Basic thin film deposition processes for the high-T_c superconductors of Bi-systems are described in relation to their structure and superconducting properties.
For the rare-earth high-T_c superconductors YBC the thin film deposition processes are clasified into three processes:
(i) deposition below crystallizing temperature followed by annealing [process (1)],
(ii) deposition above crystallizing temperatme followed by annealing [process (2)],
(iii) deposition above crystallizing temperature without postannealing [process (3)].
For the Bi-system there appear several superconducting phases including the low-T_c phase Bi₂Sr₂Ca₂Cu₂O_x and the high-T_c phase Bi₂Sr₂Ca₂Cu₃O_x. Thin films with these superconducting phases are synthesized by a selection of the substrate temperature T_s during the deposition in the process (1) and/or (2): The high-T_c phase with T_c ≈=110K is synthesized at T_s>800°C; the low-T_c phase with T_c=80K, at T_s<600°C. However, these films often comprise intergrowth structure between the differrent superconducting phases.
The close control of the supercondurting phase has been achieved by the layer-by-layer deposition in the atomic layer epitaxy process.