TEMPERATURE-DEPENDENCE AND MAGNETIC-FIELD MODULATION OF CRITICAL CURRENTS IN STEP-EDGE SNS YBCO/AU JUNCTIONS

We compare the electrical transport properties of superconductor-normal metal-superconductor SNS step-edge YBCO/Au junctions where the Au is deposited at 100 degrees C and 600 degrees C. For both types of junctions we observe resistively shunted junction current-voltage characteristics. The critical currents I-c in all cases are similar for a given ratio of YBCO thickness-to-step height, while the normal resistance R(n) for the Au deposited at 600 degrees C is consistently 25% lower than for the Au deposited at 100 degrees C. The normalized temperature dependence of the I(c)R(n) product is nearly identical for all junctions with Au deposited at high temperatures but varies among junctions on a single chip for Au deposited at 100 degrees C. Low magnetic field modulation of the critical current can show either the expected Fraunhofer-like pattern or a double-junction modulation for both types of devices. The modulation period is consistently a factor of 3 lower for the high-temperature deposited Au.