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Author |
Shurakov, A.; Seliverstov, S.; Kaurova, N.; Finkel, M.; Voronov, B.; Goltsman, G. |
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Title |
Input bandwidth of hot electron bolometer with spiral antenna |
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Journal Article |
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Year |
2012 |
Publication |
IEEE Trans. THz Sci. Technol. |
Abbreviated Journal |
IEEE Trans. THz Sci. Technol. |
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2 |
Issue |
4 |
Pages |
400-405 |
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Keywords |
NbN HEB bolometers bandwidth, log-spiral antenna |
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Abstract |
We report the results of our study of the input bandwidth of hot electron bolometers (HEB) embedded into the planar log-spiral antenna. The sensitive element is made of the ultrathin superconducting NbN film patterned as a bridge at the feed of the antenna. The contacts between the antenna and a sensitive element are made from in situ deposited gold (i.e., deposited over NbN film without breaking vacuum), which gives high quality contacts and makes the response of the HEB at higher frequencies less affected by the RF loss. An accurate experimental spectroscopic procedure is demonstrated that leads to the confirmation of the wide ( 8 THz) bandwidth in this antenna coupled device. |
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2156-342X |
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1161 |
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Author |
Samsonova, Alena; Zolotov, Philipp; Baeva, Elmira; Lomakin, Andrey; Titova, Nadezhda; Kardakova, Anna; Goltsman, Gregory |
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Title |
Signatures of surface magnetic disorder in thin niobium films |
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Journal Article |
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Year |
2021 |
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IEEE Trans. Appl. Supercond. |
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1-1 |
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Temperature measurement, Temperature dependence, Superconducting magnets, Superconducting transition temperature, Substrates, Resistance, Scattering |
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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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1162 |
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Baeva, E. M.; Titova, N. A.; Veyrat, L.; Sacépé, B.; Semenov, A. V.; Goltsman, G. N.; Kardakova, A. I.; Khrapai, V. S. |
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Title |
Thermal relaxation in metal films bottlenecked by diffuson lattice excitations of amorphous substrates |
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Miscellaneous |
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2021 |
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arXiv |
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arXiv |
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metal films, NbN, InOx, Au/Ni, thermal relaxation |
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Here we examine the role of the amorphous insulating substrate in the thermal relaxation in thin NbN, InOx, and Au/Ni films at temperatures above 5 K. The studied samples are made up of metal bridges on an amorphous insulating layer lying on or suspended above a crystalline substrate. Noise thermometry was used to measure the electron temperature Te of the films as a function of Joule power per unit of area P2D. In all samples, we observe the dependence P2D∝Tne with the exponent n≃2, which is inconsistent with both electron-phonon coupling and Kapitza thermal resistance. In suspended samples, the functional dependence of P2D(Te) on the length of the amorphous insulating layer is consistent with the linear T-dependence of the thermal conductivity, which is related to lattice excitations (diffusons) for the phonon mean free path smaller than the dominant phonon wavelength. Our findings are important for understanding the operation of devices embedded in amorphous dielectrics. |
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1163 |
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Author |
Baeva, E. M.; Titova, N. A.; Kardakova, A. I.; Piatrusha, S. U.; Khrapai, V. S. |
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Title |
Universal bottleneck for thermal relaxation in disordered metallic films |
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Journal Article |
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Year |
2020 |
Publication |
JETP Lett. |
Abbreviated Journal |
Jetp Lett. |
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Volume |
111 |
Issue |
2 |
Pages |
104-108 |
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Keywords |
NbN disordered metallic films, thermal relaxation |
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We study the heat relaxation in current biased metallic films in the regime of strong electron–phonon coupling. A thermal gradient in the direction normal to the film is predicted, with a spatial temperature profile determined by the temperature-dependent heat conduction. In the case of strong phonon scattering, the heat conduction occurs predominantly via the electronic system and the profile is parabolic. This regime leads to the linear dependence of the noise temperature as a function of bias voltage, in spite of the fact that all the dimensions of the film are large compared to the electron–phonon relaxation length. This is in stark contrast to the conventional scenario of relaxation limited by the electron–phonon scattering rate. A preliminary experimental study of a 200-nm-thick NbN film indicates the relevance of our model for materials used in superconducting nanowire single-photon detectors. |
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0021-3640 |
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1164 |
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Titova, N. A.; Baeva, E. M.; Kardakova, A. I.; Goltsman, G. N. |
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Title |
Fabrication of NbN/SiNx:H/SiO2 membrane structures for study of heat conduction at low temperatures |
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Conference Article |
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Year |
2020 |
Publication |
J. Phys.: Conf. Ser. |
Abbreviated Journal |
J. Phys.: Conf. Ser. |
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1695 |
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012190 |
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NbN films, insulating membrane |
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Here we report on the development of NbN/SiNx:H/SiO2-membrane structures for investigation of the thermal transport at low temperatures. Thin NbN films are known to be in the regime of a strong electron-phonon coupling, and one can assume that the phononic and electronic baths in the NbN are in local equilibrium. In such case, the cooling of the NbN-based devices strongly depends on acoustic matching to the substrate and substrate thermal characteristics. For the insulating membrane much thicker than the NbN film, our preliminary results demonstrate that the membrane serves as an additional channel for the thermal relaxation of the NbN sample. That implies a negligible role of thermal boundary resistance of the NbN-SiNx:H interface in comparison with the internal thermal resistance of the insulating membrane. |
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1742-6588 |
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1165 |
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Saveskul, N. A.; Titova, N. A.; Baeva, E. M.; Semenov, A. V.; Lubenchenko, A. V.; Saha, S.; Reddy, H.; Bogdanov, S. I.; Marinero, E. E.; Shalaev, V. M.; Boltasseva, A.; Khrapai, V. S.; Kardakova, A. I.; Goltsman, G. N. |
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Title |
Superconductivity behavior in epitaxial TiN films points to surface magnetic disorder |
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Journal Article |
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Year |
2019 |
Publication |
Phys. Rev. Applied |
Abbreviated Journal |
Phys. Rev. Applied |
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12 |
Issue |
5 |
Pages |
054001 |
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epitaxial TiN films |
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We analyze the evolution of the normal and superconducting properties of epitaxial TiN films, characterized by high Ioffe-Regel parameter values, as a function of the film thickness. As the film thickness decreases, we observe an increase of the residual resistivity, that becomes dominated by diffusive surface scattering for d≤20nm. At the same time, a substantial thickness-dependent reduction of the superconducting critical temperature is observed compared to the bulk TiN value. In such high-quality material films, this effect can be explained by a weak magnetic disorder residing in the surface layer with a characteristic magnetic defect density of approximately 1012cm−2. Our results suggest that surface magnetic disorder is generally present in oxidized TiN films. |
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2331-7019 |
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1166 |
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Kardakova, A.; Shishkin, A.; Semenov, A.; Goltsman, G. N.; Ryabchun, S.; Klapwijk, T. M.; Bousquet, J.; Eon, D.; Sacépé, B.; Klein, T.; Bustarret, E. |
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Relaxation of the resistive superconducting state in boron-doped diamond films |
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Journal Article |
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2016 |
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Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
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93 |
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6 |
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064506 |
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boron-doped diamond films, resistive superconducting state, relaxation time |
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We report a study of the relaxation time of the restoration of the resistive superconducting state in single crystalline boron-doped diamond using amplitude-modulated absorption of (sub-)THz radiation (AMAR). The films grown on an insulating diamond substrate have a low carrier density of about 2.5×1021cm−3 and a critical temperature of about 2K. By changing the modulation frequency we find a high-frequency rolloff which we associate with the characteristic time of energy relaxation between the electron and the phonon systems or the relaxation time for nonequilibrium superconductivity. Our main result is that the electron-phonon scattering time varies clearly as T−2, over the accessible temperature range of 1.7 to 2.2 K. In addition, we find, upon approaching the critical temperature Tc, evidence for an increasing relaxation time on both sides of Tc. |
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2469-9950 |
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1167 |
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Titova, N.; Kardakova, A. I.; Tovpeko, N.; Ryabchun, S.; Mandal, S.; Morozov, D.; Klemencic, G. M.; Giblin, S. R.; Williams, O. A.; Goltsman, G. N.; Klapwijk, T. M. |
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Slow electron–phonon cooling in superconducting diamond films |
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Journal Article |
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2017 |
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IEEE Trans. Appl. Supercond. |
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IEEE Trans. Appl. Supercond. |
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27 |
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4 |
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1-4 |
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superconducting diamond films, electron-phonon cooling |
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We have measured the electron-phonon energy-relaxation time, τ eph , in superconducting boron-doped diamond films grown on silicon substrate by chemical vapor deposition. The observed electron-phonon cooling times vary from 160 ns at 2.70 K to 410 ns at 1.8 K following a T -2-dependence. The data are consistent with the values of τ eph previously reported for single-crystal boron-doped diamond films epitaxially grown on diamond substrate. Such a noticeable slow electron-phonon relaxation in boron-doped diamond, in combination with a high normal-state resistivity, confirms a potential of superconducting diamond for ultrasensitive superconducting bolometers. |
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1051-8223 |
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1168 |
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Gayduchenko, I.; Kardakova, A.; Fedorov, G.; Voronov, B.; Finkel, M.; Jiménez, D.; Morozov, S.; Presniakov, M.; Goltsman, G. |
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Title |
Response of asymmetric carbon nanotube network devices to sub-terahertz and terahertz radiation |
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Journal Article |
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2015 |
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J. Appl. Phys. |
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J. Appl. Phys. |
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118 |
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19 |
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194303 |
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terahertz detectors, asymmetric carbon nanotubes, CNT |
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Demand for efficient terahertz radiation detectors resulted in intensive study of the asymmetric carbon nanostructures as a possible solution for that problem. It was maintained that photothermoelectric effect under certain conditions results in strong response of such devices to terahertz radiation even at room temperature. In this work, we investigate different mechanisms underlying the response of asymmetric carbon nanotube (CNT) based devices to sub-terahertz and terahertz radiation. Our structures are formed with CNT networks instead of individual CNTs so that effects probed are more generic and not caused by peculiarities of an individual nanoscale object. We conclude that the DC voltage response observed in our structures is not only thermal in origin. So called diode-type response caused by asymmetry of the device IV characteristic turns out to be dominant at room temperature. Quantitative analysis provides further routes for the optimization of the device configuration, which may result in appearance of novel terahertz radiation detectors. |
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0021-8979 |
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1169 |
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Tretyakov, I. V.; Finkel, M. I.; Ryabchun, S. A.; Kardakova, A. I.; Seliverstov, S. V.; Petrenko, D. V.; Goltsman, G. N. |
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Title |
Hot-electron bolometer mixers with in situ contacts |
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Journal Article |
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2014 |
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Radiophys. Quant. Electron. |
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Radiophys. Quant. Electron. |
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56 |
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8-9 |
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591-598 |
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HEB mixers |
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We report on the latest achievements in the development of superconducting hot-electron bolometer (HEB) mixers for terahertz superheterodyne receivers. We consider application ranges of such receivers and requirements for the basic characteristics of the mixers. Main features of the mixers, such as noise temperature, gain bandwidth, noise bandwidth, and required local-oscillator power, have been improved significantly over the past few years due to intense research work, both in terms of the element fabrication quality and in terms of understanding of the physics of the processes occurring in the HEB mixers. Contacts between the superconducting bridge and the planar antenna play a key role in the mixer operation. Improvement of the quality of the contacts leads simultaneously to a decrease in the noise temperature and an increase in the gain bandwidth of a mixer. |
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0033-8443 |
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1170 |
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