Edge-geometry YBa/sub 2/Cu/sub 3/O/sub 7-x//Au/Nb SNS devices

The fabrication and electrical properties of edge-geometry YBaCuO/Au/Nb weak links are described. Superconductor/normal-metal/superconductor (SNS) devices of this type serve as sensitive probes of the electrical quality of the YBaCuO/Au interface. For device applications, the edge geometry has the advantage of placing the critical N/S device interface on the longer coherence length a-b surface, and it simplifies the fabrication of weak links with submicron dimensions. These structures are fabricated using laser-ablated, in situ, c-axis-oriented YBaCuO thin films, with both oxygen-annealed and unannealed YBaCuO/Au interfaces. The YBaCuO film edges are patterned using ion milling, followed by a low-energy-ion cleaning step and in situ deposition of Au and Nb. Devices with areas in the 10/sup -7/-10/sup -8/-cm/sup 2/ range have been fabricated with R/sub n/A products lower than 10/sup -8/ Omega -cm/sup 2/ and critical current densities up to 3 kA/cm/sup 2/. Josephson coupling is verified by the observation of microwave steps under 10-GHz microwave irradiation. The best results have been obtained with annealed YBaCuO/Au interfaces.