Influence of Plasma State on the Structural Property of Vertically Oriented Carbon Nanotubes Grown by RF Plasma-Enhanced Chemical Vapor Deposition

We investigated the correlation between plasma state and structural property in the growth of vertically oriented carbon nanotube (V-CNT) by RF plasma-enhanced chemical vapor deposition (RF-CVD) using pure CH4. The plasma diagnostics in the RF-CVD was performed as a function of RF power using optical emission spectroscopy and self-bias (Vdc) measurement. The structural properties of the grown V-CNT were significantly correlated with the fractions of CH radicals, H atoms or radicals, and Vdc, which were increased with increasing RF power. It was suggested that during V-CNT growth, the H species act as etchants, while the CH radical acts as a precursor of the growth. These antagonistic factors influenced the structural properties of V-CNT, yielding an optimum RF power for the growth of V-CNTs with good crystallinity.