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Smirnov, K.; Divochiy, A.; Vakhtomin, Y.; Morozov, P.; Zolotov, P.; Antipov, A.; Seleznev, V. |
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Title |
NbN single-photon detectors with saturated dependence of quantum efficiency |
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Journal Article |
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Year |
2018 |
Publication |
Supercond. Sci. Technol. |
Abbreviated Journal |
Supercond. Sci. Technol. |
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31 |
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3 |
Pages |
035011 (1 to 8) |
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Keywords |
NbN SSPD, SNSPD |
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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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0953-2048 |
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1232 |
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Zolotov, P. I.; Semenov, A. V.; Divochiy, A. V.; Goltsman, G. N.; Romanov, N. R.; Klapwijk, T. M. |
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Title |
Dependence of photon detection efficiency on normal-state sheet resistance in marginally superconducting films of NbN |
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Journal Article |
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Year |
2021 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
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31 |
Issue |
5 |
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1-5 |
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Keywords |
NbN SSPD, SNSPD |
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We present an extensive set of data on nanowire-type superconducting single-photon detectors based on niobium-nitride (NbN) to establish the empirical correlation between performance and the normal-state resistance per square. We focus, in particular, on the bias current, compared to the expected depairing current, needed to achieve a near-unity detection efficiency for photon detection. The data are discussed within the context of a model in which the photon energy triggers the movement of vortices i.e. superconducting dissipation, followed by thermal runaway. Since the model is based on the non-equilibrium theory for conventional superconductors deviations may occur, because the efficient regime is found when NbN acts as a marginal superconductor in which long-range phase coherence is frustrated. |
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1051-8223 |
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1222 |
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Zolotov, P.; Semenov, A.; Divochiy, A.; Goltsman, G. |
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A comparison of VN and NbN thin films towards optimal SNSPD efficiency |
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Journal Article |
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2021 |
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IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
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31 |
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5 |
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1-4 |
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Keywords |
NbN SSPD, SNSPD, WSi |
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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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1051-8223 |
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1223 |
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Samsonova, A. S.; Zolotov, P. I.; Baeva, E. M.; Lomakin, A. I.; Titova, N. A.; Kardakova, A. I.; Goltsman, G. N. |
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Title |
Signatures of surface magnetic disorder in niobium films |
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Journal Article |
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Year |
2021 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
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31 |
Issue |
5 |
Pages |
1-5 |
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Keywords |
Nb films |
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We present our studies on the evolution of the normal and superconducting properties with thickness of thin Nb films with a low level of non-magnetic disorder ( kFl≈150 for the thickest film in the set). The analysis of the superconducting behavior points to the presence of magnetic moments, hidden in the native oxide on the surface of Nb films. Using the Abrikosov-Gorkov theory, we obtain the density of surface magnetic moments of 1013 cm −2 , which is in agreement with the previously reported data for Nb films. |
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1051-8223 |
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1792 |
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Seleznev, V. A.; Divochiy, A. V.; Vakhtomin, Y. B.; Morozov, P. V.; Zolotov, P. I.; Vasil'ev, D. D.; Moiseev, K. M.; Malevannaya, E. I.; Smirnov, K. V. |
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Title |
Superconducting detector of IR single-photons based on thin WSi films |
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Conference Article |
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Year |
2016 |
Publication |
J. Phys.: Conf. Ser. |
Abbreviated Journal |
J. Phys.: Conf. Ser. |
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Volume |
737 |
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012032 |
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Keywords |
WSi SSPD, SNSPD, NEP |
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We have developed the deposition technology of WSi thin films 4 to 9 nm thick with high temperature values of superconducting transition (Tc~4 K). Based on deposed films there were produced nanostructures with indicative planar sizes ~100 nm, and the research revealed that even on nanoscale the films possess of high critical temperature values of the superconducting transition (Tc~3.3-3.7 K) which certifies high quality and homogeneity of the films created. The first experiments on creating superconducting single-photon detectors showed that the detectors' SDE (system detection efficiency) with increasing bias current (I b) reaches a constant value of ~30% (for X=1.55 micron) defined by infrared radiation absorption by the superconducting structure. To enhance radiation absorption by the superconductor there were created detectors with cavity structures which demonstrated a practically constant value of quantum efficiency >65% for bias currents Ib>0.6-Ic. The minimal dark counts level (DC) made 1 s-1 limited with background noise. Hence WSi is the most promising material for creating single-photon detectors with record SDE/DC ratio and noise equivalent power (NEP). |
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1742-6588 |
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1235 |
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