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Author Tret'yakov, I. V.; Kaurova, N. S.; Voronov, B. M.; Anfert'ev, V. A.; Revin, L. S.; Vaks, V. L.; Gol'tsman, G. N. doi  openurl
  Title The influence of the diffusion cooling on the noise band of the superconductor NbN hot-electron bolometer operating in the terahertz range Type Journal Article
  Year 2016 Publication Tech. Phys. Lett. Abbreviated Journal  
  Volume (down) 42 Issue 6 Pages 563-566  
  Keywords HEB, noise bandwidth, conversion gain bandwidth, noise temperature, Andreev reflection  
  Abstract Results of an experimental study of the noise temperature (Tn) and noise bandwidth (NBW) of the superconductor NbN hot-electron bolometer (HEB) mixer as a function of its temperature (Tb) are presented. It was determined that the NBW of the mixer is significantly wider at temperatures close to the critical ones (Tc) than are values measured at 4.2 K. The NBW of the mixer measured at the heterodyne frequency of 2.5 THz at temperature Tb close to Tc was ~13 GHz, as compared with 6 GHz at Tb = 4.2 K. This experiment clearly demonstrates the limitation of the thermal flow from the NbN bridge at Tb â‰<aa> Tc for mixers manufactured by the in situ technique. This limitation is close in its nature to the Andreev reflection on the superconductor/ metal boundary. In this case, the noise temperature of the studied mixer increased from 1100 to 3800 K.  
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  Notes Approved no  
  Call Number Serial 1106  
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Author Beebe, M. R.; Beringer, D. B.; Burton, M. C.; Yang, K.; Lukaszew, R. A. url  doi
openurl 
  Title Stoichiometry and thickness dependence of superconducting properties of niobium nitride thin films Type Journal Article
  Year 2016 Publication Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films Abbreviated Journal Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films  
  Volume (down) 34 Issue 2 Pages 021510 (1 to 4)  
  Keywords potential plagiarism, possible plagiarism, NbN films  
  Abstract The current technology used in linear particle accelerators is based on superconducting radio frequency (SRF) cavities fabricated from bulk niobium (Nb), which have smaller surface resistance and therefore dissipate less energy than traditional nonsuperconducting copper cavities. Using bulk Nb for the cavities has several advantages, which are discussed elsewhere; however, such SRF cavities have a material-dependent accelerating gradient limit. In order to overcome this fundamental limit, a multilayered coating has been proposed using layers of insulating and superconducting material applied to the interior surface of the cavity. The key to this multilayered model is to use superconducting thin films to exploit the potential field enhancement when these films are thinner than their London penetration depth. Such field enhancement has been demonstrated in MgB2 thin films; here, the authors consider films of another type-II superconductor, niobium nitride (NbN). The authors present their work correlating stoichiometry and superconducting properties in NbN thin films and discuss the thickness dependence of their superconducting properties, which is important for their potential use in the proposed multilayer structure. While there are some previous studies on the relationship between stoichiometry and critical temperature TC, the authors are the first to report on the correlation between stoichiometry and the lower critical field HC1.  
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  Series Volume Series Issue Edition  
  ISSN 0734-2101 ISBN Medium  
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  Notes Potential plagiarism for 1503 Approved no  
  Call Number Serial 1504  
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Author Arutyunov, K. Y.; Ramos-Alvarez, A.; Semenov, A. V.; Korneeva, Y. P.; An, P. P.; Korneev, A. A.; Murphy, A.; Bezryadin, A.; Gol'tsman, G. N. url  doi
openurl 
  Title Superconductivity in highly disordered NbN nanowires Type Journal Article
  Year 2016 Publication Nanotechnol. Abbreviated Journal Nanotechnol.  
  Volume (down) 27 Issue 47 Pages 47lt02 (1 to 8)  
  Keywords NbN nanowires  
  Abstract The topic of superconductivity in strongly disordered materials has attracted significant attention. These materials appear to be rather promising for fabrication of various nanoscale devices such as bolometers and transition edge sensors of electromagnetic radiation. The vividly debated subject of intrinsic spatial inhomogeneity responsible for the non-Bardeen-Cooper-Schrieffer relation between the superconducting gap and the pairing potential is crucial both for understanding the fundamental issues of superconductivity in highly disordered superconductors, and for the operation of corresponding nanoelectronic devices. Here we report an experimental study of the electron transport properties of narrow NbN nanowires with effective cross sections of the order of the debated inhomogeneity scales. The temperature dependence of the critical current follows the textbook Ginzburg-Landau prediction for the quasi-one-dimensional superconducting channel I c approximately (1-T/T c)(3/2). We find that conventional models based on the the phase slip mechanism provide reasonable fits for the shape of R(T) transitions. Better agreement with R(T) data can be achieved assuming the existence of short 'weak links' with slightly reduced local critical temperature T c. Hence, one may conclude that an 'exotic' intrinsic electronic inhomogeneity either does not exist in our structures, or, if it does exist, it does not affect their resistive state properties, or does not provide any specific impact distinguishable from conventional weak links.  
  Address National Research University Higher School of Economics, Moscow Institute of Electronics and Mathematics,109028, Moscow, Russia. P L Kapitza Institute for Physical Problems RAS, Moscow, 119334, Russia  
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  Series Volume Series Issue Edition  
  ISSN 0957-4484 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:27782000 Approved no  
  Call Number Serial 1332  
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Author Korneeva, Y.; Sidorova, M.; Semenov, A.; Krasnosvobodtsev, S.; Mitsen, K.; Korneev, A.; Chulkova, G.; Goltsman, G. url  doi
openurl 
  Title Comparison of hot-spot formation in NbC and NbN single-photon detectors Type Journal Article
  Year 2016 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.  
  Volume (down) 26 Issue 3 Pages 1-4  
  Keywords NbC, NbN SSPD, SNSPD  
  Abstract We report an experimental investigation of the hot-spot evolution in superconducting single-photon detectors made of disordered superconducting materials with different diffusivity and energy downconversion time values, i.e., 33-nm-thick NbN and 23-nm-thick NbC films. We have demonstrated that, in NbC film, only 405-nm photons produce sufficiently large hot spot to trigger a single-photon response. The dependence of detection efficiency on bias current for 405-nm photons in NbC is similar to that for 3400-nm photons in NbN. In NbC, large diffusivity and downconversion time result in 1-D critical current suppression profile compared with the usual 2-D profile in NbN.  
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  Series Volume Series Issue Edition  
  ISSN 1051-8223 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 1348  
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Author Shcherbatenko, M.; Lobanov, Y.; Semenov, A.; Kovalyuk, V.; Korneev, A.; Ozhegov, R.; Kazakov, A.; Voronov, B.M.; Goltsman, G.N. url  doi
openurl 
  Title Potential of a superconducting photon counter for heterodyne detection at the telecommunication wavelength Type Journal Article
  Year 2016 Publication Opt. Express Abbreviated Journal Opt. Express  
  Volume (down) 24 Issue 26 Pages 30474-30484  
  Keywords NbN SSPD mixer, SNSPD  
  Abstract Here, we report on the successful operation of a NbN thin film superconducting nanowire single-photon detector (SNSPD) in a coherent mode (as a mixer) at the telecommunication wavelength of 1550 nm. Providing the local oscillator power of the order of a few picowatts, we were practically able to reach the quantum noise limited sensitivity. The intermediate frequency gain bandwidth (also referred to as response or conversion bandwidth) was limited by the spectral band of a single-photon response pulse of the detector, which is proportional to the detector size. We observed a gain bandwidth of 65 MHz and 140 MHz for 7 x 7 microm2 and 3 x 3 microm2 devices, respectively. A tiny amount of the required local oscillator power and wide gain and noise bandwidths, along with unnecessary low noise amplification, make this technology prominent for various applications, with the possibility for future development of a photon counting heterodyne-born large-scale array.  
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  Series Volume Series Issue Edition  
  ISSN 1094-4087 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:28059394 Approved no  
  Call Number Serial 1207  
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