YBa/sub 2/Cu/sub 3/O/sub 7- delta //Au/Nb sandwich geometry SNS weak links on c-axis oriented YBa/sub 2/ Cu/sub 3/O/sub 7- delta /

摘要

Sandwich geometry superconductorormal metal/superconductor structures have been fabricated on LaAlO/sub 3/ and cubic zirconia with laser-ablated, c-axis-oriented YBa/sub 2/Cu/sub 3/O/sub 7- delta / base electrodes, 100-600 AA of Au, and Nb counter electrodes, all formed in situ without breaking vacuum. Junctions range in size from 5 to 50 mu m on a side. Four probe I-V measurements at 4.2 K show R/sub n/A products as low as 6*10/sup -9/ Omega cm/sup 2/ and critical current densities up to 5.2 kA/cm/sup 2/. AC Josephson steps were observed with the application of 10-GHz radiation. The temperature dependence of J/sub c/ and the observation of the AC Josephson effect suggest that true supercurrents are present and that they do indeed represent the characteristics of the YBa/sub 2/Cu/sub 3/O/sub 7- delta //Au/Nb structure. The best results were obtained when the devices were annealed at approximately 450 degrees C in O/sub 2/ for 30 min after Au deposition.