As-grown superconducting Bi-Sr-Ca-Cu-O thin films by coevaporation

Superconducting Bi-Sr-Ca-Cu-O thin films have been prepared on (100) MgO substrates at about 600 °C by coevaporation. The c-axis lattice constant of this system was controlled to the values of 24–43 Å by changing film composition. Superconducting transition temperatures of these films were affected by substrate temperature and by a post-deposition annealing at a low temperature. The highest zero resistance temperature (Tc, zero) of the as-grown Bi2(Sr,Ca)3Cu2Ox film was 79 K. The best Bi2(Sr, Ca)4Cu3Ox film showed an onset temperature of 105 K and Tc, zero zero of 78 K after annealing at 400 °C for 1 h.