• Progress in Superconductivity and Cryogenics
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• v.23 no.4
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• pp.1-5
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• 2021

Among elemental metals, niobium (Nb) has the highest superconducting transition temperature (T_c) at ambient pressure. Thus, Nb films have been used in superconducting electronics and radio frequency cavity applications. In this study, the depositional factors determining the crystallinity and T_c of Nb films were investigated. An Nb film grown at a sputtering temperature of 240℃ exhibited the maximum crystallinity of Nb and the minimum crystallinity of niobium oxide. X-ray photoelectron spectroscopy confirmed a maximum atomic percent of niobium and a minimum atomic percent of oxygen. A sputtering power of 210 W and a sputtering time of 50 min were the optimal conditions for Nb deposition, and the T_c of the optimized film (9.08 K) was close to that of bulk Nb (9.25 K). Transmission electron microscopy images of the thick film directly confirmed the removal of the typical in-plane compressive strain in the (110) plane caused by residual stress.