Niobium step-edge superconducting junctions

摘要

Niobium junctions based on a step milled onto SiO2/ Si substrates were fabricated by patterning niobium thin films of thickness d = 25-200 nm to form step- edge junctions of height h = 25-200 nm and length L = 1.5-20 mu m. Measurements of the current-voltage (I-V) characteristics reveal a strong dependence on the ratio d/ h (0.25-5.3), with junctions changing from non- hysteretic to strongly hysteretic in I-V as d/ h changes from less than to greater than unity. The temperature dependence of I-c(T = 1.5-7 K) shows a step- like behavior that is indicative of complex vortex motion within the junctions.