Surface resistance of epitaxial YBa2Cu3O7 thin films on CeO2 diffusion barriers on sapphire

Epitaxial thin films of YBa2Cu3O7 (YBCO) have been deposited by off-axis sputtering onto substrates of r-plane sapphire coated with a CeO2 diffusion barrier which had been previously deposited by metalorganic chemical vapor deposition process. The YBCO films display excellent superconducting properties, with critical current densities and microwave surface resistances comparable to state of the art YBCO films deposited directly onto LaAlO3 or MgO substrates. The volume fraction of YBCO with large-angle in-plane misalignment relative to the underlying layers is comparable to, or smaller than that obtained for YBCO directly deposited onto MgO substrates.