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Voronov BM, Gershenzon EM, Gol'tsman GN, Gubkina TO, Semash VD. Superconductive properties of ultrathin NbN films on different substrates. Sverkhprovodimost': Fizika, Khimiya, Tekhnika. 1994;7(6):1097–102.
Abstract: A study was made on dependence of surface resistance, critical temperature and width of superconducting transition on application temperature and thickness of NbN films, which varied within the range of 3-10 nm. Plates of sapphire, fused and monocrystalline quartz, MgO, as well as Si and silicon oxide were used as substrates. NbN films with 160 μθ·cm specific resistance and 16.5 K (Tc) critical temperature were obtained on sapphire substrates. Intensive growth of ΔTc was noted for films, applied on fused quartz, with increase of precipitation temperature. This is explained by occurrence of high tensile stresses in NbN films, caused by sufficient difference of thermal coefficients of expansion of NbN and quartz.
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Korneev A, Minaeva O, Rubtsova I, Milostnaya I, Chulkova G, Voronov B, et al. Superconducting single-photon ultrathin NbN film detector. Quantum Electronics. 2005;35(8):698–700.
Abstract: Superconducting single-photon ultrathin NbN film detectors are studied. The development of manufacturing technology of detectors and the reduction of their operating temperature down to 2 K resulted in a considerable increase in their quantum efficiency, which reached in the visible region (at 0.56 μm) 30%—40%, i.e., achieved the limit determined by the absorption coefficient of the film. The quantum efficiency exponentially decreases with increasing wavelength, being equal to ~20% at 1.55 μm and ~0.02% at 5 μm. For the dark count rate of ~10-4s-1, the experimental equivalent noise power was 1.5×10-20 W Hz-1/2; it can be decreased in the future down to the record low value of 5×10-21 W Hz-1/2. The time resolution of the detector is 30 ps.
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Gershenzon EM, Gol'tsman GN, Semenov AD. Submillimeter backward wave tube spectrometer for measuring superconducting film transmission. Pribory i Tekhnika Eksperimenta. 1983;26(5):134–7.
Abstract: A spectrometer employing six backward wave tubes is described. It is intended for investigation of superconductors in the 0.2-3 mm range of wave lengths. During the measurement of the transmission spectrum it is possible to determine the energy gap for superconduct1ng films 50 to 4000 A thick. The transmission factor can vary from 10-1 to 10-9. Spectrum of relation of film transmission factors in superconducting and normal states is measured for determining the energy gap 2 Δ. The transmission spectrum obtained by means of a computer for vanadium film 300 A thick is given as an example. The energy gap 2 Δ = 1.4 MeV
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