Optical and Terahertz Properties of Electrochemically Doped Aligned Carbon Nanotubes
Egor A. Chepurov1, Aleksandr S. Marakulin1, Stanislav Colar1,2, Maksim I. Paukov1, Ksenia V. Shevyakova1,2, Artur R. Ishteev3, Oksana V. Shapovalova3, Gennady A. Komandin4, Aleksey V. Arsenin1, Dmitry V. Krasnikov5, Alexander I. Chernov1,2, Maria G. Burdanova1; 1Moscow Institute of Physics and Technology (National Research University), Dolgoprudny, Russia; 2Russian Quantum Center, Moscow, Russia; 3N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, Moscow, Russia; 4Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia; 5Skolkovo Institute of Science and Technology, Moscow, Russia
Abstract
Aligned carbon nanotube (CNT) films exhibit a pronounced polarization-dependent optical and terahertz (THz) response, making them promising for polarization-sensitive photonic and optoelectronic applications. Ionic-liquid-based electrochemical doping enables reversible modification of the carrier density and electrical conductivity of CNT films without requiring structural modification of the active layer. In this work, the optical and THz response of electrochemically doped aligned multi-walled carbon nanotube (MWCNT) films was investigated, with emphasis on voltage-controlled THz transmission.
The films were characterized by polarization-dependent transmission measurements and transmission electron microscopy. A six-layer aligned MWCNT film was selected as the active electrode because it provided a suitable balance between THz attenuation and transmitted signal strength. The orientational order parameter was approximately 0.67, indicating a high degree of macroscopic alignment. Electron microscopy confirmed that the nanotubes were multi-walled, with typical diameters of 10–15 nm.
An electrochemical cell incorporating the aligned MWCNT film and the ionic liquid [bmim][NTf₂] was fabricated and studied by terahertz time-domain spectroscopy under applied voltages ranging from −3 to +3 V. The transmission response was strongly polarization-dependent. The largest voltage-induced change was observed when the incident THz electric field was polarized parallel to the CNT alignment direction. At 0.7 THz, the relative change in transmitted field amplitude reached approximately 45%, corresponding to an intensity modulation depth of about 70%. Electrochemical doping also modified the polarization extinction ratio and THz shielding effectiveness. These results demonstrate the potential of ionic-liquid-gated aligned MWCNT films as active elements for THz amplitude modulation, polarization control, and tunable electromagnetic shielding.
Speaker
Chepurov Egor
Center for Photonics and 2D Materials, MIPT, Phystech
Russia
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