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

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