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Proceedings Paper

In-Situ Fabrication, Processing And Characterization Of Superconducting Oxide Films
Author(s): A. I. Braginski; J. Talvacchio; J. R. Gavaler; M. G. Forrester; M. A. Janocko
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Paper Abstract

Surfaces of Y1Ba2Cu3O7 (YBCO) are known to react with H2O and CO2 in the ambient atmosphere. The in-situ approach to thin film fabrication and characterization in a closed system makes it possible to investigate the near-surface properties of superconducting YBCO films in the absence of such deleterious reactions. We have fabricated and analyzed superconducting, epitaxial YBCO films entirely or partly in-situ. Oxygen partial pressures during deposition ranged from < 10-9 torr to > 3 X 10-4 torr and temperatures from 400 to > 650°C, producing either amorphous or crystalline deposits. We found that annealing of oxygen-deficient amorphous deposits in oxygen caused atomic segregation of Ba and Y to the surface with a corresponding depletion in Cu. This effect made near-surface layers nonsuperconducting even in the absence of H2O or CO2. Fast heating to crystallization temperature minimized the segregation. Measurements of dc contact resistance, R , and I-V characteristics in cross-strip junctions of YBCO/Au/Nb and YBCO/Au/MgO/Nb indicated near-zero Rc and weak-link I-V characteristics which proved that the in-situ approach permits one to obtain superconducting YBCO film surfaces. In the case of crystalline film deposition at 650°C, the in-situ electron-diffraction of SrTiO3 substrates and 40 to 100 Å thick YBCO films revealed epitaxial crystallization only on clean substrates.

Paper Details

Date Published: 23 August 1988
PDF: 10 pages
Proc. SPIE 0948, High-Tc Superconductivity: Thin Films and Devices, (23 August 1988); doi: 10.1117/12.947476
Show Author Affiliations
A. I. Braginski, Westinghouse R&D Center (United States)
J. Talvacchio, Westinghouse R&D Center (United States)
J. R. Gavaler, Westinghouse R&D Center (United States)
M. G. Forrester, Westinghouse R&D Center (United States)
M. A. Janocko, Westinghouse R&D Center (United States)

Published in SPIE Proceedings Vol. 0948:
High-Tc Superconductivity: Thin Films and Devices
Cheng-Chung John Chi; R. Bruce van Dover, Editor(s)

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