Niobium step-edge superconducting junctions

Abstract

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 µm. 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 Ic(T = 1.5–7 K) shows a step-like behavior that is indicative of complex vortex motion within the junctions.

Width and temperature dependence of hysteretic current–voltage character in long Niobium microbridges

“…With their simple geometry, superconducting microbridges have been widely studied [1][2][3][4][5][6] due to a variety of interesting electrical behaviors depending on their dimensions. The suppressed order parameter in the narrow constriction of short microbridges, for example, results in Josephson junction behavior [1,2].…”

“…The suppressed order parameter in the narrow constriction of short microbridges, for example, results in Josephson junction behavior [1,2]. Long microbridges are also important in view of their suitability for the study of fundamental resistive states near the transition temperature ðT c Þ of superconductors, and technological applications such as hot electron bolometers.…”