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 r esistance, 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 cr itical 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 f or 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.