Electron energy-loss spectra of carbon nanotubes

Carbon nanotubes were investigated by means of electron energy-loss spectroscopy. Two peaks due to the n plasmon and the π + σ plasmon were observed. The energy of the π + σplasmon 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 n 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.