Electron Energy-Loss Spectra of Carbon Nanotubes

Abstract

Carbon nanotubes were investigated by means of electron energy-loss spectroscopy. Two peaks due to the π plasmon and the π+σ plasmon were observed. The energy of the π+σ plasmon peaks varied from 22.0 eV to 24.5 eV, which roughly agrees with the average plasmon energy of graphite. A shoulder due to single electron excitations was observed at 13 eV, which was not observed in graphite. There were two kinds of nanotubes which exhibited their respective π plasmon peaks at 5.2 eV and 6.4 eV. The peaks in the dielectric function obtained by Kramers-Kronig analysis of the spectra were broader than those of graphite probably due to the curving of the graphitic sheets.

Optical absorption and energy-loss spectra of aligned carbon nanotubes

“…1, as obtained from either Eqs. (6) and (7) with ε (ω) = ε ⊥ (ω) or from Eqs. (17) and (18), and for various values of the ratio between the inner and outer radii of the cylinders: ρ = 0 (solid line), ρ = 0.2 (dotted line), ρ = 0.4 (short-dashed line), ρ = 0.6 (long-dashed line), and ρ = 0.8 (solid line).…”

Electronic and optical properties of single-walled carbon nanotubes under a uniform transverse electric field: A first-principles study

“…Our recent firstprinciples studies suggested that the metallic band energy dispersion relation of armchair CNT indeed develops multivalleys at the Fermi level, which can lead to conduction amplification under a transverse electric field. 5 The optical properties of CNTs have been investigated experimentally by optical absorption spectroscopy, 6,7 by high-resolution electron-energy-loss spectroscopy in transmission, 8 by reflectivity measurements, 9 and also by spectrofluorimetric measurements. 10 Calculations of the optical properties of CNTs have been reported intensively by -band model, 11 modified tight-binding ͑TB͒ model, 12 all-valence TB models, 13,14 and ab initio models 15 showing that the absorption spectra exhibit rich characteristic peaks due to the onedimensional Van Hove singularities.…”

Ab initiostudy of the dielectric response of crystalline ropes of metallic single-walled carbon nanotubes: Tube-diameter and helicity effects

“…5 Electron spectroscopies 6,7 are powerful experimental tools which can probe the internal electronic structure of the tubes. In particular, electron energy-loss spectroscopy ͑EELS͒ has been recently employed to analyze the dielectric response of isolated carbon nanotubes 2,8 as well as of bulk polycrystalline samples of nanotubes. [9][10][11][12] By theoretical means, the existing research on the dielectric response of carbon nanotubes falls under three categories: ͑a͒ Model calculations 13 based on an electron-gas treatment of the response; ͑b͒ tight-binding calculations 14 based on a -electron Hamiltonian.…”