MEASUREMENTS OF THE THICKNESS DEPENDENCE OF THE SURFACE-RESISTANCE OF LASER ABLATED HIGH - TC SUPERCONDUCTING THIN-FILMS

We report on measurements of the surface resistance of thin Y1Ba2Cu3O7-x (YBCO) films made by laser ablation on SrTiO3. Several films were prepared with thicknesses ranging from 100 nm to 400 nm. The surface resistance of these films was measured automatically in a temperature range from 20 K to 90 K using a copper cavity at 66.8 GHz. The measured values quantitatively show the expected temperature dependence of the effective surface resistance R(eff) on the thickness of the superconducting films. From the measured R(eff) one can calculate the true surface resistance R(ST) by an analytical approximation, which takes into consideration substrate losses and multireflections within the film. Results show that within the measurement uncertainty R(ST) does not change with changing film thickness. At 77 K R(ST) values of about 15 m-OMEGA were measured, at 30 K R(ST) reached 9 m-OMEGA.