Preparation of superconducting YBa₂Cu₃O_7-x films by ecr plasma sputtering

Y-Ba-Cu-O films were prepared on (100)MgO single crystal substrates by ECR plasma sputtering. As-deposited films without substrate heating were amorphous and electrically insulating. The amorphous film was crystallized to YBa₂Cu₃O_7-x by postannealing at 930°C for 1 min in O₂ gas, and the T_c of the postannealed film was 70.5 K. The film prepared at the substrate temperature of 650°C was crystalline YBa₂Cu₃O_7-x and the T_c of the film without any postannealing was 73 K.