Characterization of spin-capable multi-walled carbon nanotubes grown an a Fe catalyst film under helium gas

Abstract

Spin-capable multi-walled carbon nanotubes (MWCNTs) were synthesized on a Fe catalyst film in a He environment by using thermal chemical vapor deposition (CVD). The effect of He on the growth behavior of the MWCNTs was investigated. In addition, the variation of the Fe surface during the pre-annealing and MWCNT growth processes was characterized using scanning electron microscopy, X-ray diffraction and atomic force microscopy. It was surmised that the presence of He gas did not help in the formation of Fe nanoparticles on the substrate during the pre-annealing or the growth processes; however, He gas did appear to help activate and/or assist carbon to diffuse into the surface of the Fe nanoparticles. We note that MWCNT forests grew well on the Fe catalyst film even without the pre-annealing process. The characteristic dimension of the MWCNTs was found to be the same as the particle size and the crystallite size of the nanoparticles formed on the substrate. We also found that spin-capable MWCNTs could be grown by controlling the density of nanotubes on the substrate.