Barrier composition and electrical properties of high-quality all-niobium Josephson tunnel junctions

A fabrication procedure for all-niobium tunnel junctions with oxide tunnel barriers is described. All steps of the tunnel-barrier growth have been characterized in situ with the help of x-ray photoelectron spectroscopy. The chemical composition of the barrier is described, and the properties of devices discussed. The results demonstrate the application potential of these all-refractory junctions.