| Records |
| Author |
Dube, I.; Jiménez, D.; Fedorov, G.; Boyd, A.; Gayduchenko, I.; Paranjape, M.; Barbara, P. |
| Title |
Understanding the electrical response and sensing mechanism of carbon-nanotube-based gas sensors |
Type |
Journal Article |
| Year |
2015 |
Publication |
Carbon |
Abbreviated Journal |
Carbon |
| Volume |
87 |
Issue |
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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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0008-6223 |
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1778 |
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| Author |
Gayduchenko, I.; Kardakova, A.; Fedorov, G.; Voronov, B.; Finkel, M.; Jiménez, D.; Morozov, S.; Presniakov, M.; Goltsman, G. |
| Title |
Response of asymmetric carbon nanotube network devices to sub-terahertz and terahertz radiation |
Type |
Journal Article |
| Year |
2015 |
Publication |
J. Appl. Phys. |
Abbreviated Journal |
J. Appl. Phys. |
| Volume |
118 |
Issue |
19 |
Pages |
194303 |
| Keywords |
terahertz detectors, asymmetric carbon nanotubes, CNT |
| Abstract |
Demand for efficient terahertz radiation detectors resulted in intensive study of the asymmetric carbon nanostructures as a possible solution for that problem. It was maintained that photothermoelectric effect under certain conditions results in strong response of such devices to terahertz radiation even at room temperature. In this work, we investigate different mechanisms underlying the response of asymmetric carbon nanotube (CNT) based devices to sub-terahertz and terahertz radiation. Our structures are formed with CNT networks instead of individual CNTs so that effects probed are more generic and not caused by peculiarities of an individual nanoscale object. We conclude that the DC voltage response observed in our structures is not only thermal in origin. So called diode-type response caused by asymmetry of the device IV characteristic turns out to be dominant at room temperature. Quantitative analysis provides further routes for the optimization of the device configuration, which may result in appearance of novel terahertz radiation detectors. |
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0021-8979 |
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no |
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1169 |
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Ryzhii, V.; Otsuji, T.; Ryzhii, M.; Leiman, V. G.; Fedorov, G.; Goltzman, G. N.; Gayduchenko, I. A.; Titova, N.; Coquillat, D.; But, D.; Knap, W.; Mitin, V.; Shur, M. S. |
| Title |
Two-dimensional plasmons in lateral carbon nanotube network structures and their effect on the terahertz radiation detection |
Type |
Journal Article |
| Year |
2016 |
Publication |
J. Appl. Phys. |
Abbreviated Journal |
J. Appl. Phys. |
| Volume |
120 |
Issue |
4 |
Pages |
044501 (1 to 13) |
| Keywords |
carbon nanotubes, CNT detectors, plasmons |
| Abstract |
We consider the carrier transport and plasmonic phenomena in the lateral carbon nanotube (CNT) networks forming the device channel with asymmetric electrodes. One electrode is the Ohmic contact to the CNT network and the other contact is the Schottky contact. These structures can serve as detectors of the terahertz (THz) radiation. We develop the device model for collective response of the lateral CNT networks which comprise a mixture of randomly oriented semiconductor CNTs (s-CNTs) and quasi-metal CNTs (m-CNTs). The proposed model includes the concept of the collective two-dimensional (2D) plasmons in relatively dense networks of randomly oriented CNTs (CNT “felt”) and predicts the detector responsivity spectral characteristics exhibiting sharp resonant peaks at the signal frequencies corresponding to the 2D plasmonic resonances. The detection mechanism is the rectification of the ac current due the nonlinearity of the Schottky contact current-voltage characteristics under the conditions of a strong enhancement of the potential drop at this contact associated with the plasmon excitation. The detector responsivity depends on the fractions of the s- and m-CNTs. The burning of the near-contact regions of the m-CNTs or destruction of these CNTs leads to a marked increase in the responsivity in agreement with our experimental data. The resonant THz detectors with sufficiently dense lateral CNT networks can compete and surpass other THz detectors using plasmonic effects at room temperatures. |
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0021-8979 |
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no |
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Serial |
1777 |
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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. |
| Title |
Synthesis of single-walled carbon nanotube networks using monodisperse metallic nanocatalysts encapsulated in reverse micelles |
Type |
Journal Article |
| Year |
2016 |
Publication |
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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0367-598X |
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no |
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Serial |
1779 |
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| Author |
Fedorov, G.; Gayduchenko, I.; Titova, N.; Gazaliev, A.; Moskotin, M.; Kaurova, N.; Voronov, B.; Goltsman, G. |
| Title |
Carbon nanotube based schottky diodes as uncooled terahertz radiation detectors |
Type |
Journal Article |
| Year |
2018 |
Publication |
Phys. Status Solidi B |
Abbreviated Journal |
Phys. Status Solidi B |
| Volume |
255 |
Issue |
1 |
Pages |
1700227 (1 to 6) |
| Keywords |
carbon nanotube schottky diodes, CNT |
| Abstract |
Despite the intensive development of the terahertz technologies in the last decade, there is still a shortage of efficient room‐temperature radiation detectors. Carbon nanotubes (CNTs) are considered as a very promising material possessing many of the features peculiar for graphene (suppression of backscattering, high mobility, etc.) combined with a bandgap in the carrier spectrum. In this paper, we investigate the possibility to incorporate individual CNTs into devices that are similar to Schottky diodes. The latter is currently used to detect radiation with a frequency up to 50 GHz. We report results obtained with semiconducting (bandgap of about 0.5 eV) and quasi‐metallic (bandgap of few meV) single‐walled carbon nanotubes (SWNTs). Semiconducting CNTs show better performance up to 300 GHz with responsivity up to 100 V W−1, while quasi‐metallic CNTs are shown to operate up to 2.5 THz. |
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0370-1972 |
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no |
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1321 |
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