Possible role of charge transport in enhanced carbon nanotube growth

We consider the role of electric fields during metal-catalysed thermal chemical vapour deposition growth of carbon nanotubes and show that enhanced growth occurs from a negatively biased electrode. An electric field, applied externally to the growing tubes and/or generated as a result of electron emission or self-biasing, may strongly affect the carbon supply through the catalyst nanoparticle, enhancing the growth rate. Different aspects of the growth process are analysed: the nature of the nanoparticle catalysis, carbon dissolution kinetics, electron emission from the nanotube tips, charge transport in the nanotube–catalytic nanoparticle system and carbon drift and diffusion through the catalyst under the action of the electric field. A fundamental tenet for modelling of charge-transport dynamics during the nanotube growth process is proposed. PACS 81.07.De; 81.15.Gh