Identification of the conducting category of individual carbon nanotubes from Stokes and anti-Stokes Raman scattering

Raman spectra of radial breathing modes (RBM's) of single-walled carbon nanotubes (SWNT's) are re ported to exhibit a different resonantly enhanced behavior between the Stokes and anti-Stokes Raman-scattering components, from which we determine the electronic transition energy of individual SWNT's that is involved in the resonant process. By comparing the measured electronic transition energy with the theoretical energy separations between singularities in the one-dimensional density of electronic states for metallic or semiconducting SWNT's, the conducting category of observed SWNT's is identified. Moreover, we find that the relative intensity of each RBM does not reflect the proportion of a particular SWNT due to the coexistence of resonant and nonresonant Raman-scattering processes for different diametric SWNT's.