Self-assembly formation of multi-walled carbon nanotubes on gold surfaces.

We report on the observation of self-assembled carbon nanostructures on a standard transmission electron microscopy (TEM) Au substrate formed via thermal chemical vapor deposition. Multi-walled carbon nanotubes (MWNTs) and other carbon nanostructures (CNs), such as carbon nanofibers and carbon nanoparticles (NPs), could be fabricated through structural transformation of metastable carbon layers on the Au surface during 800-850 °C with the thermal decomposition of ethylene. At these temperatures, we found that Au NPs will form immediately through the structural transformation of the Au grid surface in helium atmosphere. The Au NPs work as active centers to trigger the decomposition of ethylene into carbon atoms, which form metastable carbon layers or amorphous carbon nanobugs, and then form CNs via self-assembling. The growth of CNs was characterized by field-emission scanning electron microscopy (SEM), high-resolution TEM and RAMAN spectroscopy. The transformation of amorphous carbon nanobugs by electron beam irradiation is also recorded by in situ monitoring of TEM.