A plasma enhanced chemical vapor deposition process to achieve branched carbon nanotubes

Vertically aligned carbon nanotubes (CNTs) have been grown on silicon substrates using nickel as the catalyst layer, acetylene as the carbon source, and hydrogen as the carrier gas. The quality of the CNTs has been examined using transmission and scanning electron microscopy and a tip-growth mechanism with an inner tube diameter of 5–8 nm was observed. The effect of plasma hydrogenation as a post-growth treatment was shown to lead to total or partial removal of the nickel seeds from the CNT tips. Using sequential hydrogenation and growth, it has been possible to achieve tree-like nanostructures.