Published online by Cambridge University Press: 17 March 2011
Bombardment of slightly rough, planar surfaces with an energetic gas-cluster ion beam (GCIB) is known to result in a decrease in roughness. We report comparison of measured surface evolution with simulations based on a simple phenomenological model. The model consists of a continuum rate equation for the surface height undergoing multiple cluster impacts. With suitable assumptions the main features observed in the evolution of an initially nonplanar surface can be simulated. Qualitatively, both experiment and simulation show that sharp features and asperities are rapidly eroded. Examples are given of initial surfaces that are either randomly rough and scratched, or very smooth with added nanoscale engineered features. Both types of surfaces show smoothing in microscopy evaluations of the GCIB and in the simulations, thereby identifying impact-transient surface diffusion as the primary cluster smoothing mechanism.