Raman investigation of singlewalled carbon nanotubes

Singlewalled carbon nanotubes (SWNT's) prepared by the electric arc method are characterized by means of spectroscopic techniques, mainly Transmission Electron Microscopy and resonance Raman scattering. TEM observations reveal the existence of nickel particles embedded in an amorphous carbon matrix, but also a large concentration of SWNT's, whose average diameter can be estimated to be near 1.3 nm, arranged in bundles. Raman spectra recorded on the same samples exhibit several features, mainly consisting of two groups. On one hand, in the high frequency region, several bands are observed in the range 1500 - 1600 cm(-1), corresponding to a splitting of the E(2g2) vibrational mode of graphite. On the other hand, several components are recorded between 150 and 240 cm(-1), reflecting a distribution in the diameter of the SWNT's. A systematic study of the "collaret", from which samples are extracted, is also presented.