Energy dependence of quantum dot formation by ion sputtering

Ordered quantum dot patterns are generated on GaSb and InSb surfaces due to a surface instability induced by Ar⁺-ion sputtering at normal incidence. The characteristic length of the generated patterns scales with the square root of the ion energy over the energy range of 75--1800 eV. This energy dependence is compared to the solutions of the isotropic Kuramoto-Sivashinsky equation and allows the determination of the lateral width of the energy distribution deposited by the incident ions in the very-low-energy range. We show that the observed energy dependence is in agreement with the linear continuum theory under the assumption that the dominant smoothing process is due to effective ion-induced diffusion without mass transport on the surface.