It was recalled that diffusion of carbon was the crucial step in the chemical vapour deposition growth of carbon nanotubes on metal nanoparticles. Using first principles techniques, the binding and diffusion of carbon atoms and dimers on late transition (Ni, Pd, Pt) and coinage (Cu, Ag, Au) metal catalysts was modelled. Various diffusion mechanisms were considered, including both surface and sub-surface channels, finding the lowest activation barriers for carbon adatoms on nanoparticles of coinage metals. For these metals, the calculations further showed that the diffusion was restricted to the nanoparticle surface when diatomic carbon was initially obtained from the decomposition of the precursor gas. In combination with the results for the binding of carbon nanotube fragments to metal nanoparticles, it was concluded that coinage metal catalysts, in particular Cu, favoured the chemical vapour deposition growth of carbon nanotubes at low temperatures and with narrow chirality distributions.

Carbon Diffusion in CVD Growth of Carbon Nanotubes on Metal Nanoparticles. O.V.Yazyev, A.Pasquarello: Physica Status Solidi B, 2008, 245[10], 2185-8