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Ovchinnikov, O. V.; Perepelitsa, A. S.; Smirnov, M. S.; Latyshev, A. N.; Grevtseva, I. G.; Vasiliev, R. B.; Goltsman, G. N.; Vitukhnovsky, A. G. |
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Title |
Luminescence of colloidal Ag2S/ZnS core/shell quantum dots capped with thioglycolic acid |
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Journal Article |
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Year |
2020 |
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J. Luminescence |
Abbreviated Journal |
J. Luminescence |
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220 |
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117008 (1 to 7) |
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Ag2S QD, quantum dots |
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The features of IR luminescence of colloidal AgS QDs passivated with thioglycolic acid (AgS/TGA) under the formation of AgS/ZnS/TGA core/shell QDs are considered. A 4.5-fold increase in the quantum yield of recombination IR luminescence within the band with a peak at 960 nm (1.29 eV), full width at half maximum of 250 nm (0.34 eV), and the Stokes shift with respect to the exciton absorption of 0.6 eV was found. The increase in the IR luminescence intensity of AgS/ZnS/TGA QDs is accompanied by an increase in the average luminescence lifetime from 2.9 ns to 14.3 ns, which is explained as “healing” of surface trap states during the formation of the ZnS shell. For the first time, the enhancement of the luminescence intensity photodegradation (hereinafter referred to as fatigue) was found during the formation of the AgS/ZnS/TGA core/shell QDs. The luminescence fatigue is irreversible. We conclude that the initial stage of photolysis of the AgS core QDs under laser irradiation plays a key role. Low-atomic photolytic clusters of silver formed on the AgS core QDs act as luminescence quenching centers and do not reveal structural transformations into AgS, provided that the clusters are not in contact with TGA. |
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0022-2313 |
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1267 |
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Emelianov, A. V.; Nekrasov, N. P.; Moskotin, M. V.; Fedorov, G. E.; Otero, N.; Romero, P. M.; Nevolin, V. K.; Afinogenov, B. I.; Nasibulin, A. G.; Bobrinetskiy, I. I. |
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Title |
Individual SWCNT transistor with photosensitive planar junction induced by two‐photon oxidation |
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Journal Article |
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Year |
2021 |
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Adv. Electron. Mater. |
Abbreviated Journal |
Adv. Electron. Mater. |
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Volume |
7 |
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3 |
Pages |
2000872 |
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SWCNT transistors |
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The fabrication of planar junctions in carbon nanomaterials is a promising way to increase the optical sensitivity of optoelectronic nanometer-scale devices in photonic connections, sensors, and photovoltaics. Utilizing a unique lithography approach based on direct femtosecond laser processing, a fast and easy technique for modification of single-walled carbon nanotube (SWCNT) optoelectronic properties through localized two-photon oxidation is developed. It results in a novel approach of quasimetallic to semiconducting nanotube conversion so that metal/semiconductor planar junction is formed via local laser patterning. The fabricated planar junction in the field-effect transistors based on individual SWCNT drastically increases the photoresponse of such devices. The broadband photoresponsivity of the two-photon oxidized structures reaches the value of 2 × 107 A W−1 per single SWCNT at 1 V bias voltage. The SWCNT-based transistors with induced metal/semiconductor planar junction can be applied to detect extremely small light intensities with high spatial resolution in photovoltaics, integrated circuits, and telecommunication applications. |
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2199-160X |
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1843 |
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Verevkin, A. I.; Ptitsina, N. G.; Chulkova, G. M.; Gol'tsman, G. N.; Gershenzon, E. M.; Yngvesson, K. S. |
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Title |
Electron energy relaxation in a 2D channel in AlGaAs-GaAs heterostructures under quasiequilibrium conditions at low temperatures |
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1995 |
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JETP Lett. |
Abbreviated Journal |
JETP Lett. |
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61 |
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7 |
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591-595 |
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2DEG, AlGaAs/GaAs heterostructures |
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The energy relaxation time of 2D electrons, Te, has been measured under quasiequilibrium conditions in AlGaAs—GaAs heterojunctions over the temperature range T= 1.5—20 K. At T> 4 K, Te depends only weakly on the temperature, while at T< 4 K 7;'(T) there is a dependence fr; lNT. A linear dependence 7: 1 (T) in the Bloch—-Grfineisen temperature region (T< 5 K) is unambiguous evidence that a piezoacoustic mechanism of an electron—phonon interaction is predominant in the inelastic scattering of electrons. The values of T6 in this temperature range agree very accurately with theoretical results reported by Karpus [Sov. Phys. Semicond. 22 (1988)]. At higher temperatures, where scat—tering by deformation acoustic phonons becomes substantial, there is a significant discrepancy between the experimental and theoretical re-sults. |
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1624 |
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Sergeev, A.; Karasik, B. S.; Ptitsina, N. G.; Chulkova, G. M.; Il'in, K. S.; Gershenzon, E. M. |
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Title |
Electron–phonon interaction in disordered conductors |
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Journal Article |
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1999 |
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Phys. Rev. B Condens. Matter |
Abbreviated Journal |
Phys. Rev. B Condens. Matter |
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263-264 |
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190-192 |
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disordered conductors, electron-phonon interaction |
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The electron–phonon interaction is strongly modified in conductors with a small value of the electron mean free path (impure metals, thin films). As a result, the temperature dependencies of both the inelastic electron scattering rate and resistivity differ significantly from those for pure bulk materials. Recent complex measurements have shown that modified dependencies are well described at K by the electron interaction with transverse phonons. At helium temperatures, available data are conflicting, and cannot be described by an universal model. |
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0921-4526 |
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1765 |
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Nikoghosyan, A. S.; Martirosyan, R. M.; Hakhoumian, A. A.; Makaryan, A. H.; Tadevosyan, V. R.; Goltsman, G. N.; Antipov, S. V. |
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Title |
Effect of absorption on the efficiency of THz radiation generation in a nonlinear crystal placed into a waveguide |
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Journal Article |
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2018 |
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Armenian J. Phys. |
Abbreviated Journal |
Armenian J. Phys. |
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11 |
Issue |
4 |
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257-262 |
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THz, waveguide, nonlinear crystal |
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The effect of THz radiation absorption on the efficiency of generation of coherent THz radiation in a nonlinear optical crystal placed into a metal rectangular waveguide is studied. The efficiency of the nonlinear conversion of optical laser radiation to the THz band is also a function of the phase-matching (PM) condition inside the nonlinear crystal. The method of partial filling of a metal waveguide with a nonlinear optical crystal is used to ensure phase matching. Phase matching was obtained by the proper choice of the thickness of the nonlinear crystal, namely the degree of partial filling of the waveguide. We have studied the THz radiation attenuation caused by the losses in both the metal walls of the waveguide and in the crystal, taking into account the dimension of the cross section of the waveguide, the degree of partial filling and its dielectric constant. |
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1829-1171 |
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1291 |
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Eletskii, A. V.; Sarychev, A. K.; Boginskaya, I. A.; Bocharov, G. S.; Gaiduchenko, I. A.; Egin, M. S.; Ivanov, A. V.; Kurochkin, I. N.; Ryzhikov, I. A.; Fedorov, G. E. |
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Amplification of a Raman scattering signal by carbon nanotubes |
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Journal Article |
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2018 |
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Dokl. Phys. |
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Dokl. Phys. |
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63 |
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12 |
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496-498 |
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carbon nanotubes, CNT, Raman scattering, RLS |
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The effect of Raman scattering (RLS) signal amplification by carbon nanotubes (CNTs) was studied. Single-layered nanotubes were synthesized by the chemical vapor deposition (CVD) method using methane as a carbon-containing gas. The object of study used was water, the Raman spectrum of which is rather well known. Amplification of the Raman scattering signal by several hundred percent was attained in our work. The maximum amplification of a Raman scattering signal was shown to be achieved at an optimal density of nanotubes on a substrate. This effect was due to the scattering and screening of plasmons excited in CNTs by neighboring nanotubes. The amplification mechanism and the possibilities of optimization for this effect were discussed on the basis of the theory of plasmon resonance in carbon nanotubes. |
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1028-3358 |
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1775 |
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Gershenzon, E. M.; Gershenzon, M. E.; Gol'tsman, G. N.; Semenov, A. D.; Sergeev, A. V. |
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Title |
Heating of electrons in a superconductor in the resistive state by electromagnetic radiation |
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Journal Article |
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1984 |
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Sov. Phys. JETP |
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Sov. Phys. JETP |
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59 |
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2 |
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442-450 |
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Nb HEB |
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The effect of heating of electrons relative to phonons is observed and investigated in a superconducting film that is made resistive by current and by an external magnetic field. The effect is manifested by an increase of the film resistance under the influence of the electromagnetic radiation, and is not selective in the frequency band 10^10-10^15 Hz. The independence of the effect of frequency under conditions of strong scattering by static defects is attributed to the decisive role of electron-electron collisions in the distribution function. The experimentally obtained characteristic time of resistance variation near the superconducting transition corresponds to the relaxation time of the order parameter, while at lower temperatures and fields it corresponds to the time of the inelastic electron-phonon interaction. |
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RPLAB @ phisix @ |
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983 |
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Gershenzon, E. M.; Gershenzon, M. E.; Gol'tsman, G. N.; Semyonov, A. D.; Sergeev, A. V. |
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Heating of electrons in superconductor in the resistive state due to electromagnetic radiation |
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Journal Article |
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1984 |
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Solid State Communications |
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Solid State Communications |
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50 |
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3 |
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207-212 |
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Nb HEB |
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The effect of heating electrons with respect to phonons in a thin superconducting film driven into the resistive state by the current and the external magnetic field has been observed and investigated. This effect caused by the electromagnetic radiation is manifested in the increased resistance of the film and is not selective over the frequency range from 1010 to 1015 Hz. That the effect is frequency independent under the conditions of strong electron scattering caused by static defects is explained by the decisive role of electron -electron collisions in forming the distribution function. The characteristic time of resistance change, obtained experimentally, corresponds to the relaxation time of the order parameter near the superconducting transition and to the relaxation time of the nonelastic electron-phonon interaction at lower temperatures and in lower magnetic fields. |
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0038-1098 |
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1709 |
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Shurakov, A.; Lobanov, Y.; Goltsman, G. |
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Superconducting hot-electron bolometer: from the discovery of hot-electron phenomena to practical applications |
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Journal Article |
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2015 |
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Supercond. Sci. Technol. |
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Supercond. Sci. Technol. |
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29 |
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2 |
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023001 |
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HEB |
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The discovery of hot-electron phenomena in a thin superconducting film in the last century was followed by numerous experimental studies of its appearance in different materials aiming for a better understanding of the phenomena and consequent implementation of terahertz detection systems for practical applications. In contrast to the competitors such as superconductor-insulator-superconductor tunnel junctions and Schottky diodes, the hot electron bolometer (HEB) did not demonstrate any frequency limitation of the detection mechanism. The latter, in conjunction with a decent performance, rapidly made the HEB mixer the most attractive candidate for heterodyne observations at frequencies above 1 THz. The successful operation of practical instruments (the Heinrich Hertz Telescope, the Receiver Lab Telescope, APEX, SOFIA, Hershel) ensures the importance of the HEB technology despite the lack of rigorous theoretical routine for predicting the performance. In this review, we provide a summary of experimental and theoretical studies devoted to understanding the HEB physics, and an overview of various fabrication routes and materials. |
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0953-2048 |
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1156 |
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Schwaab, G.W.; Sirmain, G.; Schubert, J.; Hubers, H.-W.; Gol'tsman, G.; Cherednichenko, S.; Verevkin, A.; Voronov, B.; Gershenzon, E. |
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Investigation of NbN phonon-cooled HEB mixers at 2.5 THz |
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1999 |
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IEEE Trans. Appl. Supercond. |
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IEEE Trans. Appl. Supercond. |
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9 |
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2 |
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4233-4236 |
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NbN HEB mixers |
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The development of superconducting hot electron bolometric (HEB) mixers has been a big step forward in the direction of quantum noise limited mixer performance at THz frequencies. Such mixers are crucial for the upcoming generation of airborne and spaceborne THz heterodyne receivers. In this paper we report on new results on a phonon-cooled NbN HEB mixer using e-beam lithography. The superconducting film is 3 nm thick. The mixer is 0.2 μm long and 1.5 μm wide and it is integrated in a spiral antenna on a Si substrate. The device is quasi-optically coupled through a Si lens and a dielectric beam combiner to the radiation of an optically pumped FIR ring gas laser cavity. The performance of the mixer at different THz frequencies from 0.69 to 2.55 THz with an emphasis on 2.52 THz is demonstrated. At 2.52 THz minimum DSB noise temperatures of 4200 K have been achieved at an IF of 1.5 GHz and a bandwidth of 40 MHz with the mixer mounted in a cryostat and a 0.8 m long signal path in air. |
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1051-8223 |
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