Regulation of superconductivity in Nb thin films induced by interstitial oxygen atoms

The regulation of superconductivity in thin films can provide important information on low-dimensional superconducting properties, and also has important reference values for the application in superconducting devices. Herein, we report the successful regulation of both the superconductivity and normal-state properties of Nb films in a wide range by the controllable introduction of interstitial oxygen atoms. The lattice parameter is enhanced for an extent as large as 4.4%, and the normal-state resistivity ρ_n is tuned for more than 15 times. The slope of upper critical field near T_c shows a close correlation with ρ_n in a wide range. Importantly, it is found that the suppression of T_c by disorder reveals a linear dependence with ρ_n in the region with an unchanged crystalline quality, which can be understood based on the picture of three-dimensional ballistic motion.