Large-area sputtering of i n s i t u superconducting YBa2Cu3O7 films

Abstract

High-temperature superconducting thin films of YBa2Cu3O7 are deposited on 2 in. MgO and LaAlO3 substrates by radio frequency magnetron sputtering from an 8 in. diam powder target. By locating the substrate above the center of the magnetron erosion ring and by placing a ‘‘negative ion shield’’ between the target and the substrate, negative ion resputtering is avoided and high quality films are grown in situ, and are superconducting on removal from the vacuum chamber without a high-temperature post anneal. Stoichiometric films on LaAlO3 and MgO have critical temperatures up to 88 K and critical currents above 5×105 A/cm2 at 77 K. Uniformity in thickness of ±5%, and in room temperature resistivity of ±7% were measured on 2 in. diam substrates. Microwave surface resistance measurements at 1.2 GHz and 4.2 K showed Rs≊0.1 mΩ for YBCO ground planes and ≊0.3 mΩ for patterned YBCO strip lines on MgO.