Investigation of SrRuO₃ barriers in SNS junctions

High-quality films and multilayers of SrRuO₃ and YBa ₂Cu₃O₇ (YBCO) have been grown by off-axis sputtering. High-resolution transmission electron microscopy proved that the interface is atomically sharp. SNS junctions with SrRuO₃ barriers have been fabricated ex situ in an edge geometry, and in a sandwich geometry with both interfaces grown in situ. Supercurrents have been observed with barrier thicknesses from 10 to 40 nm, and Shapiro steps could be detected. In both junction geometries the normal resistance is several orders of magnitude higher, as would be expected from the resistance of the SrRuO₃ film, and shows a nonmetallic temperature dependence. An exponential dependence of the normal resistance upon the barrier thickness has been observed.