Structural and superconducting properties of Nb3Sn films grown by multilayer sequential magnetron sputtering

摘要

Nb3Sn thin films are fabricated by sequential sputtering followed by annealing at 850-1200 degrees C in vacuum. The effects of the annealing temperature and time on the formation of Nb3Sn were examined. The film crystal structure, morphology, surface topography and composition were characterized by X-ray diffraction, field-emission scanning electron microscopy, atomic force microscopy, and energy dispersive X-ray spectroscopy analysis. The superconducting properties of the films were characterized by measuring the surface resistivity by the four-point probe method. The highest critical temperature T-c = 17.86 K was observed for the Nb3Sn films annealed at 950 degrees C for 3 h. When the films were annealed above 1000 degrees C for 3 h, Sn evaporation resulted in a Nb-rich film, degrading the superconducting performance. Annealing at 1200 degrees C for 3 h resulted in evaporation of Sn leaving less than 1% Sn on the surface, as detected by energy dispersive spectroscopy, and for that film a T-c of 7.9 K was observed. (C) 2019 Elsevier B.V. All rights reserved.