Effect of simultaneous Ne+ ion bombardments on bonding structure of carbon films deposited from thermally evaporated C60 fullerene

Carbon thin films have been deposited on Si(111) wafers through thermally evaporated C 60 with simultaneous bombardments of Ne + ions. C 60 film can be prepared for Ne + ion energy up to 500 eV, indicating the high stability of the cagelike structure of the C 60 molecule. The conversion from C 60 structure into amorphous carbon takes place on increasing Ne + ion energies to 700 eV, in which a morphological change from a nodule-like surface to featureless structure is observed. With further increase of Ne + ion energies from 1 to 5 keV, the surface roughness of the amorphous carbon films is enhanced, while a higher fraction of sp 3 bonding and a larger optical bandgap are obtained at relatively low Ne + ion energies. These suggest that the ion sputtering is not only responsible for the surface roughening but also has significant influence on the bonding structure in ion-assisted amorphous carbon films.