Implantation of size-selected Si clusters into graphite

Molecular dynamics simulations have been performed to explore the implantat ion of silicon clusters into a graphite substrate to well-defined depths. T he cluster sizes range from N=20 up to N=200 atoms per cluster, deposited w ith kinetic energies from E=500 eV up to E=5000 eV per cluster. We find tha t the clusters remain intact as coherent, amorphous structures after implan tation. The implantation depth is well defined and scales with the kinetic energy of the clusters and the inverse of the cross-sectional area. This in dicates a constant decelerating force, associated with the lateral displace ment of carbon atoms as the cluster "drills a hole" in the substrate. The m ain dissipation channels for the energetic silicon clusters are the creatio n of phonons in the graphite substrate and the breaking of C-C bonds. (C) 2 000 American Institute of Physics. [S0003-6951(00)04345-X].