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  • American Institute of Physics (AIP)  (2)
  • 1990-1994  (2)
  • 1970-1974
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  • 1
    Electronic Resource
    Electronic Resource
    Optical studies of PdO thin films (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4515-4522 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Palladium oxide thin films are studied by ellipsometry, optical transmission, and Raman scattering. The PdO films are made by completely oxidizing Pd films sputtered onto fused silica substrates, and their optical constants determined using a combination of ellipsometry and transmission measurements. Oxidation kinetics experiments are performed on thick Pd substrates at temperatures of 300–500 °C. The optical properties of the films show a thickness dependence suggesting an increased absorption at the PdO-Pd interface. Ellipsometry on oriented single crystals of PdO yields the anisotropic optical constants at 632.8 nm. These results are combined with an effective medium theory to show that the oxidized films have a void density of 20–25%. Raman scattering is demonstrated to be a very sensitive probe for detecting the presence of PdO on Pd. An oxide only a few A(ring) thick is readily detectable, despite the absence of any surface enhanced Raman effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350797
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  • 2
    Electronic Resource
    Electronic Resource
    Reactive codeposition of in situ Y-Ba-Cu-O superconducting films using dilute mixtures of ozone in oxygen (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1860-1867 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This investigation reports the effect of dilute additions of ozone in molecular oxygen on the limiting reactive gas pressures required for in situ deposition of YBa2Cu3O7−x thin films. Thermodynamic analysis indicates that the high oxidizing potential of ozone assures stability at equilibrium under virtually all experimental conditions of ozone pressure and substrate temperature. Thus the generation of a minor fraction of ozone in oxygen enables in situ deposition to be carried out without further enrichment at gas pressures well below those required in pure molecular oxygen. In situ superconductor deposition at various rates using coevaporated metals revealed a lower limit at an ozone-to-copper ratio of approximately unity. Superconducting films deposited at O3/Cu flux ratios above this threshold were highly (00l) oriented with critical temperatures of 87–90 K and critical currents of 2×106 A/cm2 that exhibited only small or ambiguous trends with increasing ozone above the threshold. Films deposited at O3/Cu ratios below the threshold were visually dissimilar (transparent-brown), semiconducting, and marked by conspicuous disappearance of the characteristic x-ray spectra. This threshold is a nonthermodynamic limit below which the supply of ozone is insufficient to maintain stoichiometry during continuous deposition. Since ozone molecules donate only single oxygen atoms in reaction, the observed limiting O3/Cu flux ratio supplies no more than one-half the total oxygen required to form tetragonal YBa2Cu3O6, which is the entry level phase for in situ deposition. It follows that molecular oxygen continues to function as a principal oxidant in reactive deposition even at reduced operating pressures given the stabilizing presence of ozone at a sufficient flux to elevate copper to its higher oxidation state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351171
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