UV Raman spectroscopy of single-walled carbon nanotubes

Deep W Raman spectroscopy is emerging as a useful tool for the characteriza tion of carbon materials that has many advantages over visible Raman spectr oscopy. However, because of resonance enhancement and other effects, UV Ram an spectra are often different from visible Raman spectra. UV Raman spectra have not been reported for even some of the most widely known carbon mater ials. We report Raman spectra of single-walled carbon nanotubes (SWNTs) col lected with deep ultraviolet (4.8 eV) laser excitation. There are significa nt differences between the deep UV and the visible Raman spectrum of SWNTs for the graphitic "G" modes and "disorder-induced" "D" modes, which are com mon to a wide range of forms of carbon. Furthermore, only semiconducting tu bes are observed in the UV Raman spectrum, which is not consistent with an expected resonance enhancement of the scattering from metallic tubes at 4.8 eV.