Hyperthermal gas-surface scattering.

We summarize our recent results of scattering hyperthermal (1-15 eV) rare gas atoms from single crystal semiconductors. These include collisional excitation of carriers in the semiconductor, the ejection of charged and neutral surface particles, and the projectile scattering distributions characteristic of the strongly inelastic collisions. The dependence of the electronic excitation of the semiconductor upon the incident energy, angle, and atom are consistent with the creation of a local thermal hot spot with which there is fast electronic equilibration. In contrast, for the ejection of ions from the surface, the incident and ejected particle energy and angle distributions suggest direct, large momentum transfer processes. The scattered rare gas atom distributions exhibit large energy loss, yet are strongly structured and surprisingly sensitive to surface topography. A simple collision mechanism is discussed which describes much of the qualitative phenomena observed.