Trajectory studies of hyperthermal Xe scattering from GaAs(110)

We present the results of stochastic classical trajectory simulations of the scattering of a nonreactive gas, xenon, from a semiconductor surface of known structure and electronic and vibrational properties, GaAs(110). The range of incident energies considered is 1 to 8 eV, in order to make direct comparison with results of molecular beam experiments reported in the accompanying paper. We employed a 48-atom three-layer slab of GaAs, with periodic boundary conditions in two dimensions and frictional and stochastic forces in the third (surface normal) dimension. Pairwise additive Lennard-Jones potentials describe the gas-surface interaction. The calculations reproduce the large energy exchange and surprising structural sensitivity observed experimentally. Energy transfer is dominated by an initial binary interaction of the Xe with a single Ga or As atom. The repetitive collision nature of this binary encounter produces angular scattering patterns very similar to those obtained for scattering of light atoms, including "rainbow maxima." The mechanism of energy deposition may have implications to "gentle" sputtering by neutral atom bombardment and to collision induced excitation of electron-hole pairs.