All a-axis oriented YBa2Cu3O7-y-PrBa 2Cu3O7-z-YBa2Cu3O 7-y Josephson devices operating at 80 K

We have demonstrated the controllable, reproducible fabrication of nonhysteretic Josephson devices with excess-current weak-link characteristics at temperatures up to 80 K. The devices are patterned from in situ deposited a-axis oriented YBa2Cu3O7-y-PrBa 2Cu3O7-z-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 PrBa2Cu3O7-z barrier layer. Critical current densities in excess of 104 A/cm2 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.