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  • 1
    Electronic Resource
    Electronic Resource
    Dislocations and precipitates in gallium arsenide (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 620-629 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A complete dislocation analysis on a large number of grown-in dislocations was performed on wafers taken from three different semi-insulating liquid encapsulation Czochralski GaAs single crystals. By determining the Burgers vector, line direction, and habit plane of nearly 800 dislocations a decision could be made on dislocation type, dislocation generation, and multiplication mechanisms. Taking into account possible dislocation reactions between stress-induced glide systems all detected glide systems could be explained. The influence of post-growth annealing on both dislocations and arsenic precipitates was also investigated. Little effect was found on dislocations. Arsenic precipitates, however, showed a different distribution in size and significant effects on fine structure giving information on their nucleation and growth mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351346
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  • 2
    Electronic Resource
    Electronic Resource
    Low-resistivity epitaxial YBa2Cu3O7 thin films with improved microstructure and reduced microwave losses (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5572-5578 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial thin films of YBa2Cu3O7 have been prepared on SrTiO3 and LaAlO3 substrates by a high-pressure planar dc-sputtering technique. By covering the substrate heater with a frame of polycrystalline YBa2Cu3O7 substantial improvements of the YBa2Cu3O7 film properties were achieved. These are characterized by dc-resistivity values ρ(T) of less than 50 μΩ cm at 100 K and ρ(300 K)/ρ(100 K) values of up to 3.9. Significant deviations from the usual linear ρ(T) behavior were found. Critical temperatures above 90 K, resistive transition widths down to 0.3 K, and critical current densities of about 5 × 106 A/cm2 at 77 K confirm the high quality of the films. As indicated by Rutherford backscattering and high-resolution transmission electron microscopy the films exhibit a microstructure characterized by a reduced density of lattice defects. However, lattice-coherent precipitates with a diameter of about 5–10 nm were observed. As an outstanding feature the films exhibit, besides the initial steep falloff at Tc, a further gradual decrease of the microwave surface resistance at 87 GHz below 50 K by at least one order of magnitude. These results are very promising for millimeter-wave applications of epitaxial YBa2Cu3O7 thin films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350535
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  • 3
    Electronic Resource
    Electronic Resource
    Conservative antiphase boundary in SrTiO3 films on LaAlO3 substrates with SrRuO3 buffer layers (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5653-5656 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the microstructure of SrTiO3 films on LaAlO3 substrates with the SrRuO3 buffer layer using high-resolution transmission electron microscopy. While high density of defects due to lattice mismatch were found at the SrRuO3/LaAlO3 interface, no misfit dislocation was observed at the SrTiO3/SrRuO3 interface. The {111} stacking fault in the SrRuO3 buffer layer propagates into the SrTiO3 film, giving rise to a type of antiphase boundary on the {110} plane with a crystallographic shear vector of a/2〈001〉. The boundary is a conservative one which does not lead to any charge defects. A model based on dislocation interactions is proposed to explain the generation mechanism of the antiphase boundary. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1367881
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  • 4
    Electronic Resource
    Electronic Resource
    Evidence of point defect supersaturation during Zn diffusion in InP single crystals (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 2843-2845 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Formation of defects during Zn diffusion into undoped and semi-insulating Fe-doped InP single crystals at 700 °C was observed by transmission electron microscopy for various diffusion conditions. Agglomerates of predominantly perfect interstitial-type dislocation loops, dislocations, and small indium precipitates inside voids are observed in the Zn-diffused crystal region. In addition, large planar arrays of precipitates are formed by climbing dislocations. From these observations it is concluded that the incorporation of Zn on In sublattice sites creates a supersaturation of In self-interstitials which is relieved by dislocation loop formation leading to a supersaturation of P vacancies and void formation. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358698
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  • 5
    Electronic Resource
    Electronic Resource
    Low-noise dc superconducting quantum interference devices in Bi2Sr2CaCu2O8+x thin films (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 6703-6709 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-noise dc superconducting quantum interference devices (SQUIDs) were fabricated by thin film deposition of Bi2Sr2Ca Cu2O8+x (BSCCO) on bicrystalline substrates of SrTiO3 with misorientation angles aitch-theta from 24° to 45°. An optimized dc SQUID design (βL=1) was developed for aitch-theta=24°. Therein the SQUID inductance was varied between 7 and 80 pH. Fabricated dc SQUIDs operated at 77 K as well as high-quality YBa2Cu3O7−y (YBCO) SQUIDs, especially the 1/f and white noise levels were in the lowest range of data reported so far for YBCO SQUIDs and are two orders of magnitude better than noise data published this far for BSCCO SQUIDs at 77 K. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359084
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  • 6
    Electronic Resource
    Electronic Resource
    Structural transformations and strain relaxation mechanisms of In0.6Ga0.4As islands grown by molecular beam epitaxy on GaAs(001) substrates (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3824-3832 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The shape transformations and the mechanism of misfit strain relaxation of In0.6Ga0.4As islands grown at different temperatures on GaAs(001) substrates have been investigated. Layers with a constant nominal thickness of 12 monolayers were deposited by molecular beam epitaxy on nominal singular and on vicinal substrates. The specimens were characterized by scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy. It is shown that an increase of the growth temperature yields a shape transition from rounded islands to elongated cigar-like structures. The lattice-parameter mismatch in the circular islands is relaxed by misfit dislocations at lower growth temperatures. Indium desorption effectively reduces the mismatch at higher growth temperatures and therefore yields the nucleation of coherent islands. In spite of this structural transformation an Arrhenius-like behaviour of the island densities is observed with an activation energy which depends on the substrate tilt. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359897
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  • 7
    Electronic Resource
    Electronic Resource
    Correlation of YBa2Cu3O7 step-edge junction characteristics with microstructure (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1131-1139 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Current-voltage characteristics, Josephson radiation spectra, and critical current versus magnetic-field dependences were measured in epitaxial, c-axis YBa2Cu3O7 step-edge Josephson junctions (SEJs) on SrTiO3 and LaAlO3 substrates with various step angles α. The results were correlated with microstructural data to determine the origin of the observed weak-link behavior. It was shown that on steps with α(approximately-greater-than)45° the SEJ is a series connection of two weak links unambiguously correlated with the occurrence of two 90° tilt grain boundaries. On steep steps, α≥70°, the boundary at the upper step edge has, on average, the (103) symmetry, while the lower one is predominantly of the basal-plane-faced (010)(001) type. Correspondingly, one link is weaker than the other, with the weaker link originating on the (010)(001) boundary. However, others have shown that analogous grain boundaries in planar (103) and biepitaxial a-axis/c-axis films do not exhibit a strong magnetic-field dependence of critical current, which is characteristic of a weak link. Hence, it is proposed that the weak-link behavior of boundaries on step edges originates from their defect structure. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360347
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  • 8
    Electronic Resource
    Electronic Resource
    Millimeter-wave Hilbert-transform spectroscopy with high-Tc Josephson junctions (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1561-1563 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The application of Hilbert-transform spectroscopy for the measurement of high-harmonic content of the radiation from a frequency multiplier has been demonstrated in the spectral range from 60 to 450 GHz. YBa2Cu3O7−x grain-boundary Josephson junctions made on (110) NdGaO3 bicrystal substrates have been used in these experiments. The internal Josephson radiation of the junctions reveals a Lorentzian shape due to thermal noise broadening. The possibility to obtain a spectral resolution as low as 280 MHz (∼0.01 cm −1) has been shown with a Josephson junction operating at liquid-nitrogen temperature. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115699
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  • 9
    Electronic Resource
    Electronic Resource
    Formation of quasicrystals by mechanical alloying (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 117-119 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quasi-crystalline Al65Cu20Mn15 powder has been produced by mechanical alloying from crystalline elemental powders. The alloying process has been monitored by x-ray diffraction, and the resulting product has been characterized by transmission electron microscopy. The quasi-crystalline phase forms after about 90 h of milling. The crystallization temperature and enthalpy have been determined by differential scanning calorimetry. The results are compared with data for melt-spun material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102394
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  • 10
    Electronic Resource
    Electronic Resource
    Glass-forming range in mechanically alloyed Ni-Zr and the influence of the milling intensity (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 3224-3228 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Amorphous Ni-Zr powders have been prepared by mechanical alloying from crystalline elemental powders. The glass-forming range has been determined by x-ray diffraction, differential scanning calorimetry and saturation magnetization measurements. From 27 to 83 at. % Ni the powders become amorphous. This shows that deep eutectics do not play any role, contrary to amorphization by melt spinning. Crystallization temperatures, crystallization enthalpies, and wave numbers Qp, obtained from x-ray diffraction investigations, are compared with the data received for rapidly quenched samples. In addition, the effect of the milling intensity on the glass formation has been studied for the first time. If the intensity is too high, crystalline intermetallic phases are formed. On the other hand, the powder needs an extended milling time to become completely amorphous if the milling intensity is too low. Conclusions on the actual temperature of the individual particle during mechanical alloying and on the glass-forming process are drawn from these results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341540
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