Observations of the D-band feature in the Raman spectra of carbon nanotubes

We examine the behavior of the D-band feature in the Raman spectra of single-walled carbon nanotube (SWNT) bundles, observed between 1250 and $1450\hspace{0.5em}{\mathrm{cm}}^{-1},$ as a function of the laser excitation energy. We used three SWNT samples with different diameters, and show that the D-band behavior of SWNTs differs from ${\mathrm{sp}}^2$ carbons, depending on whether the SWNTs are metallic or semiconducting, and shows a frequency ${\omega }_D$ that is dependent on nanotube diameter.