Single-Crystal YBa₂Cu₃O7-x Thin Films by Activated Reactive Evaporation

By means of the activated reactive evaporation, YBa 2 Cu 3 O 7- x single-crystal thin films with the c axis perpendicular to the substrate plane have been directly and epitaxially grown on the (100) surface of SrTiO 3 . The substrate temperature was kept below 600°C and the oxidation treatment was performed at below 500°C. The ac-resistive measurement for a film with 2000 Å thickness gave a sharp superconducting transition, where the endpoint was 90.2 K and Δ T c (10–90%)=1.7 K. From the complex susceptibility measurement we confirmed the Meissner effect as well as the structural uniformity of the specimen.