Raman bands of double‐wall carbon nanotubes: comparison with single‐ and triple‐wall carbon nanotubes, and influence of annealing and electron irradiation

Abstract

Abstract We compare the G and G′ 2D bands of single‐, double‐ and triple‐wall carbon nanotubes (CNTs). We observe that the band shape is sensitive to the number of walls of the CNTs. For single‐wall carbon nanotubes (SWCNTs), the G band is composed of two distinct contributions G+ and G−, while the G band for double‐wall nanotubes is composed of one band with two main contributions from the inner and the outer tube. The G′ 2D band can be fitted with one Lorentzian for single‐wall tubes, while two distinct contributions are observed for double‐wall carbon nanotubes (DWCNTs). Considerable variations of the G′ 2D band are found with similar first order Raman spectra. Annealing influences the D‐ and RBM‐band intensities. Electron irradiation has the effect of decreasing the G‐ and D‐band wavenumbers but does not enhance the D‐band intensity considerably. The down‐shifts of the G‐ and D‐band wavenumbers are correlated and are the same for two excitation wavelengths. This is consistent with the scattering of phonons around the K‐point. Copyright © 2007 John Wiley & Sons, Ltd.