2025/12/19 by Francesca Incalza, Matteo Castellani, Incalza, Francesca +13
Materials Science · Physics and Astronomy · #Applied Physics (physics.app-ph) #Diamond and Carbon-based Materials Research #FOS: Physical sciences #Physics of Superconductivity and Magnetism #Superconducting and THz Device Technology
paper · doi:10.48550/arxiv.2512.18063
openalex publication_date 2025/12/19 · openalex created_date 2025/12/24 · openalex updated_date 2026/07/28
Achieving both high internal efficiency and fast reset times at elevated temperatures remains challenging due to limited understanding of how film properties govern SNSPD performance. We demonstrate that epitaxial NbN films on sapphire enable simultaneous high efficiency and rapid response. We fabricate and characterize SNSPDs based on these films deposited via DC magnetron sputtering on c-cut sapphire. High-quality epitaxial growth preserves a low electron diffusion coefficient and promotes strong electron-phonon coupling, yielding a high critical temperature and efficient hotspot formation in the dirty limit. X-ray diffraction and transmission electron microscopy confirm epitaxial alignment and lattice order. Nanowires of 20 nm width exhibit saturated internal efficiency at 1550 nm wavelength and short reset times at 4.2 K, enabled by lattice matching and high thermal conductance of the sapphire interface. Ab initio modeling reproduces photon count rates, linking device performance quantitatively to film properties such as diffusivity and electron-phonon coupling.