ALL YBA2CU3O7 JOSEPHSON EDGE JUNCTIONS WITH YBA2COCU2O7 AS THE BARRIER INSULATOR

A systematic investigation of all YBa2Cu3O7 edge junction ''shorts'', prepared with YBa2CoCu2O7 as the insulator but without the barrier fab rication step, using our in situ laser ablation deposition method is r eported. We find that the coupling across these junctions varies signi ficantly from a strong-link behavior (actual shorts) when the base ele ctrodes are thick (greater-than-or-equal-to 0.8 mum), to a typical wea k-link response when thinner bases are used (less-than-or-equal-to 0.2 mum). A model for the structure of the junctions is presented where t he base and the overlaying insulator layers are tapered at the edge. T his leads to a wedge type barrier which is thicker when the base is th inner. Coupling occurs at the tip region of this wedge which implies a ''wedge-edge'' geometry for the present junctions.