Anisotropy in the Phonon Dispersion Relations of Graphite and Carbon Nanotubes Measured by Raman Spectroscopy

The possible semiconducting device use of single wall carbon nanotubes (SWNTs) requires a technique for the determination of the exact structure of the nanotubes assembled in the device configuration. Raman spectroscopy has been established as a precise and non-destructive tool for the characterization of graphitic nanostructures. Double resonance theory, which is used to explain the dispersive nature of the Raman bands, has attracted much attention for its potential use for the characterization of the electronic and phonon spectra of these nanostructures. Dispersive features in the Raman spectra of low dimensional graphitic materials, such as carbon nanotubes, can be used to measure directly the anisotropy , or the trigonal warping effect, in the phonon dispersion relations about the hexagonal corner of the Brillouin zone (BZ) of graphite.