Study of Nb‐based Josephson tunnel junctions

摘要

Nb‐based Josephson junctions are photographically fabricated with an improved lift‐off method. Aging properties of Nb/Pb junctions are studied and the possible origin of aging was pointed out, using the shape dependence and IJ‐H characteristics. The I‐V characteristics of Nb/Pb junctions were analyzed quantitatively using a proximity effect model based on McMillan’s tunneling model. Maximum Josephson current was calculated incorporating the strong coupling correction. Theory and experiment agreed well for both pair and quasiparticle density of states.