RESUMO
Single wall carbon nanotubes (SWNTs) were synthesized by electric are discharge method with a mixture of nickel and yttrium as catalysts. The examination results of scanning electronic microscope and transmission electronic microscope indicate that the yield of SWNTs in the sample were high. SWNTs have been investigated by Raman scattering techniques with excitation wavelengths in the range of 514.5 to 782.0 nm. We have observed some differences in the frequencies and intensities of the radial breathing modes. The electronic density of states of SWNTs was calculated using the Brillouin zone folding. A graphical method was proposed for assigning Raman peaks of the radial breathing modes (RMB) based on the data of diameters, RBM frequencies and electronic density of states of SWNTs. The radial breathing modes on SWNTs are assigned. The results indicate that the diameter distribution of SWNTs is in the range of 0.79-1.76 nm, and the SWNTs with diameter 1.45 nm are in the majority. The metallic and semiconductor tubes are all present in the sample.