Properties of niobium superconducting bridges prepared by electron-beam lithography and ion implantation

Abstract

Niobium superconducting bridges having a variable-thickness geometry consisting of a thin narrow implanted region joining two much thicker bulk films have been fabricated. The temperature dependence of the critical current is described well by the static theory of Likharev and Yakobson. The direct current and alternate current Josephson effects were observed at temperatures above the transition temperature T′c of the bridge. The magnetic field period of the ’’diffraction pattern’’ dependence on magnetic field is analyzed taking into account demagnetizing effects in an approximate way. This field period Hp is found as a function of the bridge width w and the length L for wide bridges (w/L≫1), i.e., Hp= (Φ0/μ0)/ 22/3w5/3L1/3.