Kinetically induced low-temperature synthesis of Nb₃Sn thin films

Nb₃Sn thin films are promising candidates for future application in superconducting radio frequency cavities due to their low surface resistivity, high critical temperature, and critical field, as compared to bulk niobium, which is the current state of the art. In this paper, we report the deposition of Nb₃Sn thin films by magnetron co-sputtering at the extremely low temperature of 435°C. These thin films show a critical temperature of 16.3 K, a high critical current density of 1.60×10⁵A/cm², and a strong shielding effect. The key to achieving low-temperature growth is the independent kinetic control of Nb and Sn species in the sputtering process. From a technological viewpoint, the low-temperature approach paves the way for the use of Nb₃Sn as a coating in cryogenic efficient copper based cavities, thereby avoiding the detrimental interdiffusion of Cu