Progress in Superconductivity and Cryogenics (한국초전도ㆍ저온공학회논문지)

The Korean Society of Superconductivity and Cryogenics (한국초전도저온학회)
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Dependence of superconductivity on the crystallinity of Nb films on Si wafers

  • Received : 2021.12.18
  • Accepted : 2021.12.30
  • Published : 2021.12.31
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Abstract

Among elemental metals, niobium (Nb) has the highest superconducting transition temperature (Tc) 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 Tc 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 Tc 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.

Keywords

Acknowledgement

This work was funded by the National Research Foundation of Korea (NRF), Nos. NRF-2019R1A2C1089017 and NRF-2019R1I1A1A01061738; and the Ministry of SMEs and Startups (MSS, Korea), No. S2912700.

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