Intensity Ratio of Resonant Raman Modes for (n,m) Enriched Semiconducting Carbon Nanotubes

Abstract

Relative intensities of resonant Raman spectral features, specifically the radial breathing mode (RBM) and G modes, of eleven, chirality-enriched, single-wall carbon nanotube (SWCNT) species were established under second-order optical transition excitation. The results demonstrate an under-recognized complexity in the evaluation of Raman spectra for the assignment of (n,m) population distributions in agreement with theory predicted by a symmetry-adapted nonorthogonal tight-binding model.[1] Strong chiral angle and mod dependencies affect the intensity ratio of the RBM to G modes. Furthermore, we report five additional values for chirality dependent G+ and G- Raman peak positions and intensity ratios extending the available data to cover more of the smaller diameter regime by including the first (5,4) second-order, resonance Raman spectra.[2] Together, the Raman spectral library is demonstrated to be sufficient for decoupling multiple species viaa spectral fitting process, and enables fundamental characterization even in mixed chiral population samples.