DENSITY OF PARTICLES ON CENTER AXIS OF ARC FRAME FOR GENERATION OF CARBON NANOTUBES

This study analyzes the growth process of nanotubes. Using helium as t he inert gas, an are discharge plasma is generated between carbon elec trodes, and the spatial distribution of the emission and its dependenc y on the gas pressure are examined. Based on the emission intensities of C+ at wavelengths of 657.8 and 723.6 nm, the plasma temperature is determined by two-spectral line intensity comparison. It is seen that the plasma temperature rises from the anode to the cathode and falls w ith increase of the gas pressure. The temperature near the cathode, wh ere the nanotubes grow, is between 5500 and 6000 K. Based on the parti cle density-temperature relation derived by a theoretical calculation, the neighborhood of the cathode, where the nanotubes grow, seems most ly occupied by the monomer C. The particle density, which is derived f rom the emission intensity and the temperature distribution, decreases from the anode to the cathode, indicating that C is transported by di ffusion from the anode toward the cathode. The diffusion rate of C nea r the cathode increases with increase of the gas pressure, which enhan ces the transport of C toward the cathode. The particle density of Cderived by the same method decreases from the anode to the cathode, in dicating that there exists a diffusion in addition to the drift from t he anode to the cathode. The particle density increases with gas press ure. This suggests that the density of the carbon monomer and its tran sport are the important factors for the growth of nanotubes in an are discharge. (C) 1998 Scripta Technica.