Evaluation of magnetic penetration depth and surface resistance of superconducting thin films using coplanar waveguides

We have proposed a method to evaluate the magnetic penetration depth and the surface resistance of superconducting thin films from the kinetic inductance measurement using coplanar waveguides. The method utilizes the coplanar waveguide resonator where the temperature dependence of the resonant frequency due to the kinetic inductance is measured. Comparison between the observed data and an analytical expression using a conformal mapping technique gives the value of the magnetic penetration depth. The magnetic penetration depth of NbN thin films obtained in this way is shown to be in excellent agreement with that estimated from the dirty limit theory using resistivity and critical temperature. By applying this method to a YBaCuO resonator, we obtained the magnetic penetration depth /spl lambda/(0)=266 nm for a c-axis oriented film. Using the two-fluid model it is also shown that the surface resistance of the film can be evaluated from the quality factor and the kinetic inductance. We obtained the residual surface resistance Rs(0)=20 /spl mu//spl Omega/ at a frequency of 3.8 GHz.<
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