Evolution of gold thin films to nanoparticles using plasma ion bombardment and their use as a catalyst for carbon nanotube growth

We investigate the evolution of Au thin films to nanoparticles caused by plasma ion bombardment and report their validity as a catalyst on the growth of carbon nanotubes (CNTs). The Au thin films having 1-50 Å thickness ranges were precisely prepared by electron beam deposition. The plasma ion bombardments with the plasma power from 5 to 15 W were performed at 500 C for 10 min under 1.33 × 10² Pa of Ar to investigate the effects of plasma power on the surface structures. It is interesting that the mean size of Au nanoparticles increased as plasma power gets high in the thinner film cases, which might be the results of sputtering and surface diffusion-related aggregation. On the contrary, the mean particle size of the thicker films decreased at lower plasma power regime due to the sputtering, then, increased again at the highest plasma power, which might be caused by the diffusion-induced aggregation of the films. Finally, to investigate the catalytic ability of the thin film-induced Au nanoparticles, we grew CNTs by a thermal chemical vapor deposition with a methane source. It was found that the Au nanoparticles obtained from the plasma-treated 5 Å thick films act as an efficient catalyst for the growth of single-walled CNTs.