LARGE-AREA YBA2CU3O7 FILMS FOR HIGH-POWER MICROWAVE APPLICATIONS

We have developed large area YBa2Cu3O7 films (greater than or equal to 2 inch diameter) which have low microwave surface resistance at high microwave power levels. the films are produced by off-axis magnetron s puttering using a noncontact direct radiant heating technique. Thickne ss and composition are uniform to within +/-3% and T-c is uniform to w ithin +/-1 K across 3 inch diameter wafers. The microwave surface resi stance of these films has been measured over a wide range of temperatu re (20 K to 80 K) and microwave power. At 20 K, the surface resistance remains below 100 mu Omega (@ 10 GHz) or microwave surface current de nsities up to 4.6x10(6) A/cm(2). At 70 K, the surface resistance remai ns below 350 mu Omega (@ 10 GHz) for microwave current densities up to 1.3x10(6) A/cm(2). High power microwave transmission lines (14 mu m w ide) produced with these films are capable of transmitting microwave p ower up to +25 dBm (>2.3x10(6) A/cm(2) average current density) at 70 K.