Ex situ annealing effect on Nb thin films prepared by DC magnetron sputtering

Abstract

We studied effect of ex situ annealing on the superconductivity of Nb thin films on a silicon wafer prepared using DC magnetron sputtering. Fifty-nanometer thick Nb thin films were deposited using a 4-in. target under an Ar pressure of 7.5×10−3Torr with a DC power of 400W and then annealed at a base pressure of 4×10−6Torr in a separate chamber. The annealing process was performed at 50, 80, 100, 150, and 300°C for 15min. The properties of the annealed Nb thin films, including the superconducting transition temperature, were investigated. The results were analyzed in association with their structural changes as observed by X-ray diffraction and scanning electron microscopy.