ACTA

Ultrathin NbN Films for Superconducting Single-Photon Detectors

W. Słysz^a, M. Guziewicz^a, M. Borysiewicz^a, J.Z. Domagała^b, I. Pasternak^a, K. Hejduk^a, W. Rzodkiewicz^a, J. Ratajczak^a, J. Bar^a, M. Węgrzecki^a, P. Grabiec^a, R. Grodecki^a, I. Węgrzecka^a and R. Sobolewski^{a, c}
^aInstitute of Electron Technology, al. Lotników 32/46, 02-668 Warsaw, Poland
^bInstitute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland
^cDepartments of Electrical and Computer Engineering and Physics and Astronomy, Materials Science Program, and Laboratory for Laser Energetics, University of Rochester, Rochester, NY-14627-0231, USA

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We present our research on fabrication and structural and transport characterization of ultrathin superconducting NbN layers deposited on both single-crystal Al₂O₃ and Si wafers, and SiO₂ and Si₃N₄ buffer layers grown directly on Si wafers. The thicknesses of our films varied from 6 nm to 50 nm and they were grown using reactive RF magnetron sputtering on substrates maintained at the temperature 850°C. We have performed extensive morphology characterization of our films using the X-ray diffraction method and atomic force microscopy, and related the results to the type of the substrate used for the film deposition. Our transport measurements showed that even the thinnest, 6 nm thick NbN films had the superconducting critical temperature of 10-12 K, which was increased to 14 K for thicker films.

DOI: 10.12693/APhysPolA.120.200
PACS numbers: 74.62.Bf, 74.78.-w, 81.15.Cd, 81.15.Jj