Effect of Si-C bond formation in 20 keV C₆₀ bombardment of Si

We have performed molecular dynamics (MD) simulations to investigate the effect of Si-C bond formation on fluence-dependent results in 20 keV C ₆₀ bombardment of Si. Sputter depth profiling experiments of C ₆₀ on Si have produced atypical results, which are thought to be caused by the strong covalent bonds that are formed between the C atoms in the projectile and Si atoms in the substrate. A recently developed scheme developed by Russo, et al.8 has been adapted to perform MD simulations of 150 successive impacts of 20 keV C₆₀ on Si, which corresponds to a total fluence of 2.64 × 10¹³ impacts/cm². In order to isolate the effects of Si-C bond formation, the same set of trajectories is calculated with and without the attractive Si-C potential energy terms. When Si-C bonds are able to form, nearly all the C atoms from the projectile are incorporated into the substrate. When the possibility of Si-C bond formation is removed, most of the C atoms are backscattered into the vacuum. The cumulative result is that the substrate with Si-C bonds contains a factor of twenty times more C atoms, which are located below the surface.