Ultrathin NbN Films for Superconducting Single-Photon Detectors
W. Słysza, M. Guziewicza, M. Borysiewicza, J.Z. Domagałab, I. Pasternaka, K. Hejduka, W. Rzodkiewicza, J. Ratajczaka, J. Bara, M. Węgrzeckia, P. Grabieca, R. Grodeckia, I. Węgrzeckaa and R. Sobolewskia, 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