Optical emission spectroscopy of arc flame plasma for generation of carbonnanotubes

Spatial distributions of plasma temperature and densities of carbon species in DC are discharge for generating carbon nanotubes have been investigated by measuring the spatial distributions of optical emission spectra as a fu nction of pressure, current density for are discharge, and cooling rare of the cathode. It is found that the nanotube yield is high when the temperatu re at the axial center of the cathode is higher than 6000 K so that the dom inant species is in the are flame carbon monomer. The potential drop at the cathode sheath, calculated from the model proposed by Rethfeld et al. [J. Phys. D 29 (1996) 121], is high for the high nanotube yield in comparison t o that under the low yield conditions.