Cerium Oxide Buffer Layers on Perovskite-Type Substrates for Preparation of $c$-Axis-Oriented ${\rm YBa}_{2}{\rm Cu}_{3}{\rm O}_{7}$ Films by Fluorine-Free Metalorganic Deposition

Abstract

c-axis-oriented epitaxial YBa2Cu3O7-delta (YBCO) superconducting films were prepared on perovskite-type single crystal substrates, i.e., SrTiO3, LaAlO3, NdGaO3 and YAlO3 with cerium oxide (CeO2) buffer layers by fluorine-free metalorganic deposition (MOD) at relatively low heating rates. The YBCO films on these CeO2-buffered substrates exhibited high critical current densities with an average of 3-5 MA/cm2 at 77.3 K. Using CeO2 buffer layers we could avoid the occurrence of undesired a-axis-oriented grains of YBCO on these substrates despite employing lower heating rates. The lattice constants of YBCO films, CeO2 buffer and substrates were compared. It was found that both the YBCO films and CeO2 buffer were elastically deformed.