We investigate the growth mechanisms of single wall carbon nanotubes (SWNTs) produced by the solar method as a function of the nature of catalysts and the temperature variation in the condensing area. The Raman spectra clearly show differences in SWNT diameters induced by the change of catalyst whereas TEM pictures enhance the change of both length and diameter of the bundles. All the results are explained considering that the formation temperature range of SWNTs is the key parameter related to the target sublimation temperature and to the eutectic temperature of the binary phase diagram.