Preparation of Bi-Sr-Ca-Cu-O thin film by coevaporation and its thermal stability

Thin film with a high T/sub c/ single phase was prepared on a (100)MgO substrate at a substrate temperature of about 620 0C by coevaporation of Bi2O3, Sr, Ca, and Cu metal. The resistive superconducting transition with onset T/sub c/ of 80 K was observed for this film. By post-deposition annealing at 850 0C, the high T/sub c/ phase was transformed into a low T/sub c/ phase, while films annealed at a higher temperature such as 890 0C maintained the high T/sub c/ phase. These results indicated that the high T/sub c/ phase can exist only at the high-temperature region (∼890 0C) while the stable phase existing at the low-temperature region (∼850 0C) is the low T/sub c/ phase