All a-axis oriented YBa2Cu3O(7-y) - PrBa2Cu3O(7-z) - YBa2Cu3O(7-y) Josephson devices operating at 80 K

The controllable, reproducible fabrication of nonhysteretic Josephson devices with excess-current weak-link characteristics at temperatures up to 80 K have been demonstrated. The devices are patterned from in situ deposited a-axis oriented YBa2Cu3O(7-y) - PrBa2Cu3O(7-y) - YBa2Cu3O(7-y) trilayers grown on SrTiO3(001) substrates. Control of the critical current density and resistance is achieved by varying the thickness of the PrBa2Cu3O(7-z) barrier layer. Critical current densities in excess of 10,000 A/sq cm have been reproducibly measured; good uniformity across the wafer is obtained with device parameters scaling with device area. Strong constant-voltage current steps are observed under 11.2 GHz microwave radiation at temperatures up to and above 80 K.