The complex conductivities of high Tc superconducting YBa2Cu3Ox thin films have been studied using the coplanar waveguide resonator technique. In order to evaluate the magnetic penetration depth precisely, we measured the temperature dependence of the resonant frequency and compared it with the numerical results self-consistently. The observed temperature dependence of the complex conductivities is shown to be able to distinguish the effects of the weaklink from the intrinsic property of the grain of an epitaxial thin film and demonstrate the weakly coupled grain model of YBa2Cu3Ox thin films.

We have studied an in situ edge preparation process and the effect of a substrate rotation during the edge preparation in order to improve the uniformity and electrical characteristics of high-Tc edge-type Josephson junctions. The improved YBa2Cu3Ox/PrBa2Cu3Ox/YBa2Cu3Ox edge junctions showed small 1σ-critical current spreads as low as 10% for 12 junctions. We have confirmed that the spreads do not increase significantly by adding groundplane over the junctions. In this paper, we will describe these processes developed for the fabrication of high-Tc superconducting integrated circuits.

YBa2Cu3Ox films were grown on MgO(100) substrates by liquid phase epitaxy. Their structural and electrical properties were examined. From TEM plan-view images, it is found that the film consists of large grains whose misorientation angles are less than 1. Although the DC critical current density values decrease with increasing the film thickness, the critical current density value of 9. 3105 A/cm2 at 77 K is obtained for a 7 µm-thick film. A microstrip resonator at 10. 8 GHz with a YBCO ground plane shows Q0 values of 14200 at 77 K and 23300 at 40 K, which correspond to surface resistance values of 650 and 400 µΩ, respectively. By using a microstrip line resonator with a Ti/Au ground plane, the critical field of the film at 77 K and 10. 8 GHz is estimated to be 30 Oe. The third-order intercept of the resonator with the Ti/Au ground plane is the input power of +43 dBm and the output power of +30 dBm at 77 K.

In the weakly coupled grain model which has been proposed to explain the residual surface resistance in high-Tc superconducting polycrystalline thin films, the superconducting polycrystalline thin films is described as a network of superconducting grains coupled via Josephson junctions. In order to evaluate this model we have fabricated the coplanar waveguide resonator using c-axis oriented YBa2Cu3Ox Thin Films and measured the residual surface resistance. The experimental results are in good agreement with theoretical prediction.

The capacitance and the resistance of the Au/PrBa2Cu3Oy (PBCO)/YBa2Cu3Ox (YBCO) structure were measured at liquid helium temperature. A film of YBCO was deposited by rf magnetron sputtering at 700, and its thickness was 250 nm. A film of PBCO was deposited by rf magnetron sputtering at 690, and its thickness was less than 375 nm. The inverse capacitance and the resistance of the structure increased with PBCO thickness when PBCO thickness was more than 70 nm. However, the inverse capacitance was near zero, and the resistance was much less than that of PBCO itself when PBCO thickness was less than 70 nm. These results show the possibility that the electric property of PBCO within 70 nm from the PBCO/YBCO interface is different from that of PBCO itself, that is, there is a low-resistance region in PBCO near the YBCO/PBCO interface.