Microwave Properties and Critical Current Density of YBCO Thin Films Deposited on CeO₂-Buffered Sapphire Substrates Using Sputtering Targets of Different Compositions

Abstract

The effect of the composition of a YBCO film on the microwave properties deposited on sapphire <R> substrates with a CeO2 buffer layer was investigated. CeO2 and YBCO films were deposited by RF magnetron sputtering with targets of different compositions. Y-rich crack-free YBCO films with a thickness of 0.5 µm, deposited onto a 25-nm-thick CeO2 film, showed good crystallinity and a low microwave surface resistance. Microwave surface resistances of 0.09 mΩ at 20 K and 0.7 mΩ at 77 K were obtained at a frequency of 12 GHz, and a critical current density of 0.1 MA/cm2 at 77 K was estimated for the 0.5-µm-thick YBa1.5Cu2.5O y film.