Effects of N₂on the Growth of Multiwalled Carbon Nanotubes Synthesized by Plasma-Enhanced Chemical Vapor Deposition

We have investigated the role of N 2 in the synthesis of carbon nanotubes (CNTs) by dc hot-filament plasma-enhanced chemical vapor deposition. An NH 3 and C 2 H 2 gas mixture with a ratio of 4:1 was used as a precursor for the synthesis of CNTs on nickel-coated TiN/Si (100) substrates. N 2 gas was introduced at a flow rate of 30–120 sccm with the precursor. The structure and composition of CNTs synthesized with/without N 2 were investigated by scanning electron microscopy, transmission electron microscopy, X-ray photoemission spectroscopy (XPS), and Raman spectroscopy. The multiwalled carbon nanotubes (MWCNTs) synthesized with N 2 were 2–5 times longer than those synthesized without N 2 , and the morphology of the MWCNTs was improved. An XPS core level spectrum shows that nitrogen is in the CN X and C–NH 2 forms.