Two-dimensional plasmons in lateral carbon nanotube network structures and their effect on the terahertz radiation detection

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 another contact is the Schottky contact. These structures can serve as detectors of the terahertz (THz) radiation. We develop the device model for 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 two-dimensional plasmons in relatively dense networks of randomly oriented CNTs (CNT "felt") and predicts the detector responsivity spectral characteristics. 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. We demonstrate that the excitation of the two-dimensional plasmons by incoming THz radiation the detector responsivity can induce sharp resonant peaks of the detector responsivity at the signal frequencies corresponding to the plasmonic resonances. 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.