Hysteretic YBa/sub 2/Cu/sub 3/O/sub 7- delta /-Au- YBa/sub 2/Cu/sub 3/O/sub 7-/ delta proximity effect Josephson junctions

The superconducting proximity effect can be used to produce Josephson junctions in high-temperature superconducting structures with a normal conducting carrier. The authors describe work on edge-microbridge junctions made by defining 10-30- mu m-wide Au bridges to link the upper and lower layers of a YBa/sub 2/Cu/sub 3/O/sub 7- delta /Y/sub 2/O/sub 3/-YBa/sub 2/Cu/sub 3/O/sub 7- delta / trilayer. The structures are patterned by photolithography and ion milling from multilayers grown in situ by electron-beam evaporation. The best junctions operate up to around 20 K, exhibit hysteresis in their current-voltage characteristics, and have an I/sub c/R/sub N/ (critical-current normal-resistance product) greater than 200 mu V at 4.2 K. With a 400-nm-long microbridge, the maximum junction T/sub c/ observed was 25 K, and the largest I/sub c/R/sub N/ product at 4.2 K was 400 mu V. >