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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. |
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Title |
Electron energy relaxation in disordered superconducting NbN films |
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Journal Article |
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Year  |
2020 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
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Volume |
102 |
Issue |
5 |
Pages |
054501 (1 to 15) |
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Keywords |
NbN SSPD, SNSPD, HEB, bandwidth, relaxation time |
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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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2469-9950 |
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1266 |
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Tretyakov, I.; Svyatodukh, S.; Perepelitsa, A.; Ryabchun, S.; Kaurova, N.; Shurakov, A.; Smirnov, M.; Ovchinnikov, O.; Goltsman, G. |
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Title |
Ag2S QDs/Si heterostructure-based ultrasensitive SWIR range detector |
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Journal Article |
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Year |
2020 |
Publication |
Nanomaterials (Basel) |
Abbreviated Journal |
Nanomaterials (Basel) |
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10 |
Issue |
5 |
Pages |
1-12 |
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Keywords |
detector; quantum dots; short-wave infrared range; silicon |
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In the 20(th) century, microelectronics was revolutionized by silicon-its semiconducting properties finally made it possible to reduce the size of electronic components to a few nanometers. The ability to control the semiconducting properties of Si on the nanometer scale promises a breakthrough in the development of Si-based technologies. In this paper, we present the results of our experimental studies of the photovoltaic effect in Ag2S QD/Si heterostructures in the short-wave infrared range. At room temperature, the Ag2S/Si heterostructures offer a noise-equivalent power of 1.1 x 10(-10) W/ radicalHz. The spectral analysis of the photoresponse of the Ag2S/Si heterostructures has made it possible to identify two main mechanisms behind it: the absorption of IR radiation by defects in the crystalline structure of the Ag2S QDs or by quantum QD-induced surface states in Si. This study has demonstrated an effective and low-cost way to create a sensitive room temperature SWIR photodetector which would be compatible with the Si complementary metal oxide semiconductor technology. |
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Laboratory of nonlinear optics, Zavoisky Physical-Technical Institute of the Russian Academy of Sciences, Kazan 420029, Russia |
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2079-4991 |
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PMID:32365694; PMCID:PMC7712218 |
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1151 |
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Vodolazov, D. Y.; Manova, N. N.; Korneeva, Y. P.; Korneev, A. A. |
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Title |
Timing jitter in NbN superconducting microstrip single-photon detector |
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Journal Article |
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2020 |
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Phys. Rev. Applied |
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Phys. Rev. Applied |
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14 |
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4 |
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044041 (1 to 8) |
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Keywords |
NbN SSPD, SNSPD |
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We experimentally study timing jitter of single-photon detection by NbN superconducting strips with width w ranging from 190 nm to 3μm. We find that timing jitter of both narrow (190 nm) and micron-wide strips is about 40 ps at currents where internal detection efficiency η saturates and it is close to our instrumental jitter. We also calculate intrinsic timing jitter in wide strips using the modified time-dependent Ginzburg-Landau equation coupled with a two-temperature model. We find that with increasing width the intrinsic timing jitter increases and the effect is most considerable at currents where a rapid growth of η changes to saturation. We relate it with complicated vortex and antivortex dynamics, which depends on a photon’s absorption site across the strip and its width. The model also predicts that at current close to depairing current the intrinsic timing jitter of a wide strip could be about ℏ/kBTc (Tc is a critical temperature of superconductor), i.e., the same as for a narrow strip. |
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2331-7019 |
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1788 |
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Zhang, X.; Lita, A. E.; Smirnov, K.; Liu, H. L.; Zhu, D.; Verma, V. B.; Nam, S. W.; Schilling, A. |
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Title |
Strong suppression of the resistivity near the superconducting transition in narrow microbridges in external magnetic fields |
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Journal Article |
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Year |
2020 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
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Volume |
101 |
Issue |
6 |
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060508 (1 to 6) |
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MoSi, WSi films |
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We have investigated a series of superconducting bridges based on homogeneous amorphous WSi and MoSi films, with bridge widths w ranging from 2 to 1000μm and film thicknesses d∼4−6 and 100 nm. Upon decreasing the bridge widths below the respective Pearl lengths, we observe in all cases distinct changes in the characteristics of the resistive transitions to superconductivity. For each of the films, the resistivity curves R(B,T) separate at a well-defined and field-dependent temperature T∗(B) with decreasing the temperature, resulting in a dramatic suppression of the resistivity and a sharpening of the transitions with decreasing bridge width w. The associated excess conductivity in all the bridges scales as 1/w, which may suggest either the presence of a highly conducting region that is dominating the electric transport, or a change in the vortex dynamics in narrow enough bridges. We argue that this effect can only be observed in materials with sufficiently weak vortex pinning. |
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1800 |
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Zvagelsky, R. D.; Chubich, D. A.; Kolymagin, D. A.; Korostylev, E. V.; Kovalyuk, V. V.; Prokhodtsov, A. I.; Tarasov, A. V.; Goltsman, G. N.; Vitukhnovsky, A. G. |
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Title |
Three-dimensional polymer wire bonds on a chip: morphology and functionality |
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Journal Article |
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Year |
2020 |
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J. Phys. D: Appl. Phys. |
Abbreviated Journal |
J. Phys. D: Appl. Phys. |
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Volume |
53 |
Issue |
35 |
Pages |
355102 |
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photonic wire bonds, PWB |
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Modern microchip-scale transceivers are capable of transmitting data at rates of the order of several terabits per second. In this regard, there is an urgent need to improve the interfaces connecting the chips and extend the bandpass of the interconnections. We use an approach combining silicon nitride nanophotonic circuits with 3D polymer waveguides fabricated by direct laser writing, which can be used as photonic interconnections or photonic wire bonds (PWB). These structures are designed, simulated, fabricated, and optimized for better light transmission at the telecommunication wavelength. An important part of this work is the study of the telecom signal transmission in a 3D polymer waveguide connecting two silicon nitride facing tapers. Two cases are considered: the tapers are one opposite the other or misaligned. Initially, the PWB shape was chosen to be Gaussian and then optimized: the top was circle-shaped and with the lower part still being Gaussian. Transmission losses were measured for both types of waveguides with different shapes. The idea of an optical multi-level crossing for photonic integrated circuits is also suggested as a solution to the problem of interconnections within a single chip. |
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0022-3727 |
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1181 |
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