Optical absorption and resonance Raman scattering of carbon nanotubes

Abstract

Four kinds of single-walled carbon nanotubes (SWNTs) with different diameter distributions were synthesized using NiY, NiCo, Ni and RhPd catalysts. Optical absorption and resonance Raman spectra were measured. For all the samples, three large absorption peaks were observed from the infrared to visible region. From the band calculation, it was found that they could be explained by the optical transitions between mirror image spikes in density of states caused by the one-dimensional van Hove singularities. Lower two peaks are originating from the semiconductor phases and the third one is from the metallic phases. In the Raman spectra, indeed, broad and asymmetric Fano line shape was observed when the excitation was at the optical transition of metallic SWNTs. Preliminary results about resonance Raman scattering of multiwall carbon nanotubes that have small core diameter and of Br2 doped SWNTs are shown.