ATOMIC HYDROGEN-DRIVEN SIZE CONTROL OF CATALYTIC NANOPARTICLES FOR SINGLE-WALLED CARBON NANOTUBE GROWTH

Abstract

The effects of an atomic hydrogen (H(at)) pretreatment of the catalyst layer on the low temperature growth of single-walled carbon nanotubes (SWCNTs) have been investigated using a modified catalytic chemical vapor deposition system. Well-defined and isolated individual Fe nanoparticles as a catalyst are successfully formed on the defects with high trapping energy which are created on the Al(2)O(3) surface by H(at) pretreatment, yielding highly dense SWCNTs. The pretreatment mechanism of H(at), compared to H(2), is also discussed. It was also found that the quality of SWCNTs can be enhanced when H(at) is flowed with CH(4) during nanotubes growth at low temperature. In this case, the undesired carbon products and defects on catalyst seeds and nanotube walls can be selectively removed by H(at). Therefore it is essential to use H(at) in the pretreatment stage for increasing catalytic activity and to keep the size of nanoparticles in the nm range. H(at) can also be employed in growth stage for enhancing SWCNTs quality and density at low temperature.