VOLTAGE-CURRENT CHARACTERISTICS AND NOISE PROPERTIES OF SNS JUNCTIONS

We report measurements of V/I/B characteristics for a number of YBCO/N/YBCO junctions where the N layer is Co doped YBCO. The field dependence of about half the junctions tested showed I-c/B characteristics which approached 100% modulation for T> 80K for field directions both perpendicular to the plane of the junction and along the width of the junction. Other junctions showed an anomalous field modulation which decreased as the temperature was increased. More detailed measurements are reported for one junction which showed fairly large field modulation. The V/I characteristics were found to be in very good agreement with a thermally rounded RSJ model in the temperature range 74-80K. The voltage noise peaked at I-c, and had a 1/f dependence in the range measured. It had a value of 8nV Hz(-1/2) at 1Hz and 75K.