Dependence of SWNT Growth Mechanism on Temperature and Catalyst Particle   Size: Bulk versus Surface Diffusion
  MD simulations reveal that many aspects of SWNT nucleation and growth from solid and liquid metal particles are similar. In both cases graphitic islands lift off the cluster surface to form caps that grow into SWNTs. However, in contrast to liquid particles, where C atoms primarily diffuse into the bulk of the cluster before adding to the growing SWNT, incorporation of C into SWNTs on solid particles occurs predominantly via surface diffusion. 
Feng Ding, Arne Rosen, Kim Bolton