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Yang, Z. Q., Hajenius, M., Baselmans, J. J. A., Gao, J. R., Klapwijk, T. M., Voronov, B., et al. (2005). Improved sensitivity of NbN hot electron bolometer mixers by vacuum baking. In Proc. 16th Int. Symp. Space Terahertz Technol. (pp. 222–225).
Abstract: We find that the sensitivity of heterodyne receivers based on superconducting hot-electron bolometer (HEB) in- creases by 25 − 30% after baking at 85 o C and in a high vacuum. The devices studied are twin-slot antenna coupled HEB mixers with a small NbN bridge of 1×0.15 μm 2 . The mixer noise temperature, gain, and resistance versus temperature curve of a HEB before and after baking are compared and analyzed. We show that baking reduces the intrinsic noise of the mixer by 37 % and makes the superconducting transition of the bridge and the contacts sharper. We argue that the reduction of the noise is due to the improvement of the transparency of the contact/film interface. The lowest receiver noise temperature of 700 K is measured at a local oscillator frequency of 1.63 THz and a bath temperature of 4.3 K.
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Seliverstov, S. V., Rusova, A. A., Kaurova, N. S., Voronov, B. M., & Goltsman, G. N. (2016). Attojoule energy resolution of direct detector based on hot electron bolometer. In J. Phys.: Conf. Ser. (Vol. 741, 012165 (1 to 5)). IOP Publishing.
Abstract: We characterize superconducting antenna-coupled NbN hot-electron bolometer (HEB) for direct detection of THz radiation operating at a temperature of 9.0 K. At signal frequency of 2.5 THz, the measured value of the optical noise equivalent power is 2.0×10-13 W-Hz-0.5. The estimated value of the energy resolution is about 1.5 aJ. This value was confirmed in the experiment with pulsed 1.55-μm laser employed as a radiation source. The directly measured detector energy resolution is 2 aJ. The obtained risetime of pulses from the detector is 130 ps. This value was determined by the properties of the RF line. These characteristics make our detector a device-of-choice for a number of practical applications associated with detection of short THz pulses.
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Kuznetsov, K. A., Kornienko, V. V., Vakhtomin, Y. B., Pentin, I. V., Smirnov, K. V., & Kitaeva, G. K. (2018). Generation and detection of optical-terahertz biphotons via spontaneous parametric downconversion. In Proc. ICLO (303).
Abstract: We study spontaneous parametric downconversion (SPDC) in the strongly non-degenerate regime when the idler wave hits the terahertz range. By using the hot-electron bolometer, for the first time the SPDC-generated idler-wave photons were directly detected in the terahertz frequency range. Spectrum of corresponding signal photons was measured using standard technique by the CCD camera. Possible applications of correlated optical-terahertz biphotons are discussed.
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Tretyakov, I., Kaurova, N., Raybchun, S., Goltsman, G. N., & Silaev, A. A. (2018). Technology for NbN HEB based multipixel matrix of THz range. In EPJ Web Conf. (Vol. 195, 05011).
Abstract: The influence of homogeneity disorder degree of the thin superconducting NbN film across of Si wafer on characteristics of the Hot Electron Bolometers (HEB) has been investigated. Our experiments have been carried out near the superconducting transition and far below it. The high homogeneity disorder degree of the NbN film has been achieved by preparing the Si substrate surface. The fabricated HEBs all have almost identical R (T) characteristics with a dispersion of Tc and the normal resistance R300 of not more than 0.15K and 2 Ω, respectively. The quality of the devises allows us to demonstrate clearly the influence of non-equilibrium processes in the S’SS’ system on the device performance. Our fabrication technology also allows creating multiplex heterodyne and direct detector matrices based the HEB devices.
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Maslennikova, A., Larionov, P., Ryabchun, S., Smirnov, A., Pentin, I., Vakhtomin, Y., et al. (2011). Noise equivalent power and dynamic range of NBN hot-electron bolometers. In Proc. MLPLIT (pp. 146–148). Modern laser physics and laser-information technologies for science and manufacture.
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Селиверстов, С. В., Финкель, М. И., Рябчун, С. А., Воронов, Б. М., Каурова, Н. С., Селезнев, В. А., et al. (2014). Терагерцевый сверхпроводниковый детектор с аттоджоулевым энергетическим разрешением и постоянной времени 25 пс. In Труды XVIII международного симпозиума «Нанофизика и наноэлектроника» (Vol. 1, pp. 91–92).
Abstract: Представлены результаты измерения энергетического разрешения терагерцевого сверхпроводникового NbN-детектора на эффектеэлектронного разогрева, работающего при температуре около 10 К. Использование инновационной in situ технологии производства привело к существенному улучшению чувствительности детектора. Увеличение быстродействия детектора было достигнуто за счет реализации дополнительного диффузионного канала охла-ждения электронной подсистемы. Измеренное значение эквивалентной мощности шума на частоте 2.5 ТГц составило 2.0×10-13Вт•Гц-0.5, постоянной времени 25 пс. Соответствующее расчетное значение энергетического разрешения составило 2.5 аДж.
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Titova, N. A., Baeva, E. M., Kardakova, A. I., & Goltsman, G. N. (2020). Fabrication of NbN/SiNx:H/SiO2 membrane structures for study of heat conduction at low temperatures. In J. Phys.: Conf. Ser. (Vol. 1695, 012190).
Abstract: 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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Корнеев, А. А., Окунев, О. В., Чулкова, Г. М., Смирнов, К. В., Милостная, И. И., Минаева, О. В., et al. (2015). Спонтанные и фотоиндуцированные резистивные состояния в узких сверхпроводящих NbN полосках. МПГУ.
Abstract: Монография посвящена актуальной проблеме современной фотоники: разработке высокочувствительных и быстродействующих сверхпроводниковых однофотонных детекторов на основе тонкой пленки NbN. В работе исследуются неравновесные процессы, протекающие в тонкой сверхпроводящей пленке после поглощения инфракрасного фотона и приводящие к возникновению резистивного состояния. На этих процессах основан механизм фотоотклика исследуемого в работе однофотонного детектора. В частности, исследуются зависимости квантовой эффективности и скорости темнового счета от геометрических параметров детектора: толщины пленки, ширины полоски, а также от величины транспортного тока детектора. Монография предназначена для студентов старших курсов, аспирантов и начинающих исследователей, работающих в области сверхпроводниковой наноэлектроники и радиофизики.
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Beck, M., Leiderer, P., Kabanov, V. V., Gol'tsman, G., Helm, M., & Demsar, J. (2012). Energy-gap dynamics of a superconductor NbN studied by time-resolved terahertz spectroscopy. In INIS (Vol. 45, pp. 1–3).
Abstract: Using time-resolved terahertz (THz) spectroscopy we performed direct studies of the photoinduced suppression and recovery of the SC gap in a conventional SC NbN. Both processes are found to be strongly temperature and excitation density dependent. The analysis of the data with the established phenomenological Rothwarf-Taylor model enabled us to determine the important microscopic constants: the Cooper pair-breaking rate via phonon absorption and the bare quasiparticle recombination rate. From the latter we were able to extract the dimensionless electron-phonon coupling constant, λ=1.1±0.1, in excellent agreement with theoretical estimates. The technique also allowed us to determine the absorbed energy required to suppress SC, which in NbN equals the thermodynamic condensation energy (in cuprates the two differ by an order of magnitude). Finally, we present the first studies of dynamics following resonant excitation with intense narrow band THz pulses tuned to above and below the superconducting gap. These suggest an additional process, particularly pronounced near Tc, that could be attributed to amplification of SC via effective quasiparticle cooling.
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Karasik, B. S., Il'in, K. S., Ptitsina, N. G., Gol'tsman, G. N., Gershenzon, E. M., Pechen', E. V., et al. (1998). Electron-phonon scattering rate in impure NbC films. In NASA/ADS (Y35.08).
Abstract: The study of the electron-phonon interaction in thin (20 nm) NbC films with electron mean free path l=2-13 nm gives an evidence that electron scattering is significantly modified due to the interference between electron-phonon and elastic electron scattering from impurities. The interference ~T^2-term, which is proportional to the residual resistivity, dominates over the Bloch-Grüneisen contribution to resistivity at low temperatures up to 60 K. The electron energy relaxation rate is directly measured via the relaxation of hot electrons heated by modulated electromagnetic radiation. In the temperature range 1.5 – 10 K the relaxation rate shows a weak dependence on the electron mean free path and strong temperature dependence T^n with the exponent n = 2.5-3. This behaviour is well explained by the theory of the electron-phonon-impurity interference taking into account the electron coupling with transverse phonons determined from the resistivity data.
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