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  • 1
    Electronic Resource
    Electronic Resource
    Nonspiking ohmic contact to p-GaAs by solid-phase regrowth (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5714-5718 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A low-resistance and nonspiking contact consisting of a layered structure of Si/Ni(Mg) on p-GaAs is formed by solid-phase regrowth. Backside secondary-ion mass spectrometry and cross-sectional transmission electron microscopy show an initial reaction between Ni and GaAs to form NixGaAs which is later decomposed to form NiSi by reacting with the Si overlayer. This reaction leads to the solid-phase epitaxial regrowth of a p+ -GaAs layer doped with Mg. The total consumption of substrate is limited to a few hundred angstroms. The as-formed ohmic contact structure is uniform and planar with an average specific contact resistivity of ∼7×10−7 Ω cm2 on substrates doped to 8×1018 cm−3. The thermal stability of this contact scheme is also reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346990
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  • 2
    Electronic Resource
    Electronic Resource
    Superconducting YBa2Cu3O7−δ thin films with three different orientations (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4217-4220 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial thin films of YBaCuO have been prepared with (1) the a axis perpendicular to (100) SrTiO3 ; (2) the c axis perpendicular to (100) SrTiO3 ; and (3) the [110] axis perpendicular to (110) SrTiO3. Films were fabricated using a multilayer deposition technique involving three electron guns containing Y, BaF2, and Cu under a pressure of 5×10−5 Torr of O2. As deposited films, which contained polycrystalline and amorphous regions, were later annealed in a furnace under a flowing O2-H2 O atmosphere. X-ray diffraction patterns as well as scanning electron microscopy and high-resolution electron microscopy images confirm that the films are highly oriented, essentially epitaxial. The a-axis oriented film exhibits zero resistance at 90 K and a critical current density of 2.9×106 A/cm2 at 4.2 K while the c-axis oriented film exhibits a Tc of 88 K and a Jc of 0.9×107 A/cm2 at 4.2K; the Jc values were determined magnetically. The [110]-orientation film shows the sharpest transition with a transition width of 1 K and zero resistance at 85 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344932
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  • 3
    Electronic Resource
    Electronic Resource
    Ballooning stability of anisotropic, rotating plasmas (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 2346-2352 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The linearized equation of motion is given in a Lagrangian representation for a rotating plasma with anisotropic pressure. A WKB theory is developed for large-n ballooning modes in an axisymmetric configuration with field-aligned and rigid toroidal flows. In the presence of field-aligned flows, it is shown that a resonance occurs which is strongly suggestive of a generalized mirror instability. In the presence of toroidal rotation, a possible stabilizing effect is identified for P⊥〉P(parallel). Finally, as a special case of the theory, the necessary and sufficient conditions for stability in a static, anisotropic plasma are obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859499
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  • 4
    Electronic Resource
    Electronic Resource
    KrF laser-induced ablation and patterning of Y–Ba–Cu–O films (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2512-2514 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ablation and patterning of Y–Ba–Cu–O films on (100) SrTiO3 and (100) MgO substrates by KrF excimer-laser light projection was investigated. Three different regimes of laser-material interactions were observed. Transition temperatures and critical current densities in laser-fabricated strip lines were investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346519
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  • 5
    Electronic Resource
    Electronic Resource
    Antiferromagnetic form factor of Sr2CuO2Cl2 (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4524-4526 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Neutron diffraction techniques have been used to study the antiferromagnetic form factor of Sr2CuO2Cl2, which has the body-centered-tetragonal (I4/mmm) K2NiF4-type structure (the same as that of tetragonal La2CuO4 but with the out-of-plane oxygens replaced by Cl and the La by Sr). The antiferromagnetic form factor was obtained at 15 K by measuring the integrated intensities of the ( (1)/(2) (1)/(2) 0), ( (1)/(2) (1)/(2) 2), ( (1)/(2) (1)/(2) 3), ( (3)/(2) (3)/(2) 0), ( (3)/(2) (3)/(2) 6), ( (3)/(2) (5)/(2) 1), ( (3)/(2) (3)/(2) 8), and ( (5)/(2) (5)/(2) 0) magnetic reflections of a single crystal of Sr2CuO2Cl2. The experimentally determined magnetic form factor is similar to that of La2CuO4. The experimental data were compared with the Cu2+ magnetic form factor and with the results of band theoretical calculations. We find that the fit to the experimental data is improved if one assumes a dipolar spin polarization on the in-plane oxygen ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344857
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  • 6
    Electronic Resource
    Electronic Resource
    rf plasma aerosol deposition of superconductive Y1Ba2Cu3O7−δ films at atmospheric pressure (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1581-1583 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconducting films of Y1Ba2Cu3O7−δ were produced by a radio frequency (rf) plasma aerosol evaporation technique at atmospheric pressure. Aqueous solutions of the ions were generated as an aerosol and the mist was injected into the plasma region, and then deposited onto substrates outside of both the plasma and flame regions. The substrate temperature was about 600 °C. The deposition rate is 0.01–100 μm/(min cm2) and the film thickness is 1–200 μm. For an "as-deposited'' film on a single-crystalline MgO substrate (100), the onset temperature of the superconducting transition is 100 K, with a transition width (10–90%) of 3 K, and zero resistance at 91 K. For another film post annealed at 850±10 °C for 1 h, the onset temperature is 105 K, with a width of 6 K, and zero resistance at 91 K. Since this technique does not require a vacuum environment, it has potential for large scale production of thin films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104130
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  • 7
    Electronic Resource
    Electronic Resource
    Stable and shallow PdIn ohmic contacts to n-GaAs (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2129-2131 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A thermally stable, low-resistance PdIn ohmic contact to n-GaAs has been developed based on the solid phase regrowth mechanism [T. Sands, E. D. Marshall, and L. C. Wang, J. Mater. Res. 3, 914 (1988)]. Rapid thermal annealing of a Pd-In/Pd metallization induces a two-stage reaction resulting in the formation of a uniform single-phase film of PdIn, an intermetallic with a melting point greater than 1200 °C. A thin (∼5 nm) layer of average composition In0.4Ga0.6 As uniformly covers the interface between the PdIn layer and the GaAs substrate. Specific contact resistivities and contact resistances of ∼1×10−6 Ω cm2 and 0.14 Ω mm, respectively, were obtained for samples annealed at temperatures in the 600–650 °C range. The addition of a thin layer of Ge (2 nm) to the first Pd layer extends the optimum annealing temperature window down to 500 °C. Specific contact resistivities remained in the low 10−6 Ω cm2 range after subsequent annealing at 400 °C for over two days.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102993
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  • 8
    Electronic Resource
    Electronic Resource
    Structure of fluorescein dipropionate acetone solvate (1990)
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 46 (1990), S. 1676-1678 
    Details
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108270189012412
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  • 9
    Electronic Resource
    Electronic Resource
    Evidence for late Proterozoic subduction from 700-Myr-old blueschists in China (1990)
    [s.l.] : Nature Publishing Group
    Nature 346 (1990), S. 263-265 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Possible occurrences in the USSR and China of Precambrian blueschists have been reported7'13. Unfortunately these are not well documented because the data from the isotope analyses and the geological and petrographic descriptions were not provided. Although radiometric ages of 1,600, 1,100 and ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/346263a0
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  • 10
    Electronic Resource
    Electronic Resource
    Evolutionary analysis of Pinus densata Masters, a putative Tertiary hybrid (1990)
    Springer
    Theoretical and applied genetics 80 (1990), S. 635-640 
    Details
    ISSN: 1432-2242
    Keywords: Pinus ; Species hybridization ; Allozymes ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Allozyme differentiation at 13 loci was studied in populations of Pinus tabulaeformis, P. densata, and P. yunnanensis from China. It was previously suggested that P. densata represents a Tertiary hybrid between P. tabulaeformis and P. yunnanensis. The observed levels of allozyme variation within and among the investigated species were comparable to those of other conifers. P. tabulaeformis differed markedly from P. yunnanensis with respect to allozyme frequencies, while P. densata was intermediate between the two putative parents. There was evidence of homozygote excess in embryos from all investigated species, as compared to Hardy-Weinberg expectations. The observed allozyme composition of P. densata conformed to earlier morphological and molecular evidence indicating hybrid origin of this taxon. It was proposed that fusion of gene pools from P. tabulaeformis and P. yunnanensis has led to adaptive evolution of a new species, P. densata.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224223
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