Microwave properties and characterization of co-evaporated BSCCO thin films

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Abstract
An extensive characterization of Bi-Sr-Ca-Cu-O (BSCCO) thin films deposited by co-evaporation on LaAlO3 and SrTiO3 substrates has been performed. The films had a Tc(R=0) of approximately 78 K, and were predominantly c-axis oriented, with critical current densities (Jc) at 4.5 K of 1.6*106 and 1.1*106 A cm-2, for the samples on SrTiO3 and LaAlO3 respectively. The microwave properties of the films were examined by three techniques. The complex conductivity ( sigma *= sigma 1-j sigma 2) and the magnetic penetration depth ( lambda ) were measured by power transmission at 30.6 GHz; the surface resistance (RS) was measured using a cavity resonator at 58.9 GHz, and the transmission line losses were determined by measuring the quality factor (Q) of a linear microstrip resonator at 10.4 and 20.2 GHz. The complex conductivity for the film on LaAlO3 was determined to be (2.0-j10)*105 S m-1 at 77 K. It was observed that in the superconducting state sigma 1 deviates from both the Bardeen-Cooper-Schrieffer (BCS) theory and the two-fluid model. Values of lambda were found to be approximately 2.0 and 1.1 mu m at 77 K and 20 K respectively, and were obtained for the film on LaAlO3. The value of lambda at 20 K was approximately three times larger than that of BSCCO single crystals. RS values of 865 and 1391 m Omega were obtained for the films on SrTiO3 and LaAlO3, respectively, at 77 K and 58.9 GHz. Unloaded Q factors at 20 K of approximately 1100 and 800 at 10.4 and 20.2 GHz respectively, were measured for the BSCCO resonator. Unloaded Q values of 290 and 405 at 20 K were obtained at 10.4 GHz and 20.2 GHz respectively, for an all gold (Au) resonator.