Factors affecting the microwave surface resistance of crack-free thick YBCO films on sapphire substrates

Abstract

We investigated the influence of the composition of YBCO film, deposited on sapphire 〈 R〉 substrates with CeO 2 buffer layers, on their microwave surface resistance. Y-rich YBCO films, 0.5-μm thick, deposited onto a 250-Å thick CeO 2 film showed good crystallinity, a smooth surface and low R s value. Results of the Hall constant measurement and the chemical state analysis infer that the composition deviation of the film from 1-2-3 stoichiometry to Y-rich does not produce defects, such as a second phase, and resulted in a small residual resistance which manifests itself in the microwave surface resistance measurement.