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Author Sidorova, M. V.; Kozorezov, A. G.; Semenov, A. V.; Korneev, A. A.; Chulkova, G. M.; Korneeva, Y. P.; Mikhailov, M. Y.; Devizenko, A. Y.; Goltsman, G. N. url  openurl
  Title Non-bolometric bottleneck in electron-phonon relaxation in ultra-thin WSi film Type Miscellaneous
  Year 2018 Publication (up) arXiv Abbreviated Journal  
  Volume Issue Pages  
  Keywords WSi films, diffusion constant, SSPD, SNSPD  
  Abstract We developed the model of the internal phonon bottleneck to describe the energy exchange between the acoustically soft ultrathin metal film and acoustically rigid substrate. Discriminating phonons in the film into two groups, escaping and nonescaping, we show that electrons and nonescaping phonons may form a unified subsystem, which is cooled down only due to interactions with escaping phonons, either due to direct phonon conversion or indirect sequential interaction with an electronic system. Using an amplitude-modulated absorption of the sub-THz radiation technique, we studied electron-phonon relaxation in ultrathin disordered films of tungsten silicide. We found an experimental proof of the internal phonon bottleneck. The experiment and simulation based on the proposed model agree well, resulting in tau{e-ph} = 140-190 ps at TC = 3.4 K, supporting the results of earlier measurements by independent techniques.  
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  Notes Duplicated as 1305 Approved no  
  Call Number Serial 1341  
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Author Murphy, A.; Semenov, A.; Korneev, A.; Korneeva, Y.; Gol’tsman, G.; Bezryadin, A. url  openurl
  Title Dark counts initiated by macroscopic quantum tunneling in NbN superconducting photon detectors Type Miscellaneous
  Year 2014 Publication (up) arXiv Abbreviated Journal  
  Volume Issue Pages  
  Keywords NbN SSPD  
  Abstract We perform measurements of the switching current distributions of three w = 120 nm wide, 4 nm thick NbN superconducting strips which are used for single-photon detectors. These strips are much wider than the diameter the vortex cores, so they are classified as quasi-two-dimensional (quasi-2D). We discover evidence of macroscopic quantum tunneling by observing the saturation of the standard deviation of the switching distributions at temperatures around 2 K. We analyze our results using the Kurkijarvi-Garg model and find that the escape temperature also saturates at low temperatures, confirming that at sufficiently low temperatures, macroscopic quantum tunneling is possible in quasi-2D strips and can contribute to dark counts observed in single photon detectors.  
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  Notes Approved no  
  Call Number murphy2014dark Serial 1356  
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Author Shangina, E. L.; Smirnov, K. V.; Morozov, D. V.; Kovalyuk, V. V.; Gol’tsman, G. N.; Verevkin, A. A.; Toropov, A. I. url  doi
openurl 
  Title Concentration dependence of the intermediate frequency bandwidth of submillimeter heterodyne AlGaAs/GaAs nanostructures Type Journal Article
  Year 2010 Publication (up) Bull. Russ. Acad. Sci. Phys. Abbreviated Journal Bull. Russ. Acad. Sci. Phys.  
  Volume 74 Issue 1 Pages 100-102  
  Keywords 2DEG AlGaAs/GaAs heterostructures, THz heterodyne detectors, IF bandwidth  
  Abstract The concentration dependence of the intermediate frequency bandwidth of heterodyne AlGaAs/GaAs detectors with 2D electron gas is measured using submillimeter spectroscopy with high time resolution at T= 4.2 K. The intermediate frequency bandwidth f3dBfalls from 245 to 145 MHz with increasing concentration of 2D electrons n s = (1.6-6.6) × 10[su11] cm-2. The dependence f3dB ≈ n s – 0.04±is observed in the studied concentration range; this dependence is determined by electron scattering by the deformation potential of acoustic phonons and piezoelectric scattering.  
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  ISSN 1062-8738 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 1217  
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Author Dube, I.; Jiménez, D.; Fedorov, G.; Boyd, A.; Gayduchenko, I.; Paranjape, M.; Barbara, P. url  doi
openurl 
  Title Understanding the electrical response and sensing mechanism of carbon-nanotube-based gas sensors Type Journal Article
  Year 2015 Publication (up) Carbon Abbreviated Journal Carbon  
  Volume 87 Issue Pages 330-337  
  Keywords carbon nanotubes, CNT detectors, field effect transistors, FET  
  Abstract Gas sensors based on carbon nanotube field effect transistors (CNFETs) have outstanding sensitivity compared to existing technologies. However, the lack of understanding of the sensing mechanism has greatly hindered progress on calibration standards and customization of these nano-sensors. Calibration requires identifying fundamental transistor parameters and establishing how they vary in the presence of a gas. This work focuses on modeling the electrical response of CNTFETs in the presence of oxidizing (NO2) and reducing (NH3) gases and determining how the transistor characteristics are affected by gas-induced changes of contact properties, such as the Schottky barrier height and width, and by the doping level of the nanotube. From the theoretical fits of the experimental transfer characteristics at different concentrations of NO2 and NH3, we find that the CNTFET response can be modeled by introducing changes in the Schottky barrier height. These changes are directly related to the changes in the metal work function of the electrodes that we determine experimentally, independently, with a Kelvin probe. Our analysis yields a direct correlation between the ON – current and the changes in the electrode metal work function. Doping due to molecules adsorbed at the carbon-nanotube/metal interface also affects the transfer characteristics.  
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  ISSN 0008-6223 ISBN Medium  
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  Notes Approved no  
  Call Number Serial 1778  
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Author Gayduchenko, I. A.; Fedorov, G. E.; Ibragimov, R. A.; Stepanova, T. S.; Gazaliev, A. S.; Vysochanskiy, N. A.; Bobrov, Y. A.; Malovichko, A. M.; Sosnin, I. M.; Bobrinetskiy, I. I. url  doi
openurl 
  Title Synthesis of single-walled carbon nanotube networks using monodisperse metallic nanocatalysts encapsulated in reverse micelles Type Journal Article
  Year 2016 Publication (up) Chem. Ind. Belgrade Abbreviated Journal Chem. Ind. Belgrade  
  Volume 70 Issue 1 Pages 1-8  
  Keywords carbon nanotubes, CNT, reverse micelles  
  Abstract We report on a method of synthesis of single-walled carbon nanotubes percolated networks on silicon dioxide substrates using monodisperse Co and Ni catalyst. The catalytic nanoparticles were obtained by modified method of reverse micelles of bis-(2-ethylhexyl) sulfosuccinate sodium in isooctane solution that provides the nanoparticle size control in range of 1 to 5 nm. The metallic nanoparticles of Ni and Co were characterized using transmission electron microscopy (TEM) and atomic-force microscopy (AFM). Carbon nanotubes were synthesized by chemical vapor deposition of CH4/H2 composition at temperature 1000 °С on catalysts pre-deposited on silicon dioxide substrate. Before temperature treatment during the carbon nanotube synthesis most of the catalyst material agglomerates due to magnetic forces while during the nanotube growth disintegrates into the separate nanoparticles with narrow diameter distribution. The formed nanotube networks were characterized using AFM, scanning electron microscopy (SEM) and Raman spectroscopy. We find that the nanotubes are mainly single-walled carbon nanotubes with high structural perfection up to 200 μm long with diameters from 1.3 to 1.7 nm consistent with catalyst nanoparticles diameter distribution and independent of its material.  
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  ISSN 0367-598X ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 1779  
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