Characteristics of high critical current density Josephson junctions with Nb/AlO/sub x//Nb trilayers

We fabricated high critical current density (high J/sub c/) Josephson junctions, up to 47 kA/cm/sup 2/, consisting of Nb/AlO/sub x//Nb trilayers by use of high vacuum dc magnetron sputtering (less than 10/sup -6/ Pa). The relationship Jc/spl prop/(Pt)/sup -0.5/ can be obtained up to 47 kA/cm/sup 2/, where P and t are pressure and time, respectively, in oxidizing an Al surface. In the high J/sub c/ junctions, microshorts existed in Al surfaces. A property peculiar to most of the high J/sub c/ junctions was a step appearing at 1/3 gap voltage on their I-V curves. Magnetic field dependence of this step was different from that of a Fiske step.<
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