  Nb3Sn and V3Si thin films are promising candidates as thin films for the next
generation of superconducting radio-frequency (SRF) cavities. However,
sputtered films often suffer from stoichiometry and strain issues during
deposition and post annealing. In this study, we explore the structural and
chemical effects of thermal annealing, both in-situ and post-sputtering, on
DC-sputtered Nb3Sn and V3Si films of varying thickness on Nb or Cu substrates,
extending from our initial studies [1]. Through annealing at 950 {\deg}C, we
successfully enabled recrystallization of 100 nm thin Nb3Sn films on Nb
substrate with stoichiometric and strain-free grains. For 2 um thick films, we
observed the removal of strain and a slight increase in grain size with
increasing temperature. Annealing enabled a phase transformation from unstable
to stable structure on V3Si films, while we observed significant Sn loss in 2
um thick Nb3Sn films after high temperature anneals. We observed similar Sn and
Si loss on films atop Cu substrates during annealing, likely due to Cu-Sn and
Cu-Si phase generation and subsequent Sn and Si evaporation. These results
encourage us to refine our process to obtain high-quality sputtered films for
SRF use.

Materials Science;Superconductivity;Applied Physics