The radial breathing mode in the Raman spectrum of 13C isotope enriched single walled carbon nanotubes is inhomogeneously broadened due to the random distribution of isotopes. We study this effect theoretically using density functional theory within the local density approximation and compare the result with experiments on isotope engineered double walled carbon nanotubes in which the inner tubes were grown from a mixture of 13C enriched fullerenes and natural fullerenes. As explained by the calculations, this synthesis procedure leads to an increased inhomogeneity compared to a case when only enriched fullerenes are used. The good agreement between the measurements and calculations shows the absence of carbon diffusion along the tube axis during inner tube growth, and presents a strong support of the theory that inner tube growth is governed by Stone-Wales transformations following the interconnection of fullerenes.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics