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Author Bulaevskii, L. N.; Graf, M. J.; Batista, C. D.; Kogan, V. G.
Title Vortex-induced dissipation in narrow current-biased thin-film superconducting strips Type Journal Article
Year 2011 Publication Phys. Rev. B Abbreviated Journal Phys. Rev. B
Volume 83 Issue 14 Pages 9
Keywords
Abstract A vortex crossing a thin-film superconducting strip from one edge to the other, perpendicular to the bias current, is the dominant mechanism of dissipation for films of thickness d on the order of the coherence length ξ and of width w much narrower than the Pearl length Λâ‰<ab>wâ‰<ab>ξ. At high bias currents I*<I<Ic the heat released by the crossing of a single vortex suffices to create a belt-like normal-state region across the strip, resulting in a detectable voltage pulse. Here Ic is the critical current at which the energy barrier vanishes for a single vortex crossing. The belt forms along the vortex path and causes a transition of the entire strip into the normal state. We estimate I* to be roughly Ic/3. Furthermore, we argue that such “hot” vortex crossings are the origin of dark counts in photon detectors, which operate in the regime of metastable superconductivity at currents between I* and Ic. We estimate the rate of vortex crossings and compare it with recent experimental data for dark counts. For currents below I*, that is, in the stable superconducting but resistive regime, we estimate the amplitude and duration of voltage pulses induced by a single vortex crossing.
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Notes SSPD Approved no
Call Number RPLAB @ gujma @ Serial 688
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Author Edlmayr, V.; Harzer, T. P.; Hoffmann, R.; Kiener, D.; Scheu, C.; Mitterer, C.
Title Effects of thermal annealing on the microstructure of sputtered Al2O3 coatings Type Journal Article
Year 2011 Publication J. Vac. Sci. Technol. A Abbreviated Journal
Volume 29 Issue 4 Pages 8
Keywords Annealing
Abstract The morphology and microstructure of Al2O3 thin films deposited by pulsed direct current magnetron sputtering were studied in the as-grown state and after vacuum annealing at 1000 °C for 12 h using transmission electron microscopy. For the coating deposited under low ion bombardment conditions, the film consists of small γ- and/or δ-Al2O3 grains embedded in an amorphous matrix. The grain size at the region close to the interface to the substrate was much larger than that of the remaining layer. Growth of the γ-Al2O3 phase is promoted during annealing but no transformation to α-Al2O3 was detected. For high-energetic growth conditions, clear evidence for γ-Al2O3 formation was found in the upper part of the coating with grain size much larger than for low-energetic growth, but the film was predominately amorphous at the interface region. Annealing resulted in the transformation of γ-Al2O3 to α-Al2O3, while the mainly amorphous part crystallized to γ-Al2O3.
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Notes Annealing Approved no
Call Number RPLAB @ gujma @ Serial 693
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Author Ozhegov, R. V.; Gorshkov, K. N.; Gol'tsman, G. N.; Kinev, N. V.; Koshelets, V. P.
Title The stability of a terahertz receiver based on a superconducting integrated receiver Type Journal Article
Year 2011 Publication Supercond. Sci. Technol. Abbreviated Journal Supercond. Sci. Technol.
Volume 24 Issue 3 Pages 035003
Keywords SIS mixer, SIR, stability
Abstract We present the results of stability testing of a terahertz radiometer based on a superconducting receiver with a SIS tunnel junction as the mixer and a flux-flow oscillator as the local oscillator. In the continuum mode, the receiver with a noise temperature of 95 K at 510 GHz measured over the intermediate frequency (IF) passband of 4-8 GHz offered a noise equivalent temperature difference of 10 ± 1 mK at an integration time of 1 s. We offer a method to significantly increase the integration time without the use of complex measurement equipment. The receiver observed a strong signal over a final detection bandwidth of 4 GHz and offered an Allan time of 5 s.
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Notes Approved no
Call Number RPLAB @ gujma @ Serial 705
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Author Флоря, И.Н.; Корнеева, Ю.П.; Корнеев, А.А.; Гольцман, Г.Н.
Title Сверхпроводниковый однофотонный детектор для среднего инфракрасного диапазона на основе узких параллельных полосок Type Journal Article
Year 2011 Publication Труды Московского физико-технического института Abbreviated Journal Труды МФТИ
Volume 3 Issue 2 Pages 14-17
Keywords SSPD
Abstract Мы рассматриваем ультрабыстрый сверхпроводниковый однофотонный детектор (SSPD). SSPD представляет собой тонкопленочную наноструктуру — очень узкую и длинную полоску сверхпроводника, изогнутую в виде меандра, изготовленную из пленки NbN толщиной 4 нм, нанесенной на сапфировую подложку. SSPD хорошо сопрягается с оптоволокном и легко может быть интегрирован в полностью готовую для работы приемную систему. В стремлении продвинуться в средний ИК диапозон нам удалось разработать SSPD в виде параллельно соединенных полосок с шириной полоски всего 50 нм и сохранить при этом сверхпроводящие свойства. Эти детекторы показывают более чем на порядок большую чувствительность на длине волны 3;5 мкм, чем SSPD в виде меандра. Полученные результаты открывают путь к эффективным детекторам среднего ИК-диапазона, обладающим скоростью счета свыше 1 ГГц.
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Notes Approved no
Call Number RPLAB @ gujma @ Serial 706
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Author Пентин, И. В.; Смирнов, К. В.; Вахтомин, Ю. Б.; Смирнов, А. В.; Ожегов, Р. В.; Дивочий, А. В.; Гольцман, Г. Н.
Title Быстродействующий терагерцевый приемник и инфракрасный счетчик одиночных фотонов на эффекте разогрева электронов в сверхпроводниковых тонкопленочных наноструктурах Type Journal Article
Year 2011 Publication Труды МФТИ Abbreviated Journal Труды МФТИ
Volume 3 Issue 2 Pages 38-42
Keywords SSPD, SNSPD, HEB
Abstract Представлены результаты создания приемных систем терагерцевого диапазона (0.3-70 ТГц), обладающих рекордным быстродействием (50 пс) и высокой чувствительностью (до 5x 10^(-14) Вт/Гц^(1/2)), а также однофотонных приемных систем ближнего инфракрасного диапазона с квантовой эффективностью 25 %, уровнем темнового счета 10-1c., максимальной скоростью счета ~ 100 МГц и временным разрешением до 50 пс.
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Notes Approved no
Call Number RPLAB @ gujma @ Serial 707
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