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Author |
Dube, I.; Jiménez, D.; Fedorov, G.; Boyd, A.; Gayduchenko, I.; Paranjape, M.; Barbara, P. |
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Title |
Understanding the electrical response and sensing mechanism of carbon-nanotube-based gas sensors |
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Journal Article |
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Year |
2015 |
Publication |
Carbon |
Abbreviated Journal |
Carbon |
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Volume |
87 |
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Pages |
330-337 |
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Keywords |
carbon nanotubes, CNT detectors, field effect transistors, FET |
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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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0008-6223 |
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1778 |
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Author |
Sergeev, A. V.; Livanov, D. V. |
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Title |
Phonon renormalization of thermoelectric power of high-Tc materials |
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Conference Article |
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Year |
1993 |
Publication |
Phonon Scattering in Condensed Matter VII. Springer Series in Solid-State Sciences |
Abbreviated Journal |
Phonon Scattering in Condensed Matter VII. Springer Series in Solid-State Sciences |
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112 |
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204-205 |
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HTS, YBCO |
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Abstract |
Renormalization of thermoelectric power due to Nielsen — Taylor effect (interference between electron-phonon and electron- impurity interactions) is used for the explanation of the temperature dependence and sign of the thermopower in high-Tc materials. In the framework of the model the negative sign of TEP of untwinned YBa2Cu3O7−x crystal in a-direction observed by Howson et. al. is connected to the strong hole scattering via O-vacancies in chains. |
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Meissner, M.; Pohl, R. O. |
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Seventh International Conference, Cornell University, Ithaca, New York, August 3-7, 1992 |
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1664 |
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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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2020 |
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JETP Lett. |
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Jetp Lett. |
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Volume |
111 |
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2 |
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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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Sidorova, M.; Semenov, A.; Hübers, H.-W.; Kuzmin, A.; Doerner, S.; Ilin, K.; Siegel, M.; Charaev, I.; Vodolazov, D. |
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Title |
Timing jitter in photon detection by straight superconducting nanowires: Effect of magnetic field and photon flux |
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Journal Article |
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Year |
2018 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
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Volume |
98 |
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13 |
Pages |
134504 (1 to 14) |
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Keywords |
SNSPD, NbN namowires |
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Abstract |
We studied the effects of the external magnetic field and photon flux on timing jitter in photon detection by straight superconducting NbN nanowires. At two wavelengths 800 and 1560 nm, statistical distribution in the appearance times of photon counts exhibits Gaussian shape at small times and an exponential tail at large times. The characteristic exponential time is larger for photons with smaller energy and increases with external magnetic field while variations in the Gaussian part of the distribution are less pronounced. Increasing photon flux drives the nanowire from the discrete quantum detection regime to the uniform bolometric regime that averages out fluctuations of the total number of nonequilibrium electrons created by the photon and drastically reduces jitter. The difference between standard deviations of Gaussian parts of distributions for these two regimes provides the measure for the strength of electron-number fluctuations; it increases with the photon energy. We show that the two-dimensional hot-spot detection model explains qualitatively the effect of magnetic field. |
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2469-9950 |
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1842 |
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Author |
Sergeev, A.; Mitin, V. |
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Title |
Electron-phonon interaction in disordered conductors: Static and vibrating scattering potentials |
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Journal Article |
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Year |
2000 |
Publication |
Phys. Rev. B. |
Abbreviated Journal |
Phys. Rev. B. |
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Volume |
61 |
Issue |
9 |
Pages |
6041-6047 |
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Keywords |
disordered conductors, scattering potential, electron-phonon interaction |
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Employing the Keldysh diagram technique, we calculate the electron-phonon energy relaxation rate in a conductor with the vibrating and static δ-correlated random electron-scattering potentials. If the scattering potential is completely dragged by phonons, this model yields the Schmid’s result for the inelastic electron-scattering rate τ−1e−ph. At low temperatures the effective interaction decreases due to disorder, and τ−1e−ph∝T4l (l is the electron mean-free path). In the presense of the static potential, quantum interference of numerous scattering processes drastically changes the effective electron-phonon interaction. In particular, at low temperatures the interaction increases, and τ−1e−ph∝T2/l. Along with an enhancement of the interaction, which is observed in disordered metallic films and semiconducting structures at low temperatures, the suggested model allows us to explain the strong sensitivity of the electron relaxation rate to the microscopic quality of a particular film. |
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0163-1829 |
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307 |
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Ptitsina, N. G.; Chulkova, G. M.; Il’in, K. S.; Sergeev, A. V.; Pochinkov, F. S.; Gershenzon, E. M.; Gershenson, M. E. |
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Electron-phonon interaction in disordered metal films: The resistivity and electron dephasing rate |
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Journal Article |
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1997 |
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Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
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56 |
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16 |
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10089-10096 |
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disordered metal films, electron-phonon interaction, electron dephasing rate, resistivity |
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The temperature dependence of the resistance of films of Al, Be, and NbC with small values of the electron mean free path l=1.5–10nm has been measured at 4.2–300 K. The resistance of all the films contains a T2 contribution that is proportional to the residual resistance; this contribution has been attributed to the interference between the elastic electron scattering and the electron-phonon scattering. Fitting the data to the theory of the electron-phonon-impurity interference (M. Yu. Reiser and A. V. Sergeev, Zh. Eksp. Teor. Fiz. 92, 224 (1987) [Sov. Phys. JETP 65, 1291 (1987)]), we obtain constants of interaction of the electrons with transverse phonons, and estimate the contribution of this interaction to the electron dephasing rate in thin films of Au, Al, Be, Nb, and NbC. Our estimates are in a good agreement with the experimental data on the inelastic electron-phonon scattering in these films. This indicates that the interaction of electrons with transverse phonons controls the electron-phonon relaxation rate in thin-metal films over a broad temperature range. |
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0163-1829 |
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1766 |
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Zhang, X.; Lita, A. E.; Smirnov, K.; Liu, H. L.; Zhu, D.; Verma, V. B.; Nam, S. W.; Schilling, A. |
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Title |
Strong suppression of the resistivity near the superconducting transition in narrow microbridges in external magnetic fields |
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Journal Article |
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2020 |
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Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
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Volume |
101 |
Issue |
6 |
Pages |
060508 (1 to 6) |
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Keywords |
MoSi, WSi films |
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We have investigated a series of superconducting bridges based on homogeneous amorphous WSi and MoSi films, with bridge widths w ranging from 2 to 1000μm and film thicknesses d∼4−6 and 100 nm. Upon decreasing the bridge widths below the respective Pearl lengths, we observe in all cases distinct changes in the characteristics of the resistive transitions to superconductivity. For each of the films, the resistivity curves R(B,T) separate at a well-defined and field-dependent temperature T∗(B) with decreasing the temperature, resulting in a dramatic suppression of the resistivity and a sharpening of the transitions with decreasing bridge width w. The associated excess conductivity in all the bridges scales as 1/w, which may suggest either the presence of a highly conducting region that is dominating the electric transport, or a change in the vortex dynamics in narrow enough bridges. We argue that this effect can only be observed in materials with sufficiently weak vortex pinning. |
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1800 |
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Vodolazov, D. Y.; Manova, N. N.; Korneeva, Y. P.; Korneev, A. A. |
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Title |
Timing jitter in NbN superconducting microstrip single-photon detector |
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Journal Article |
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2020 |
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Phys. Rev. Applied |
Abbreviated Journal |
Phys. Rev. Applied |
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Volume |
14 |
Issue |
4 |
Pages |
044041 (1 to 8) |
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Keywords |
NbN SSPD, SNSPD |
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We experimentally study timing jitter of single-photon detection by NbN superconducting strips with width w ranging from 190 nm to 3μm. We find that timing jitter of both narrow (190 nm) and micron-wide strips is about 40 ps at currents where internal detection efficiency η saturates and it is close to our instrumental jitter. We also calculate intrinsic timing jitter in wide strips using the modified time-dependent Ginzburg-Landau equation coupled with a two-temperature model. We find that with increasing width the intrinsic timing jitter increases and the effect is most considerable at currents where a rapid growth of η changes to saturation. We relate it with complicated vortex and antivortex dynamics, which depends on a photon’s absorption site across the strip and its width. The model also predicts that at current close to depairing current the intrinsic timing jitter of a wide strip could be about ℏ/kBTc (Tc is a critical temperature of superconductor), i.e., the same as for a narrow strip. |
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2331-7019 |
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1788 |
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Korneeva, Y. P.; Manova, N. N.; Florya, I. N.; Mikhailov, M. Y.; Dobrovolskiy, O. V.; Korneev, A. A.; Vodolazov, D. Y. |
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Title |
Different single-photon response of wide and narrow superconducting MoxSi1−x strips |
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Journal Article |
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2020 |
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Phys. Rev. Applied |
Abbreviated Journal |
Phys. Rev. Applied |
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Volume |
13 |
Issue |
2 |
Pages |
024011 (1 to 7) |
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MoSi SSPD, SNSPD |
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The photon count rate (PCR) of superconducting single-photon detectors made of MoxSi1−x films shaped as a 2-μm-wide strip and a 115-nm-wide meander strip line is studied experimentally as a function of the dc biasing current at different values of the perpendicular magnetic field. For the wide strip, a crossover current Icross is observed, below which the PCR increases with an increasing magnetic field and above which it decreases. This behavior contrasts with the narrow MoxSi1−x meander, for which no crossover current is observed, thus suggesting different photon-detection mechanisms in the wide and narrow strips. Namely, we argue that in the wide strip the absorbed photon destroys superconductivity locally via the vortex-antivortex mechanism for the emergence of resistance, while in the narrow meander superconductivity is destroyed across the whole strip line, forming a hot belt. Accordingly, the different photon-detection mechanisms associated with vortices and the hot belt determine the qualitative difference in the dependence of the PCR on the magnetic field. |
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1790 |
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Zolotov, P.; Divochiy, A.; Vakhtomin, Y.; Seleznev, V.; Morozov, P.; Smirnov, K. |
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Superconducting single-photon detectors made of ultra-thin VN films |
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Conference Article |
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2018 |
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KnE Energy |
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KnE Energy |
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3 |
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3 |
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83-89 |
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We optimized technology of thin VN films deposition in order to study VN-based superconducting single-photon detectors. Investigation of the main VN film parameters showed that this material has lower resistivity compared to commonly used NbN. Fabricated from obtained films devices showed 100% intrinsic detection efficiency at 900 nm, at the temperature of 1.7 K starting with the bias current of 0.7·I |
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