Ion bombardment of C60 films

The interaction of energetic ions with C-60 films in the energy range 300-1000 eV is studied by computer simulation. It is found that the firms can be subjected to much more surface damage than would be expected in other forms of carbon. Ejection of particles from the surface takes place in two ways. First, individual carbon atoms can be displaced from the lattice by ballistic collision processes. These are relatively few in number and the phenomenon occurs over a short timescale, of less than 0.5 ps. As the collision cascade develops, energy deposited in the surface region can be transferred to surface C-60 molecules in sufficient quantity for some of these to be desorbed. This phenomena occurs over the order of a few picoseconds and can result in the loss of up to five C-60's from the surface. The damage induced to the lattice causes C-60's to be linked together in the form of polymerised chains. There is also evidence of the formation of 2- and 4-fold co-ordinated bonds in the lattice and transition to amorphous carbon.