The well-controlled growth of carbon nanotubes (CNTs) at low temperature (< 1073 K) using non-iron group metal catalysts remains a challenge. Here, we report that CNTs can be grown at 773–1173 K over an atomic layer epitaxy (ALE) prepared copper catalyst (ALE-Cu/SiO₂) using chemical vapour deposition in helium diluted ethylene. At the same reaction conditions, only amorphous carbon can be generated over an impregnation (IM) method prepared copper catalyst (IM-Cu/SiO₂). A metal-support interaction (MSI) model is proposed to describe the interaction between the ALE prepared Cu nanoparticles (NPs) and SiO₂ support through the results of temperature programmed reduction profiles, X-ray photoelectron spectra and in situ X-ray diffraction (XRD) patterns. Structurally stabilised CuNPs in ALE-Cu/SiO₂ catalyst indicate that the strong MSI site of CuNPs and/or copper silicide (Cu₃Si) evidenced by in situ XRD patterns would be the active centers to fabricate CNTs. Our observations provide new insights into controlling the CNT growth at low-temperatures over non-ferromagnetic catalysts.

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.