Fabrication and measurement of submicron planar YBa/sub 2/Cu/sub 3/O/sub 7/ microbridge Josephson junctions

Deep-submicron planar YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO) microbridge Josephson junctions (about 0.1- mu m to 0.5- mu m long and wide) were fabricated using two different approaches: (1) using electron beam lithography and argon-ion milling to make the designed bridge pattern; and (2) depositing YBCO on a substrate with a prepatterned MgO/sapphire bilayer structure. Both approaches have yielded microbridges showing constant voltage steps in the current-voltage characteristics under applied microwave fields. The step width is also found to show oscillatory microwave power dependence. The possible mechanism for the Josephson-like behavior observed and the physical significance of these deep submicron bridges are discussed. The observed phenomena might be explained by the vortex motion model.<>