Horizontally-aligned single-walled carbon nanotubes on sapphire.

Recently, we discovered the horizontally-aligned growth of single-walled carbon nanotubes (SWCNTs) on R- and A-plane sapphire substrates, which we call "atomic arrangement-programmed growth (AAP growth)". This is a unique method because the growth direction of SWCNTs is determined by the crystallographic direction of the sapphire surface. In this paper, we report on the characterization of the aligned SWCNTs by polarized Raman and electron transport measurements, and on the effect of the step/terrace structure formed on sapphire surface.

Unidirectional growth of single-walled carbon nanotubes.

Unidirectional growth of single-walled carbon nanotubes (SWNTs) was achieved using the patterned Co-Mo salt catalyst on the r-plane sapphire substrate. This is in marked contrast with the SWNTs grown on an a-plane sapphire and ST-cut quartz, on which the SWNTs grew bidirectionally. This new growth mode is not dependent on the gas flow and attributed to the asymmetric surface atomic arrangement of the sapphire surface.

Crystal plane dependent growth of aligned single-walled carbon nanotubes on sapphire.

On single-crystal substrates, such as sapphire (alpha-Al 2O 3) and quartz (SiO 2), single-walled carbon nanotubes (SWNTs) align along specific crystallographic axes of the crystal, indicating that the SWNT growth is influenced by the crystal surface. Here, we show that not only the orientation, but also the diameter and chirality of SWNTs are affected by the crystal plane of the sapphire substrate. The aligned SWNTs grown on the A- and R-planes of sapphire have narrower diameter distributions than randomly oriented tubes produced on the C-plane sapphire and amorphous SiO 2.

Microreactor utilizing a vertically-aligned carbon nanotube array grown inside the channels.

We have fabricated a microreactor incorporating vertically-aligned carbon nanotubes supporting Pt nanoparticles and found that the presence of aligned nanotubes significantly enhances the catalytic reaction and extends the catalyst lifetime as compared with conventional microreactors using a Pt metal film or Pt nanoparticles directly deposited on the channel walls.