BI-SR-CA-CU-O FILM ON SAPPHIRE GROWN BY PLASMA-ENHANCED HALIDE CVD

We developed plasma-enhanced halide chemical vapor deposition (CVD) for Bi-Sr-Ca-Cu-O (BSCCO) thin film. Superconducting BSCCO films were fabricated on 3-inch diameter sapphire substrates without postannealing. The CVD apparatus has four source-gas generation cells in which source materials (BiCl3, SrI2, CaI2, and CuI) are evaporated or sublimated by heaters. Source gases are carried to the deposition chamber with helium. Oxidizing gases are O2 and/or H2O. The total pressure in the deposition chamber was 0.1 torr and the O2 partial pressure 0.01 torr. Deposition was at 2 angstrom/min. We found that the superconducting BSCCO film could be deposited on sapphire substrates at less than 700-degrees-C without a solid-phase reaction between the film and substrate, and that plasma-enhanced CVD controlled the BSCCO phases even at 580-degrees-C. RF-plasma enhancement resulted in as-deposited superconducting BSCCO films. The c-axis orientation of the films was perpendicular to the sapphire's (11 BAR02)-plane. The 700-angstrom-thick (2212)-phase BSCCO film showed that the resistive transition started at about 110 K and that the zero-resistivity temperature was 70 K. The critical current density was about 2.5x10(6) A/cm2 at 10 K.