A simple model of the initial stages of sputtering is developed. Terrace-ar
ea distribution, i.e., the distribution of exposed area fractions, and surf
ace roughness during low-energy ion bombardment of an initially flat single
-crystal surface can be computed. The results compare well with previously
published experimental work [Poelsema et al., Phys. Rev. B 41, 11 609 (1990
)] and allow for the determination of the sum of sputtering and adatom yiel
ds from thermal energy helium atom scattering data.