The Influence of Catalyst's Oxidation Degree on Carbon Nanotube Growth as a Substrate-Independent Parameter

The final oxidation state of iron particles, used as catalysts for the growth by chemical vapor deposition of carbon nanotubes, was investigated by means of in situ photoelectron spectroscopy. Although the chemical evolution of the catalyst during the process is known to depend strongly on the nature of the substrate, we could address nanotube growth from metallic and fully oxidized particles grown onto the same type of substrate (Al 2 O 3 ). While oxide particles promoted carbon nanotube growth efficiently, metallic particles of roughly the same size, known to be active onto other kinds of substrates, showed a very poor performance.