Intersubband Plasmon Observation in Electrochemically Gated Carbon Nanotube Films

Abstract

Intersubband plasmon excited in heavily doped carbon nanotubes by the external electromagnetic field in the near-infrared range is known to be sensitive to both the nanotube diameter and Fermi level shift. This work provides experimental results on the intersubband plasmon frequency measured as a function of gating voltage in single-walled carbon nanotube (SWCNT) thin films. We have explored SWCNTs with three mean diameters of 1.0, 1.4, and 2.0 nm being electrochemically gated in the ionic liquid. It is demonstrated that the plasmon frequency could be tuned in the range from 0.8 to 1.5 eV while the Fermi level was shifted up to 1.2 eV by using the electrochemical gating. Indeed, we have observed the theoretically predicted intersubband plasmon and discussed the influence of tubes bundling on the plasmon frequency shift with respect to the theoretical prediction for isolated SWCNTs. The increase of the bundle size red-shifts the plasmon frequency similar to the increase of the nanotube diameter.

Densification of single-walled carbon nanotube films: Mesoscopic distinct element method simulations and experimental validation

“…Significant densification can be achieved by the drop-cast volatile liquid processing of the pristine films. 45 As it can be seen in the SEM image shown in Fig. 3(e), on the few μm scale, such densified films preserve the branching characteristic observed earlier in pristine films.…”

“…As such, the number of CNTs in these "medium" bundles can only be estimated based on the measured bundle thickness and the mean diameter 2r CNT of individual CNTs. For example, an ∼10 nm bundle with a hexagonal closed-packed 2r CNT ¼ 2:2 nm single-walled CNTs 45 would contain about 14 CNTs. Figure 3(d) details the zipping of three "medium" bundles into a larger bundle.…”

Highly efficient bilateral doping of single-walled carbon nanotubes

“…24 Such doping effect is manifested at UV-vis-NIR transmittance spectra (Figure 1b), leading to the removal of S 11 , S 22, and M 11 peaks and the appearance of a new peak that corresponds to the intersubband plasmon of nanotubes appearing when excitonic levels are fully saturated with charge carriers. 27,28 These data prove that p-doping caused an efficient downshift of Fermi level favored by the HAuCl 4 treatment.…”

A Review of the Terahertz Conductivity and Photoconductivity of Carbon Nanotubes and Heteronanotubes

“…In our review, we focus on intrasubband transitions and show that these transitions are sensitive to the length of CNTs, rather than to their diameter, as is the case for intersubband plasmons. [127][128][129] The optical absorption is also suppressed when the incident light is perpendicular to the CNT axis due to the depolarization effect, also called the antenna effect or screening effect. The physical explanation of this effect was presented in ref.…”