Scaling behavior of the penetration depth of energetic silver clusters in graphite

Molecular dynamics simulations have been carried out to determine the penetration depth for implantation of Ag clusters incident normally on graphite in the energy range 0.5-5 keV. The mean penetration depth for Ag-7 clusters is found to be linearly dependent on the impact velocity but there is a transition to a more linear scaling of depth with energy as the cluster size increases. An explanation for this behavior is given in terms of the different natures of the collision cascades over picosecond time scales. The results are in good agreement with corresponding experimental measurements of the penetration depth.