Superconducting Bi-Sr-Ca-Cu-O Thin Films by Sputtering

Abstract

BiSrCaCu 2 O x thin films were prepared by rf magnetron sputtering. Superconducting transitions were observed for the films on MgO after postdeposition annealing at 870°C and above. The appearance of a superconducting transition at a temperature of about 120 K for the film necessitated annealing at close to, but not above, its melting point near 900°C: the appropriate annealing temperature range was from 875 to 900°C. It was noteworthy that the 910°C annealed film showed a superconducting characteristic as well as the 870°C annealed film, in spite of their crystal structures being entirely different. Besides annealing temperature, cooling rate from annealing temperature, film thickness and substrate dependences of superconductivity in the BiSrCaCu 2 O x thin film were also investigated.