Development of ramp-edge sns junctions using highly stable normal-metal barrier materials

By using a cation-modified and corrosion-resistant compound of (Pr_yGd_0.6-y)Ca_0.4Ba_1.6La _0.4Cu₃O₇ (y = 0.4, 0.5, and 0.6) as normal-metal barrier materials, high-temperature superconducting Josephson junctions have been fabricated in a ramp-edge superconductor/normal-metal/superconductor (SNS) configuration. We have tuned the Pr substitution level in order to achieve the optimal electrical resistivity of the barrier layer for high-performance SNS junctions. The junctions fabricated with these normal-metal barriers show well-defined RSJ-like current \<s voltage characteristics at liquid-nitrogen temperature. The junction performance is mainly controlled by the N-layer instead of the interface. We have also fabricated dc superconducting quantum interference devices based on rampedge SNS technology with these normal-metal barriers. The ratio of peak-to-peak voltage modulation of the superconducting quantum interference devices to the ICR product is more than 30%.