Preparation of YBa₂Cu₃O7-y Thin Films by Heat-Oxidation of Vacuum-Deposited Multilayer Metallic Films

YBa 2 Cu 3 O 7- y polycrystalline films have been prepared by heating the multilayer metallic films at 910°C in an oxygen atmosphere. The zero resistance temperature of 0.5 µm-thick YBa 2 Cu 3 O 7- y film is 88 K on SrTiO 3 (100) and 78 K on MgO(100) substrates. The electrical resistance of the film formed on an Al 2 O 3 (11̄02) substrate does not disappear at the solidification temperature of nitrogen (63 K). Impurity elements which diffused from the substrates into the superconductive thin films lower the critical temperatures. The crystallization mechanism is discussed based on the microstructural analysis.