Analyses of early stages of vertically aligned carbon nanotube growth by plasma-enhanced chemical vapor deposition

The pretreatment and early stages of aligned carbon nanotube (CNT) growth by hot-filament-assisted plasmas-enhanced chemical vapor deposition have been analyzed by scanning electron microscopy, X-ray photoelectron spectroscopy, and in situ ellipsometry. It was found that the effect of pretreatment on the aligned growth is due to the formation of finer catalyst particles through sputtering by ions accelerated in a sheath electric field. It was also found that the optimum growth temperature affects the aligned growth of CNTs. Poorly aligned growth at the higher temperatures is due to the insufficient formation of finer catalyst particles under the competition with coalescence. To align the growth of CNTs, fine catalyst particles smaller than a certain size are required.