Diffusion - and reaction - limited growth of carbon nanotube forests

摘要

We present a systematic study of the temperature and pressure dependence of the growth rate of vertically aligned small diameter (single- and few-walled) carbon nanotube forests grown by thermal chemical vapor deposition over the temperature range 560-800 ～C and 10~(-5) to 14 mbar partial pressure range, using acetylene as the feedstock and Al_2O_3- supported Fe nanoparticles as the catalyst. We observe a pressure dependence of P~(0.6) and activation energies of < 1 eV. We interpret this as a growth rate limited by carbon diffusion in the catalyst, preceded by a pre-equilibrium of acetylene dissociation on the catalyst surface. The carbon nanotube forest growth was recorded by high-resolution real-time optical imaging.