Structure and Superconducting Properties of Bi-Sr-Ca-Cu-O Thin Films Annealed at Low Temperatures

Abstract
Thin films of the Bi-Sr-Ca-Cu-O system were prepared at substrate temperatures between 550°C and 600°C. The film deposited at 570°C showed an X-ray diffraction pattern of the high-T c phase without other phases and had a zero-resistance temperature T c at 23 K. After annealing at 570°C under the oxygen pressure of 1 atm, the zero-resistance T c increased to 47 K, but under the pressure of 0.1 atm, the crystal structure was changed and Ca-Cu-O phase appeared. On as-deposited films prepared by a low-temperature process, structure and superconducting properties are easily affected by low-temperature postannealing.