Nucleation of carbon onions and nanocapsules under ion implantation at high temperature

In-situ and ex-situ TEM observation was performed in copper implanted with carbon ions at temperatures from 570 to 973 K. Carbon onions (concentric graphitic spheres) and nanocapsules (concentric graphitic spheres with cavities) were observed together with amorphous carbon layers. Statistics of cluster size as a function of ion fluence, implantation temperature and substrate crystallinity gave insights into the nucleation processes of onions and nanocapsules. One is the formation of graphitic layers on grain boundaries to encapsulate copper particles. The other is the nucleation of graphitic cages, probably fullerenes, due to both high concentration of carbon atoms and high amount of radiation damage. Simultaneous observation of microstructural evolution under implantation revealed that onions were formed inside the substrate, not surface and that they segregate at the surface due to radiation-enhanced evaporation. (C) 2001 Elsevier Science B.V. All rights reserved.