The as Grown Superconductivity of Bi-Pb-Ca-Sr-Cu-0 Films Prepared by ac Sputtering

謝美樺(M. H. Hsieh) ； 楊鴻昌(H. C. Yang)

《Chinese Journal of Physics》 28卷3期 (1990/06) Pp. 287-292

並列摘要

Superconducting Bi-Pb-Ca-Sr-Cu-0 films were grown in situ by an ac sputtering technique. Two targets with the same composition were mounted in the electrodes of an ac sputtering system. The distance between the targets was 1.5 cm; the substrate was MgO(100). The sputtering was performed at a pressure of 200 mtorr using an Ar/O2(7:3) mixture by applying ~8-kV ac voltage (60 Hz) between the electrodes. The ac current in the sputtering was about 1.5 mA. During the ac sputtering, the sample was heated to about 630°C by a resistive heater. After sputtering in Ar/O2, the mixture of Ar/O2 gas was replaced by pure O2 kept at the same pressure (200 mtorr); the ac current and voltage were maintained at the same values. We found that the pure O2 plasma assists the incorporation of oxygen into the films. The films as grown have a black mirrored surface and show a superconducting transition temperature at 80 K (50% resistive transition) and zero resistance 70 K. The X-ray diffraction pattern shows a 2: 1:2:2 phase with c-axis perpendicular to MgO(100) surface.