We show how an oxidative pretreatment of Fe, Co, or Ni growth catalyst on SiO support can be used to switch the growth mode of carbon nanotubes from tip growth to root growth, thus favoring the growth of dense, vertically aligned nanotube forests. The oxidative treatment creates a strong catalyst-support interaction at the catalyst-silica interface, which limits the surface diffusion and sintering of the catalyst nanoparticles and binds the catalyst to the SiO surface. This shows that the alignment and growth mode of nanotubes can be controlled, increasing the range of support materials giving dense nanotube forests.
Esconjauregui, S., Fouquet, M., Bayer, B. C., Eslava, S., Khachadorian, S., Hofmann, S., & Robertson, J. (2011). Manipulation of the catalyst-support interactions for inducing nanotube forest growth. Journal of Applied Physics, 109(4). https://doi.org/10.1063/1.3549813