on finite-element analysis to solve a coupled, nonlinear system of partial differential equations. RELAP-7 represents an update to the venerable RELAP-5 simulator that is built upon this framework and attempts to model the balance-of-plant concerns in a full nuclear plant. This report details the continued support and integration of RELAP-7 and the NEAMS Integrated Computational Environment (NiCE). RELAP-7 is fully supported by the NiCE due to on-going work to tightly integrate NiCE with the MOOSE framework, and subsequently the applications built upon it. NiCE development throughout the first quarter of FY15 has focused on improvements, bug fixes, and feature additions to existing MOOSE-based application support. Specifically, this report will focus on improvements to the NiCE MOOSE Model Builder, the MOOSE application job launcher, and the 3D Nuclear Plant Viewer. This report also includes a comprehensive tutorial that guides RELAP-7 users through the basic NiCE workflow: from input generation and 3D Plant modeling, to massively parallel job launch and post-simulation data visualization.

  17. Interplay between out-of-plane anisotropic L1{sub 1}-type CoPt and in-plane anisotropic NiFe layers in CoPt/NiFe exchange springs

    SciTech Connect (OSTI)

    Saravanan, P.; Hsu, Jen-Hwa Tsai, C. L.; Tsai, C. Y.; Lin, Y. H.; Kuo, C. Y.; Wu, J.-C.; Lee, C.-M.

    2014-06-28

    Films of L1{sub 1}-type CoPt/NiFe exchange springs were grown with different NiFe (Permalloy) layer thickness (t{sub NiFe}?=?0–10?nm). X-ray diffraction analysis reveals that the characteristic peak position of NiFe(111) is not affected by the CoPt-layer—confirming the absence of any inter-diffusion between the CoPt and NiFe layers. Magnetic studies indicate that the magnetization orientation of NiFe layer can be tuned through varying t{sub NiFe} and the perpendicular magnetic anisotropy of L1{sub 1}-type CoPt/NiFe films cannot sustain for t{sub NiFe} larger than 3.0?nm due to the existence of exchange interaction at the interface of L1{sub 1}-CoPt and NiFe layers. Magnetic force microscopy analysis on the as-grown samples shows the changes in morphology from maze-like domains with good contrast to hazy domains when t{sub NiFe}???3.0?nm. The three-dimensional micro-magnetic simulation results demonstrate that the magnetization orientation in NiFe layer is not uniform, which continuously increases from the interface to the top of NiFe layer. Furthermore, the tilt angle of the topmost NiFe layers can be changed over a very wide range from a small number to about 75° by varying t{sub NiFe} from 1 to 10?nm. It is worth noting that there is an abrupt change in the magnetization direction at the interface, for all the t{sub NiFe} investigated. The results of present study demonstrate that the tunable tilted exchange springs can be realized with L1{sub 1}-type CoPt/NiFe bilayers for future applications in three-axis magnetic sensors or advanced spintronic devices demanding inclined magnetic anisotropy.

  18. Metallic glass alloys of Zr, Ti, Cu and Ni

    DOE Patents [OSTI]

    Lin, Xianghong (Pasadena, CA); Peker, Atakan (Pasadena, CA); Johnson, William L. (Pasadena, CA)

    1997-01-01

    At least quaternary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10.sup.3 K/s. Such alloys comprise titanium from 19 to 41 atomic percent, an early transition metal (ETM) from 4 to 21 atomic percent and copper plus a late transition metal (LTM) from 49 to 64 atomic percent. The ETM comprises zirconium and/or hafnium. The LTM comprises cobalt and/or nickel. The composition is further constrained such that the product of the copper plus LTM times the atomic proportion of LTM relative to the copper is from 2 to 14. The atomic percentage of ETM is less than 10 when the atomic percentage of titanium is as high as 41, and may be as large as 21 when the atomic percentage of titanium is as low as 24. Furthermore, when the total of copper and LTM are low, the amount of LTM present must be further limited. Another group of glass forming alloys has the formula (ETM.sub.1-x Ti.sub.x).sub.a Cu.sub.b (Ni.sub.1-y Co.sub.y).sub.c wherein x is from 0.1 to 0.3, y.cndot.c is from 0 to 18, a is from 47 to 67, b is from 8 to 42, and c is from 4 to 37. This definition of the alloys has additional constraints on the range of copper content, b.

  19. Electrochemical Testing of Ni-Cr-Mo-Gd Alloys

    SciTech Connect (OSTI)

    T. E. Lister; R. E. Mizia; H. Tian

    2005-10-01

    The waste package site recommendation design specified a boron-containing stainless steel, Neutronit 976/978, for fabrication of the internal baskets that will be used as a corrosion-resistant neutron-absorbing material. Recent corrosion test results gave higher-than-expected corrosion rates for this material. The material callout for these components has been changed to a Ni-Cr-Mo-Gd alloy (ASTM-B 932-04, UNS N06464) that is being developed at the Idaho National Laboratory. This report discusses the results of initial corrosion testing of this material in simulated in-package environments that could contact the fuel baskets after breach of the waste package outer barrier. The corrosion test matrix was executed using the potentiodynamic and potentiostatic electrochemical test techniques. The alloy performance shows low rates of general corrosion after initial removal of a gadolinium-rich second phase that intersects the surface. The high halide-containing test solutions exhibited greater tendencies toward initiation of crevice corrosion.

  20. A novel theoretical model for broadband blue InGaN/GaN superluminescent light emitting diodes

    SciTech Connect (OSTI)

    Moslehi Milani, N.; Mohadesi, V.; Asgari, A.

    2015-02-07

    A broadband superluminescent light emitting diode with In{sub 0.2}Ga{sub 0.8}N/GaN multiple quantum wells (MQWs) active region is investigated. The investigation is based on a theoretical model which includes the calculation of electronic states of the structure, rate equations, and the spectral radiation power. Two rate equations corresponding to MQW active region and separate confinement heterostructures layer are solved self-consistently with no-k selection wavelength dependent gain and quasi-Fermi level functions. Our results show that the superluminescence started in a current of ?120?mA (?7.5?kA/Cm{sup 2}) at 300?K. The range of peak emission wavelengths for different currents is 423–426?nm and the emission bandwidth is ?5?nm in the superluminescence regime. A maximum light output power of 7.59 mW is obtained at 600?mA and the peak modal gain as a function of current indicates logarithmic behavior. Also, the comparison of our calculated results with published experimental data is shown to be in good agreement.