Paper AS-ThP11
Structural, Morphological and Electrical Properties of Multilayer Sequentially Sputtered Nb₃Sn Films for Different Layer Thicknesses

Thursday, October 25, 2018, 6:00 pm, Room Hall B

Nb₃Sn is an intermetallic compound of A15 crystal structure that has type II superconductivity. Due to higher critical temperature T_c = 18.1 K and upper critical magnetic field of up to 30 T, Nb₃Sn is considered as an alternative of niobium for Superconducting Radio Frequency (SRF) applications in particle accelerators. Nb₃Sn coating on the inner surface of niobium SRF cavities can be operated at 4.2 K, whereas standard niobium cavities are currently operated at 2 K and consequently reduce the operation cost. However, synthesis of Nb₃Sn is challenging due to the availability of other phases of niobium and tin (Nb₆Sn₅ and NbSn₂), which have poor superconducting properties. We have fabricated Nb₃Sn films on sapphire using multilayer sequential sputtering. Several thin layers of Nb and Sn were deposited repeatedly by magnetron sputtering and annealed afterward at 950 °C for 3 hours to form Nb₃Sn. We have varied the Nb and Sn layer thicknesses of the films and characterized their crystal structure by X-ray diffraction (XRD), surface morphology by scanning electron microscopy (SEM), surface topography by atomic force microscopy (AFM), film stoichiometry by energy dispersive X-ray spectroscopy (EDS). The films showed crystalline structures of Nb₃Sn only. T_c up to 17.63 K with sharp superconducting transition has been achieved.