Size dependent characteristics of single wall carbon nanotubes

Raman scattering by the phonon system is studied on single-wall nanotubes with diameters 1.1 nm and 1.3 nm. Spectra show multiple splittings in the Raman peak of optical phonon at 1580 cm−1 corresponding to E2g mode of graphite. The magnitude of splitting is larger for tubes of smaller diameter. The splittings come from the fact that the nanotube has a cyclic symmetry along the circumference direction. Our result shows direct evidence of size dependence in the properties of nanotubes.