Co-doped-YBCO SNS junctions for superconductive integrated circuits

We have established a high temperature superconductor SNS junction fabrication process and are reproducibly fabricating junctions whose behavior is rooted in the physics of the proximity effect. SNS edge junctions are being fabricated using YBa/sub 2/Cu/sub 2.8/Co/sub 0.2/O/sub 7-/spl delta// (Co-YBCO) as the normal barrier, and YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) as the superconductor. In the small junction regime, the junctions have RSJ characteristics with I/sub c/R/sub n//spl sim/ 50 /spl mu/V at 77 K. Junction normal resistance values are consistent with known values of the barrier bulk resistivity and junction geometry, indicating that the interface resistance between YBCO and Co-YBCO is not significant. We have demonstrated I/sub c/ and R/sub n/ 1-/spl sigma/ spreads of 33% and 17%, respectively, for 6-junction strings. Barrier thickness and/or morphology variations appear to significantly contribute to these spreads. >