Vertically-Aligned Carbon Nanotube Growth Using Closely Packed Iron Oxide Nanoparticles
A high density of catalyst nanoparticles is essential to grow vertically-aligned carbon nanotubes (CNTs). We have grown vertically-aligned CNTs on silicon, thermally-oxidized silicon as well as alumina substrates by arranging iron oxide nanoparticles in two-dimensional close-packed structure with a density of 1.5 × 1012 cm-2. Use of toluene as solvent together with uniform diameter oxide nanoparticles is the key to obtain the close-packed configuration. Even after Ar/H2 annealing treatment, the density of the iron oxide nanoparticles remained as 7.0- 9.5 × 1011 cm - 2. We synthesized submillimeter-order heights of multi-walled CNTs on each substrate using acetylene as a carbon source for chemical vapor deposition.