Structural modification of single-walled carbon nanotube induced by X-ray irradiation and subsequent annealing studied by Raman scattering spectroscopy in radial breathing mode

The formation of X-ray-induced defects changes the spectral shape of the radial breathing mode (RBM) and defect-induced mode (D band) in the Raman spectra of single-walled carbon nanotubes (SWNTs). X-ray-induced defects have been found to be annealed by thermal treatment, indicating that they are Frenkel pairs (vacancy and interstitial pairs). We found that the spectral shape of RBM is not entirely recovered after post-irradiation annealing. The temperatures for the complete annealing of X-ray-induced defects were within the range of 200–600 °C depending on the tube geometry. From these results, we suggest that the stability of X-ray-induced defects depends on the tube geometry and that the combination of X-ray irradiation and post-irradiation annealing causes a chirality change in SWNTs.