Ion beam machining of niobium weakly superconducting microbridges

Abstract

Superconducting microbridges of hard superconductors can be realized reproducibly using an ion bombardment technique. The micromachining is obtained directly by focussing onto the superconducting film a reduced ionic image which represents the structure to be machined. We describe and discuss the superconducting properties of niobium Josephson microbridges fabricated using this technique : critical temperature, normal resistance, I-V characteristic, dc magnetic field effect and microwave field effect. Microbridges with an operating temperature of 4.2 K have been realized