Single- and double-resonance RamanG-band processes in carbon nanotubes

This work reports Raman spectroscopy measurements from single wall carbon nanotubes (SWNTs) addressing the nature of the $G$-band resonance Raman spectra. Experimental results on different samples are presented, i.e., aligned and misaligned SWNT samples, as well as isolated and bundled SWNTs. It is shown that the Raman spectra from nondefective SWNTs, both isolated and bundled, are composed of strong first-order single resonance Raman features. Defective materials, however, are found to exhibit lower intensity spectra with contributions from both single resonance and defect-induced double resonance features.