EVALUATION OF MAGNETIC PENETRATION DEPTH AND SURFACE-RESISTANCE OF SUPERCONDUCTING THIN-FILMS USING COPLANAR WAVE-GUIDES

We have proposed a method to evaluate the magnetic penetration depth a nd the surface resistance of superconducting thin films from the kinet ic inductance measurement using coplanar waveguides. The method utiliz es the coplanar waveguide resonator where the temperature dependence o f the resonant frequency due to the kinetic Inductance is measured. Co mparison between the observed data and an analytical expression using a conformal mapping technique gives the value of the magneic penetrati on depth. The magnetic penetration depth of NbN thin films obtained in this way is shown to be in excellent agreement with that estimated fr om the dirty limit theory using resistivity and critical temperature. By applying this method to a YBaCuO resonator, we obtained the magneti c penetraion depth lambda(0)=260 nm for a c-axis oriented film. Using the two-fluid model it is also shown that the surface resistance of th e film can be evaluated from the quality factor and the kinetic induct ance. We obtained the residual surface resistance Rs(0)=20 mu Omega at a frequency of 3.8 GHz.