Density-Functional Based MD Studies of Low-Energy Atom Collisions onto Diamond and Graphite

The near-surface implantation of hyperthermal neutral atoms with (15 - 75) eV onto diamond (111) and graphite substrates is studied by molecular-dynamics (MD) using a density-functional (DF) based non-orthogonal tight-binding (TB) scheme. Depending on the initial energy and the impact point the atoms penetrate beneath the surface forming regions of local disorder and stress. The energy partition during the collision is analyzed yielding results about penetration and displacement threshold. After a final relaxation of the structures the penetration depths of the colliding particles are determined. The structural topology and the electronic properties of the induced defects and surface modifications are discussed. The penetration thresholds for noble gas atoms, hydrogen and carbon and the atomic-size dependent bulge arising after the subplantation process into a graphite substrate have been determined.