HYPERTHERMAL COLLISIONS OF SILICON CLUSTERS WITH SOLID-SURFACES

High yields of intact scattering are found for collisions of mass-selected Si(N)+/- clusters (N = 5-24) against graphite and silicon surfaces, at impact energies of 0.5-10 eV/atom. This result indicates an unanticipated difficulty in forming bonds during the impact event. The reflected cluster fragments or emits an electron in patterns consistent with gas-phase energetics, and analysis of fragmentation rates specifies an internal energy content of 12-26 percent of the impact energy, depending on cluster size, the surface, and surface temperature. Reactive processes, such as sticking or adhesion, may still dominate at lowest and highest energies.