Carbon nanotubes by plasma-enhanced chemical vapor deposition

This paper presents the growth of vertically aligned carbon nanotubes by plasma-enhanced chemical vapor deposition (PECVD) using Ni catalyst and C2H2/NH3 feedstock. The role of plasma in aligning the carbon nanotubes during growth is investigated both experimentally and computationally, confirming that the field in the plasma sheath causes the nanotubes to be aligned. Experiments using a plasma analyzer show that C2H2 is the dominant precursor for carbon nanotube growth. The role of NH3 in the plasma chemistry is also investigated, and experimental results show how the interaction between NH3 and the C2H2 carbon feedstock in the gas phase explains the structural variation in deposited nanotubes for differing gas ratios. The effects of varying the plasma power during deposition on nanotube growth rate is also explored. Finally, the role of endothermic ion-molecule reactions in the plasma sheath is investigated by comparing measured data with simulation results.