Effect of nanoparticle density on narrow diameter distribution of carbon nanotubes and particle evolution during chemical vapor deposition growth

Single-walled carbon nanotubes (SWNTs) were synthesized by chemical vapor deposition (CVD) using catalytic nanoparticles both on the substrates and above the substrates in order to investigate the effect of nanoparticle density on diameter-controlled SWNT growth. As the density of the catalytic nanoparticles increased, tube-diameter distribution broadened and the diameter itself also increased. SWNTs observed in this study were grown by the base-growth mechanism and their diameters were much smaller than those of the nanoparticles. Based on elaborate diameter measurements, we reasonably conjecture that the time evolution of catalytic nanoparticles during CVD growth can explain these large size differences. (c) 2005 American Institute of Physics.