Bi-Sr-Ca-Cu-O film on sapphire grown by plasma-enhanced halide CVD

Plasma-enhanced halide chemical vapor deposition (CVD) for Bi-Sr-Ca-Cu-O (BSCCO) thin film has been developed. Superconducting BSCCO films were fabricated on 3-in-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 O ₂ and/or H₂O. The total pressure in the deposition chamber was 0.1 torr, and the O₂ partial pressure was 0.01 torr. Deposition was at 2 Å/min. It was found that the superconducting BSCCO film could be deposited on sapphire substrates at less than 700°C without a solid-phase reaction between the film and substrate and that plasma-enhanced CVD controlled the BSCCO phases even at 580°C. RF-plasma enhancement resulted in as-deposited superconducting BSCCO films. The c-axis orientation of the films was perpendicular to the sapphire´s (1102)-plane. The 700-Å-thick (2212)-phase BSCCO film showed that the resistive transition started at about 100 K and that the zero-resistivity temperature was 70 K. The critical current density was about 2.5×10⁶ A/cm² at 10 K