Properties of Nb3Sn films fabricated by magnetron sputtering from a single target

Superconducting Nb3Sn films were fabricated on sapphire and fine grain Nb substrates by magnetron sputtering from a single stoichiometric Nb3Sn target. The structural, morphological and superconducting properties of the films annealed for 24 h at temperatures of 800-1000 degrees C were investigated. The effect of the annealing time at 1000 degrees C was examined for 1, 12, and 24 h. The film properties were characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, energy dispersive X-ray spectroscopy, and Raman spectroscopy. The DC superconducting properties of the films were characterized by a four-point probe measurement down to cryogenic temperatures. The RF surface resistance of films was measured over a temperature range of 6-23 K using a 7.4 GHz sapphire-loaded Nb cavity. As-deposited Nb3Sn films on sapphire had a superconducting critical temperature of 17.21 K, which improved to 17.83 K when the film was annealed at 800 degrees C for 24 h. For the films annealed at 1000 degrees C, the surface Sn content was reduced to similar to 11.3% for an annealing time of 12 h and to similar to 4.1% for an annealing time of 24 h. The Raman spectra of the films confirmed the microstructural evolution after annealing. The RF superconducting critical temperature of the as-deposited Nb3Sn films on Nb was 16.02 K, which increased to 17.44 K when the film was annealed at 800 degrees C for 24 h.

Automated summary

Superconducting Nb3Sn films were fabricated using magnetron sputtering on different substrates, with the film properties characterized by various techniques and the effects of annealing at different temperatures studied. Results showed that appropriate annealing treatment can enhance the superconducting critical temperature of the films.