EFFECTIVE SURFACE-RESISTANCE OF LUBA2CU3O7-DELTA THIN-FILMS

Superconducting LuBa2Cu3O7-delta thin films have been grown in situ on [100] LaAlO3 by pulsed laser deposition and their effective surface resistance, R(eff), has been measured at 10 GHz at various temperatures and for various thicknesses using microstrip resonator technique. The results show that the films are highly c-axis oriented with a high critical current density, J(c), in the range 4-5 X 10(6) A cm-2 at 77 K and a low value of intrinsic surface resistance R(s), of 320 muOMEGA for 10 GHz at 77 K. Thicker films (>3000 angstrom) however, have shown degraded values presumably due to the strain caused by the small ionic radius of lutetium which, as shown by Somasundaram et al. [Mater. Res. Bull. 25, 331 (1990)], makes LuBa2Cu3O7-delta unstable in bulk.