PVD growth and characterization of YBCO thin films on polycrystalline alumina substrates: phase separation

Ozenbas, MA
Gungoren, T
In this study, high T-c superconducting thin films of Y-Ba-Cu-O system have been prepared onto polycrystalline alpha -Al2O3 substrates by resistive evaporation of YF3, BaF2, and Cu powders and a subsequent multi-stage annealing. In the deposition process, two different methods were used: mixed-powder method and sequential-deposition method. The best quality films were achieved on alpha -Al2O3 substrates by using sequential-deposition technique with offset critical transition temperature of 80.6 K. Sequential deposition method seems to reduce film-substrate reactions on alpha -Al2O3 substrates, probably due in part to the prevention of phase separation.