High-quality Nb-Si(asterisk)-Nb end Josephson junctions

Preliminary results are reported on the characteristics of end junctions made from refractory materials (niobium and polycrystalline silicon) fabricated by integrated-circuit technology. The normal resistance and characteristic voltage of the end junctions were measured versus the Si(asterisk) interlayer thickness, ranging from 3 to 12 nm; and typical volt-ampere characteristics were determined. The junctions are found to clearly exhibit the Josephson effect over the entire thickness range and thus over the entire range of critical current densities, from 50 to 500,000 A/sq cm. The structure of the interlayer is investigated.