Mr. Sikdar earned his Ph.D. degree in Electronic Science from University of Calcutta, India in 2021. He held postdoctoral positions in the University of Sheffield, UK and IIT Bombay, India during 2022-2025. Currently, at NIMS, he is working on developing superconducting thin films for quantum circuit applications. His research expertise includes growth, characterization and fabrication of thin film/nanostructure-based devices for advanced electronic applications.

Presence of two-level defect states (TLSs) in the surface oxide layer is one of the major factors limiting the qubit coherence time in Al-based superconducting circuits. Ru could be a good alternative being less susceptible to form a native oxide layer.¹ However, its transition temperature (Tc) is significantly lower (~500 mK) than that of Al (~1.2 K) used in the current superconducting circuits. We report growth and characterization of Ru1-xRex alloy thin films on c-sapphire substrate by RF co-sputtering technique (Fig. 1(a)). It gradually increases Tc towards 2 K by incorporating Re into the alloy (Fig. 1(b)). Fig. 1(c) shows that the upper critical field of Ru0.22Re0.78 alloy surpluses its parent materials which could be due to the change in Fermi surface topology upon alloying.²

1. B. Langa Jr et al., APL Materials. 13, 061114 (2025) DOI: 10.1063/5.0271150.
2. C. W. Chu et al., Physical Review B. 3, 3757(1971) DOI: 10.1103/PhysRevB.3.3757.