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Author Zolotov, P.; Semenov, A.; Divochiy, A.; Goltsman, G. url  doi
openurl 
  Title A comparison of VN and NbN thin films towards optimal SNSPD efficiency Type Journal Article
  Year 2021 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.  
  Volume 31 Issue 5 Pages 1-4  
  Keywords NbN SSPD, SNSPD, WSi  
  Abstract Based on early phenomenological ideas about the operation of superconducting single-photon detectors (SSPD or SNSPD), it was expected that materials with a lower superconducting gap should perform better in the IR range. The plausibility of this concept could be checked using two popular SSPD materials – NbN and WSi films. However, these materials differ strongly in crystallographic structure (polycrystalline B1 versus amorphous), which makes their dependence on disorder different. In our work we present a study of the single-photon response of SSPDs made from two disordered B1 structure superconductors – vanadium nitride and niobium nitride thin films. We compare the intrinsic efficiency of devices made from films with different sheet resistance values. While both materials have a polycrystalline structure and comparable diffusion coefficient values, VN films show metallic behavior over a wide range of sheet resistance, in contrast to NbN films with an insulator-like temperature dependence of resistivity, which may be partially due to enhanced Coulomb interaction, leading to different starting points for the normal electron density of states. The results show that even though VN devices are more promising in terms of theoretical predictions, their optimal performance was not reached due to lower values of sheet resistance.  
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1051-8223 ISBN Medium  
  Area Expedition Conference (up)  
  Notes Approved no  
  Call Number Serial 1223  
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Author Baeva, E. M.; Sidorova, M. V.; Korneev, A. A.; Smirnov, K. V.; Divochy, A. V.; Morozov, P. V.; Zolotov, P. I.; Vakhtomin, Y. B.; Semenov, A. V.; Klapwijk, T. M.; Khrapai, V. S.; Goltsman, G. N. url  doi
openurl 
  Title Thermal properties of NbN single-photon detectors Type Journal Article
  Year 2018 Publication Phys. Rev. Applied Abbreviated Journal Phys. Rev. Applied  
  Volume 10 Issue 6 Pages 064063 (1 to 8)  
  Keywords NbN SSPD, SNSPD  
  Abstract We investigate thermal properties of a NbN single-photon detector capable of unit internal detection efficiency. Using an independent calibration of the coupling losses, we determine the absolute optical power absorbed by the NbN film and, via resistive superconductor thermometry, the temperature dependence of the thermal resistance Z(T) of the NbN film. In principle, this approach permits simultaneous measurement of the electron-phonon and phonon-escape contributions to the energy relaxation, which in our case is ambiguous because of the similar temperature dependencies. We analyze Z(T) with a two-temperature model and impose an upper bound on the ratio of electron and phonon heat capacities in NbN, which is surprisingly close to a recent theoretical lower bound for the same quantity in similar devices.  
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  Series Editor Series Title Abbreviated Series Title  
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  ISSN 2331-7019 ISBN Medium  
  Area Expedition Conference (up)  
  Notes Approved no  
  Call Number Serial 1226  
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Author Smirnov, K.; Divochiy, A.; Vakhtomin, Y.; Morozov, P.; Zolotov, P.; Antipov, A.; Seleznev, V. url  doi
openurl 
  Title NbN single-photon detectors with saturated dependence of quantum efficiency Type Journal Article
  Year 2018 Publication Supercond. Sci. Technol. Abbreviated Journal Supercond. Sci. Technol.  
  Volume 31 Issue 3 Pages 035011 (1 to 8)  
  Keywords NbN SSPD, SNSPD  
  Abstract The possibility of creating NbN superconducting single-photon detectors with saturated dependence of quantum efficiency (QE) versus normalized bias current was investigated. It was shown that the saturation increases for the detectors based on finer films with a lower value of Rs300/Rs20. The decreasing of Rs300/Rs20 was related to the increasing influence of quantum corrections to conductivity of superconductors and, in turn, to the decrease of the electron diffusion coefficient. The best samples have a constant value of system QE 94% at Ib/Ic ~ 0.8 and wavelength 1310 nm.  
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0953-2048 ISBN Medium  
  Area Expedition Conference (up)  
  Notes Approved no  
  Call Number Serial 1232  
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Author Zolotov, P. I.; Divochiy, A. V.; Vakhtomin, Y. B.; Morozov, P. V.; Seleznev, V. A.; Smirnov, K. V. url  doi
openurl 
  Title Development of high-effective superconducting single-photon detectors aimed for mid-IR spectrum range Type Conference Article
  Year 2017 Publication J. Phys.: Conf. Ser. Abbreviated Journal J. Phys.: Conf. Ser.  
  Volume 917 Issue Pages 062037  
  Keywords NbN SSPD, SNSPD  
  Abstract We report on development of superconducting single-photon detectors (SSPD) with high intrinsic quantum efficiency in the wavelength range 1.31 – 3.3 μm. By optimization of the NbN film thickness and its compound, we managed to improve detection efficiency of the detectors in the range up to 3.3 μm. Optimized devices showed intrinsic quantum efficiencies as high as 10% at mid-IR range.  
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1742-6588 ISBN Medium  
  Area Expedition Conference (up)  
  Notes Approved no  
  Call Number Serial 1233  
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Author Sidorova, M.; Semenov, Alexej D.; Hübers, H.-W.; Ilin, K.; Siegel, M.; Charaev, I.; Moshkova, M.; Kaurova, N.; Goltsman, G. N.; Zhang, X.; Schilling, A. url  doi
openurl 
  Title Electron energy relaxation in disordered superconducting NbN films Type Journal Article
  Year 2020 Publication Phys. Rev. B Abbreviated Journal Phys. Rev. B  
  Volume 102 Issue 5 Pages 054501 (1 to 15)  
  Keywords NbN SSPD, SNSPD, HEB, bandwidth, relaxation time  
  Abstract We report on the inelastic-scattering rate of electrons on phonons and relaxation of electron energy studied by means of magnetoconductance, and photoresponse, respectively, in a series of strongly disordered superconducting NbN films. The studied films with thicknesses in the range from 3 to 33 nm are characterized by different Ioffe-Regel parameters but an almost constant product qTl (qT is the wave vector of thermal phonons and l is the elastic mean free path of electrons). In the temperature range 14–30 K, the electron-phonon scattering rates obey temperature dependencies close to the power law 1/τe−ph∼Tn with the exponents n≈3.2–3.8. We found that in this temperature range τe−ph and n of studied films vary weakly with the thickness and square resistance. At 10 K electron-phonon scattering times are in the range 11.9–17.5 ps. The data extracted from magnetoconductance measurements were used to describe the experimental photoresponse with the two-temperature model. For thick films, the photoresponse is reasonably well described without fitting parameters, however, for thinner films, the fit requires a smaller heat capacity of phonons. We attribute this finding to the reduced density of phonon states in thin films at low temperatures. We also show that the estimated Debye temperature in the studied NbN films is noticeably smaller than in bulk material.  
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 2469-9950 ISBN Medium  
  Area Expedition Conference (up)  
  Notes Approved no  
  Call Number Serial 1266  
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