Preparation and substrate reactions of superconducting Y-Ba-Cu-O films

Multiple metal-target dc magnetron sputter deposition of a metallic YBa2Cu3 alloy in pure Ar followed by ex situ oxygen annealing was used to prepare superconducting films on various substrates. This work particularly examines film-substrate reactions which are degrading to superconductivity. Better superconductors were obtained using predeposited buffer layers, notably on cubic zirconia and MgO substrates covered with Ag and Nb. Best films have Tc=80 K, metallic resistivities with resistance ratio≳2, and critical current density ≲10 kA cm−2 at 4.2 K. Normal-state resistivity measurements were made for O2 furnace temperatures up to 850 °C. Procedures for lithographically patterning these films are also described.