Chiral Index Dependence of the G+ and G- RamanModes in Semiconducting Carbon Nanotubes
Ming Zheng, Xiaomin X. Tu, Hagen Telg, Stephen K. Doorn, Juan Duque
Raman spectroscopy on the radial breathing mode is a common tool to determine the diameter d or chiral indices (n;m) of single walled carbon nanotubes. In this work we presentan alternative technique to determine d and (n;m) based on the high-energy G mode. From resonant Raman scattering experiments on 14 highly purified single chirality (n;m) samples we obtain the diameter, chiral angle and family dependence of the G and G+ peak position. Considering theoretical predictions we discuss the origin of these dependences with respect to rehybridization of the carbon orbitals, confinement, and electron-electron interactions. The relative Raman intensities of the two peaks have a systematic chiral-angle dependence in agreement with theories considering the symmetry of nanotubes and the associated phonons.