  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 {\deg}C were investigated. The
effect of the annealing time at 1000 {\deg}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 {\deg}C for 24 h. For the films
annealed at 1000 {\deg}C, the surface Sn content was reduced to ~11.3 % for an
annealing time of 12 h and 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
{\deg}C for 24 h.
