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Bandurin, D. A., Gayduchenko, I., Cao, Y., Moskotin, M., Principi, A., Grigorieva, I. V., et al. (2018). Dual origin of room temperature sub-terahertz photoresponse in graphene field effect transistors. Appl. Phys. Lett., 112(14), 141101 (1 to 5).
Abstract: Graphene is considered as a promising platform for detectors of high-frequency radiation up to the terahertz (THz) range due to its superior electron mobility. Previously, it has been shown that graphene field effect transistors (FETs) exhibit room temperature broadband photoresponse to incoming THz radiation, thanks to the thermoelectric and/or plasma wave rectification. Both effects exhibit similar functional dependences on the gate voltage, and therefore, it was difficult to disentangle these contributions in previous studies. In this letter, we report on combined experimental and theoretical studies of sub-THz response in graphene field-effect transistors analyzed at different temperatures. This temperature-dependent study allowed us to reveal the role of the photo-thermoelectric effect, p-n junction rectification, and plasmonic rectification in the sub-THz photoresponse of graphene FETs.
D.A.B. acknowledges the Leverhulme Trust for financial support. The work of D.S. was supported by Grant No. 16-19-10557 of the Russian Scientific Foundation (theoretical model). G.F., I.G., M.M., and G.G. acknowledge the Russian Science Foundation [Grant No. 14-19-01308 (MIET, cryostat upgrade) and Grant No. 17-72-30036, (MSPU, photoresponse measurements), the Ministry of Education and Science of the Russian Federation (Contract No. 14.B25.31.0007 (device fabrication) and Task No. 3.7328.2017/LS (NEP analyses)] and the Russian Foundation for Basic Research [Grant No. 15-02-07841 (device design)]. The authors are grateful to Professor M. S. Shur for helpful discussions.
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Bandurin, D. A., Svintsov, D., Gayduchenko, I., Xu, S. G., Principi, A., Moskotin, M., et al. (2018). Resonant terahertz detection using graphene plasmons. Nat. Commun., 9, 5392 (1 to 8).
Abstract: Plasmons, collective oscillations of electron systems, can efficiently couple light and electric current, and thus can be used to create sub-wavelength photodetectors, radiation mixers, and on-chip spectrometers. Despite considerable effort, it has proven challenging to implement plasmonic devices operating at terahertz frequencies. The material capable to meet this challenge is graphene as it supports long-lived electrically tunable plasmons. Here we demonstrate plasmon-assisted resonant detection of terahertz radiation by antenna-coupled graphene transistors that act as both plasmonic Fabry-Perot cavities and rectifying elements. By varying the plasmon velocity using gate voltage, we tune our detectors between multiple resonant modes and exploit this functionality to measure plasmon wavelength and lifetime in bilayer graphene as well as to probe collective modes in its moire minibands. Our devices offer a convenient tool for further plasmonic research that is often exceedingly difficult under non-ambient conditions (e.g. cryogenic temperatures) and promise a viable route for various photonic applications.
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Belosevich, V. V., Gayduchenko, I. A., Titova, N. A., Zhukova, E. S., Goltsman, G. N., Fedorov, G. E., et al. (2018). Response of carbon nanotube film transistor to the THz radiation. In EPJ Web Conf. (Vol. 195, 05012 (1 to 2)).
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Dube, I., Jiménez, D., Fedorov, G., Boyd, A., Gayduchenko, I., Paranjape, M., et al. (2015). Understanding the electrical response and sensing mechanism of carbon-nanotube-based gas sensors. Carbon, 87, 330–337.
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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Fedorov, G., Gayduchenko, I., Titova, N., Gazaliev, A., Moskotin, M., Kaurova, N., et al. (2018). Carbon nanotube based schottky diodes as uncooled terahertz radiation detectors. Phys. Status Solidi B, 255(1), 1700227 (1 to 6).
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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