Possible Growth Region of Single-Walled Carbon Nanotube in CVD Synthesis on the CHO Components Diagram

Considering the massive-scale synthesis of single-walled carbon nanotube (SWCNT), chemical vapor deposition has become a standard process for synthesizing CNTs. In most of these processes, oxygen and hydrogen atoms were included originally or added later; and they are expected to have important roles such that they helped in the removal of amorphous carbon and prevented SWCNTs from containing metal particles. However, whole perspectives for suitable carbon source or ideal balance among carbon, hydrogen, and oxygen have not been reported. We examined a variety of raw materials in our newly developed round-trip-type vacuum furnace in order to determine whether they could be used to synthesize a carbon nanotube. We used Raman spectroscopy for evaluation, and plotted the component ratios of effective and ineffective materials on a C-H-O ternary diagram. Consequently, it is clear that the growth region should satisfy the equation O < C < (H + O) in molar ratio.