Atomic Beam Interactions with Silicon (111) Surfaces: A Molecular Dynamics Study

Low energy (5–20 eV) atomic beam-surface interactions have been studied using a molecular dynamics technique. Silicon atoms are directed at an unreconstructed (111) silicon substrate either perpendicular to the surface or at grazing angles of incidence from 10–35°. The Si-Si interaction is treated using an empirical many-body silicon potential so that the effects of covalent bonding are included. At general beam orientations relative to the surface, low energy atoms are rapidly adsorbed at the surface, whereas at higher energies they either bounce off the surface or penetrate into the substrate. However, when the surface component of beam momentum is parallel to a (100) symmetry direction, Si atoms, under certain conditions, are found to channel along the surface rows, resulting in very little local excitation of the surface geometry and only gradual energy loss. The vertical momentum is carried away by substrate lattice vibrations, and the particle is guided along the surface by interaction with the atoms making up the surface ‘half-channels’. This surface channeling effect offers considerable promise for delicate control of the beam-induced annealing/growth of non-equilibrium surface geometries, and thus for high-quality growth at low temperatures.