Chirality distribution and transition energies of carbon nanotubes

TL;DR

This study uses resonant Raman scattering to determine optical transition energies, chiral indices, and vibrational properties of individual carbon nanotubes, revealing systematic chiral-angle dependencies and including zig-zag tubes.

Contribution

It unambiguously assigns chiral indices to about 50 nanotubes using a third-neighbor tight-binding model, expanding understanding of nanotube optical properties.

Findings

Identified optical transition energies and Raman features for various nanotubes.

Confirmed chiral-angle dependence of Raman intensities.

Observed all chiralities, including zig-zag tubes, contrasting luminescence results.

Abstract

From resonant Raman scattering on isolated nanotubes we obtained the optical transition energies, the radial breathing mode frequency and Raman intensity of both metallic and semiconducting tubes. We unambiguously assigned the chiral index (n_1,n_2) of approximately 50 nanotubes based solely on a third-neighbor tight-binding Kataura plot and find omega_RBM=214.4cm^-1nm/d+18.7cm^-1. In contrast to luminescence experiments we observe all chiralities including zig-zag tubes. The Raman intensities have a systematic chiral-angle dependence confirming recent ab-initio calculations.