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  • 2000-2004  (12)
  • 1985-1989  (37)
  • 1
    Electronic Resource
    Electronic Resource
    Rapid laser-induced growth of nitride and oxide layers at a beryllium/liquid interface (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 293-295 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Excimer laser irradiation was used to induce rapid formation of nitride and oxide layers on beryllium samples immersed in liquid nitrogen and water, respectively. The elemental composition of the irradiated surfaces was determined by means of Rutherford backscattering spectrometry. Compound formation of Be3N2 and BeO was confirmed by x-ray diffraction. The results show that extensive reaction occurred only if the laser energy was sufficient to melt the beryllium surface. The amount of incorporated nitrogen or oxygen atoms was initially proportional to the laser energy density and to the number of laser shots. Saturation occurred when a near stoichiometric layer of Be3N2 or BeO was formed at the surface. The rate of compound formation was extremely high, on the order of 10–100 nm per shot.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339143
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Study of interdiffusion in a Te-doped AlAs-GaAs superlattice (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 2165-2167 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The enhanced layer interdiffusion in Te-doped AlAs/GaAs superlattices has been studied by secondary ion mass spectrometry. The superlattice sample was grown by organometallic chemical vapor deposition with Te doping at concentrations of 2×1017–3×1018 cm−3 during the growth process. In the temperature range from 800 to 1000 °C, the Al diffusion coefficient has an activation energy of 3.0 eV and is approximately proportional to the Te concentration. These results contrast sharply with Si-induced mixing which, in an analogous experiment, yielded an activation energy of 4.1 eV for the Al diffusion coefficient with a high power law dependence on the Si concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342848
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Substrate effects on the properties of Y-Ba-Cu-O superconducting films prepared by laser deposition (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 4591-4598 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconducting thin films of Y1Ba2Cu3Ox with superconducting transition temperature (Tc) near 90 K have been prepared by a laser deposition technique. We show that films prepared on sapphire, lithium niobate, and strontium titanate under identical processing conditions exhibit different electrical characteristics. The film surfaces, interfaces, and crystallinity have been studied by a number of analytical techniques. We conclude that the substrate influences the film properties primarily in three ways: the thermal expansion mismatch introduces cracks in the film, the interface reaction changes the film composition, and the substrate lattice influences the crystallographic orientation of the film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340136
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Columnar defect induced phase transformation in epitaxial La0.7Ca0.3MnO3 films (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4210-4215 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial La0.7Ca0.3MnO3 thin films on the SrTiO3(100) surface have been irradiated with 250 MeV Ag17+ ions at different nominal fluence values in the range of 5×1010–4×1011 ions/cm2, resulting in columnar defects. At low fluences these defects cause changes in material properties that are small and scale linearly with dosage. Above a threshold fluence value ∼3×1011 ions/cm2 dramatic changes are observed, including an order of magnitude increase in the resistivity and 50 K drop in the Curie temperature. Transmission electron microscopy measurements show that the changes are associated with a phase transformation of the undamaged region between the columnar defects. The transformed phase has a diffraction pattern very similar to that seen in charge-ordered La0.5Ca0.5MnO3. We propose that above a critical level of ion damage, strains caused by the presence of the columnar defects induce a charge-ordering phase transition that causes the observed dramatic changes in physical properties. We speculate that a conceptually similar surface-induced charge ordering may be responsible for the "dead layer" observed in very thin strained films, and the dramatic changes in optical properties induced by polishing, and that an impurity-induced charge ordering causes the extreme sensitivity of properties to lattice substitution. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373054
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Raman scattering investigation of a single-crystal-like YBa2Cu3O7−y film (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 4452-4453 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Room-temperature Raman spectra from a single-crystal-like film of YBa2Cu3O7−y fabricated by pulsed laser deposition are compared with similar spectra of a single crystal of YBa2Cu3O7−y. The comparison shows that not only is the axis perpendicular to the plane of the film, but that in addition the a-b axes are well oriented in the film plane. The data also show that the film is spatially uniform with respect to this orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343289
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Segregation of impurities in pulsed-laser-melted carbon (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1802-1809 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The segregation of 73Ge and 75As in pulsed-laser-melted carbon has been investigated. Both 73Ge and 75As were implanted into highly oriented pyrolytic graphite at a fluence of 1.0×1015 cm−2 at several energies. The implanted graphite was subsequently irradiated with a 30-ns pulsed ruby laser with laser pulse energy densities above the melt threshold for graphite. The distribution of impurities was measured before and after laser irradiation using Rutherford backscattering spectrometry to determine the redistribution of impurities resulting from diffusion in liquid carbon and segregation at the liquid-solid interface. Numerical calculations were then used to determine the diffusivity of the impurities in liquid carbon and the nonequilibrium segregation coefficient of Ge and As in carbon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341779
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  • 7
    Electronic Resource
    Electronic Resource
    A model for pulsed laser melting of graphite (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 4374-4382 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A model for laser melting of carbon at high temperatures to form liquid carbon has been developed. This model is solved numerically using experimental data from laser irradiation studies in graphite consistent with a melting temperature for graphite of 4300 K. The parameters for high-temperature graphite are based on the extension of previously measured thermal properties into the high-temperature regime. A simple classical free electron gas model is used to calculate the properties of liquid carbon. There is very good agreement between the model calculation and experimental results for laser pulse fluences below 2.0 J/cm2. Modifications to the model for larger laser pulse fluences are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335527
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  • 8
    Electronic Resource
    Electronic Resource
    Double heterostructure lasers with facets formed by a hybrid wet and reactive-ion-etching technique (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 2948-2950 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Double heterostructure lasers were fabricated in which one of the laser facets was produced by a hybrid wet and reactive-ion-etching technique. This technique is suitable for GaAs/GaAlAs heterostructure lasers and utilizes the selectivity of the plasma in preferentially etching GaAs over GaAlAs. Lasers fabricated by this technique are compatible with optoelectronic integration and have threshold currents and quantum efficiency comparable to lasers with both mirrors formed by cleaving. The technique enables the use of relatively higher pressures of noncorrosive gases in the etch plasma resulting in smoother mirror surfaces and further eliminates the nonreproducibility inherent in the etching of GaAlAs layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335235
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  • 9
    Electronic Resource
    Electronic Resource
    Imaging of current-induced superconducting-resistive transitions by scanning electron microscopy in laser-deposited superconducting thin films of Y1Ba2Cu3O7−x (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 911-913 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the transport current-induced resistive transitions in predominantly c-axis oriented crystalline Y1Ba2Cu3O7−x superconducting thin films with scanning electron microscopic (SEM) imaging and its correlation with dc current-voltage (I-V) measurements. We find that there is a nonlinear gradual transition region in the I-V curves that is caused by macroscopic effects (current "crowding'', substrate defects, film thickness variation, etc.) and by microscopic dissipation effects. At a high current there is an abrupt transition to the normal state in the I-V curve due to Joule heating. The SEM mapping provides a direct image of the above effects and is useful for characterization and study of fundamental transport properties of high Tc thin films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101620
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  • 10
    Electronic Resource
    Electronic Resource
    High critical currents in epitaxial YBa2Cu3O7−x thin films on silicon with buffer layers (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 754-756 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: As-deposited superconducting thin films (∼0.1 μm) of YBa2Cu3O7−x have been prepared by pulsed laser deposition on (100) Si with buffer layers of BaTiO3/MgAl2O4. X-ray diffraction studies reveal that the films grow epitaxially with the c axis preferentially oriented normal to the substrate surface. This is confirmed by ion channeling measurements along the (100) (normal to the surface) and (110) directions of the Si substrate showing a minimum yield of 54% along the (100), and 78% along the (110) axes using 2.8 MeV He++. Preliminary transmission electron microscopy study also supports these results. The as-deposited films have zero resistance temperatures of 86–87 K, and critical current densities of 6×104 A/cm2 at 77 K and 1.2×105 A/cm2 at 73 K. Our results indicate that the superconducting properties of the films are limited primarily by the quality and degree of epitaxal growth of the buffer layers on the silicon substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101471
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