Direct growth of vertically aligned carbon nanotubes on stainless steel by plasma enhanced chemical vapor deposition

Abstract Applications such as energy storage and field emission devices demand direct growth of vertically aligned carbon nanotube (VACNT) arrays on conducting metal substrates, which has remained a challenge for a long time. Here, we report a controlled growth of VACNT arrays on a stainless steel (SS) substrate via dc plasma enhanced chemical vapor deposition without the addition of a metal catalyst layer. TEM and AFM examinations revealed the occurrence of nano-hills formed on the SS surface during heating process in an NH3 environment. This is a key step for uniform growth of VACNTs. The VACNTs have uniform length and diameter, good alignment, and uniform coverage over the substrate surface, superior to reported results. The particle on the tip of most of the VACNTs was found to be single crystalline Fe metal, although a few other VACNTs were found to have an alloy of Fe, Ni, Mn, and Cr at the tips. This highlights the dominating catalytic behavior of Fe over Ni, Cr, and Mn, which are the elemental composition of the nano-hills. The high quality VACNTs may find unique applications such as electron field emitters and dense nanoscale anode materials for lithium ion batteries.