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  • 1
    Electronic Resource
    Electronic Resource
    NiGe-based ohmic contacts to n-type GaAs. II. Effects of Au addition (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 2530-2537 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Our efforts have been continued to improve the electrical properties of NiGe ohmic contacts by adding a small amount of a third element to the NiGe contacts without deteriorating thermal stability and surface smoothness. In the present study, Au was chosen as the third element, and the optimum conditions to produce thermally stable, low resistance ohmic contacts were determined by preparing a variety of contacts with different thickness ratios of the Ni, Ge, and Au layers. The best ohmic contact was prepared by depositing sequentially Ni (40 nm), Au (5 nm), and Ge (100 nm) onto the n-type GaAs substrate, and annealing at 450 °C for 5 s. This contact provided the contact resistance of about 0.2 Ω mm, which is lower than that of the NiGe(In) contacts. The present contact had smooth surface after contact formation and showed excellent thermal stability during isothermal annealing at 400 °C. The cross-sectional observation using high-resolution electron microscopy indicated that the GaAs/metal interface was uniform and the diffusion depth of the contact metal to the GaAs substrate was shallow (∼20 nm). These contact properties are desirable for future GaAs very large scale integration devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356226
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  • 2
    Electronic Resource
    Electronic Resource
    NiGe-based ohmic contacts to n-type GaAs. I. Effects of In addition (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 2522-2529 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Contact resistances of NiGe ohmic contacts, which had been previously developed in our laboratory, were reduced significantly by adding a small amount of In to the NiGe contacts without deteriorating the thermal stability, the surface smoothness, and the shallow diffusion depth. The optimum layer thicknesses to prepare the low resistance ohmic contacts were determined to be 60 nm for Ni, 100 nm for Ge, and 3 nm for In, and the contact resistances (Rc) less than 0.3 Ω mm were obtained after annealing at temperatures in the range between 600 and 700 °C. Microstructural analysis at the GaAs/metal interface of the contact with low Rc showed formation of "regrown'' GaAs and InxGa1−xAs layers between the GaAs substrate and high melting point NiGe compounds. Based on the present electrical measurements and microstructural analysis, a model for the current transport of the NiGe-based ohmic contacts was proposed, which explained well the dependencies of the contact resistances on the microstructure at the GaAs/metal interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356225
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  • 3
    Electronic Resource
    Electronic Resource
    Oxygen arrangement on Hg0.5Tl0.5Ba2CuOx (100) surface studied by high-resolution electron microscopy (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 2226-2228 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Oxygen arrangement on Hg0.5Tl0.5Ba2CuOx (100) surface was studied by high-resolution electron microscopy. The {100} planes were found to be stable and to have preferred atomic surface. A surface structure model of Hg0.5Tl0.5Ba2CuOx was proposed and compared to the image calculations, which indicated the surface consists of Ba layers and oxygen atoms on the (Hg, Tl) layers. The present work indicates that the stable {100} planes of Hg-1201-type superconducting oxides would be suitable for the future device application. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124972
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  • 4
    Electronic Resource
    Electronic Resource
    Shock-induced superconductivity of Tl2Ba2CuO6 (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 813-815 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Shock-loading experiments were done for as-prepared nonsuperconducting specimens of Tl2Ba2CuO6. The shocked specimens which were encased in the stainless-steel container with small holes exhibited a superconductivity of about Tc−75 K at 18 GPa, indicating that the overdoping state was released by oxygen loss during shock-loading. The x-ray powder diffraction pattern of the recovered specimens after shock-loading showed broadening of diffraction lines and a distortion to the orthorhombic symmetry. A transmission electron microscope image of the shocked specimen in which the orthorhombic distortion was observed in the x-ray powder diffraction patterns showed a twin structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104260
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  • 5
    Electronic Resource
    Electronic Resource
    Fivefold multiply-twinned precipitates in chemically vapour-deposited boron nitride studied by transmission electron microscopy (1989)
    Springer
    Journal of materials science 8 (1989), S. 130-134 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00730702
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  • 6
    Electronic Resource
    Electronic Resource
    Modulated structure of Ag2SnO3 studied by high-resolution electron microscopy (2000)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 363-368 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The modulated structure of Ag2SnO3, disilver tin trioxide, was investigated by high-resolution electron microscopy and electron diffraction along four different directions. Electron diffraction showed an incommensurate one-dimensional modulated structure with a modulation wavevector of 1/6.4a*. High-resolution images showed a large number of superstructure domains with the size range 10–100 nm and orientations related by hexagonal rotation. The modulation was determined to be displacements along the c axis of the Ag atoms both in octahedral and linear coordination. An approximate structure model with a commensurate sixfold superstructure, with an orthorhombic cell (P212121, a = 2.922, b = 1.267, c = 0.562 nm), is proposed. Calculated images and electron diffraction patterns, based on this model, agree well with experimental observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108768199013695
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  • 7
    Electronic Resource
    Electronic Resource
    High-resolution electron microscopy study on crystal structures of high-Tc superconductors (1989)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 12 (1989), S. 228-243 
    Details
    ISSN: 0741-0581
    Keywords: Y-Ba-Cu-O ; Bi-CA-Sr-Cu-O ; Atomic resolution analysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Recent studies of high-resolution electron microscopy on the high-Tc superconductors of Y-Ba-Cu-O and Bi-Ca-Sr-Cu-O are presented. The observed images of crystals thinner than 3 nm, taken under conditions that approached the Scherzer defocus condition, directly show the arrangements of cations and oxygen-vacant positions. The results reveal structural characteristics of the atomic scale; this offers important insights into the origin of the high-Tc superconductivity. The usefulness of high-resolution electron microscopy for studying complicated crystal structures is demonstrated for the high-Tc oxides.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060120306
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