Aligned growth of single-walled and double-walled carbon nanotube films by control of catalyst preparation

The synthesis of dense, aligned carbon nanotubes (CNTs) on a Si substrate was achieved by microwave plasma-enhanced chemical vapor deposition. Catalyst nanoparticles were prepared on the Si substrate without a buffer layer, by pulsed arc plasma deposition with the alternate use of Co and Ti electrodes. Ti mixed with Co nanoparticles prevents the formation of Co silicides during substrate heating, enabling the control of Co catalyst nanoparticle size at approximately 1-2 nm. By changing the numbers of cumulative Co nanoparticles on the Si substrate, the fabrication of single-walled CNTs (SWNTs) and double-walled CNTs (DWNTs) can be controlled. In addition, catalyst nanoparticles were patterned using a lift-off method, and the area-selective growth of vertical SWNTs forming organized CNT microstructures was demonstrated.