Thin-film YBaCuO superconductors formed by Cu/BaO/Y₂O ₃ layer structures

Abstract

Thin-film superconductors of the YBaCuO family have been formed using layer structures of Cu, BaO, and Y2O3 deposited on different substrates by electron beam evaporation. Using a thickness ratio of Cu, BaO, and Y2O3 layers off that of the stoichiometric YBa 2Cu3O7 phase, superconducting films were formed on MgO and SrTiO3 substrates, with a Tc for zero resistance exceeding 77 K. The films were found to be composed of the superconducting YBa2Cu3O7 phase and the green Y2BaCuO7 phase, with the excessive Cu repelled to the surface in an oxidized form. The studies also provide information on the dependence of the superconducting transition on the annealing temperatures and the substrates used.