Order enhancement and coarsening of self-organized silicon nanodot patterns induced by ion-beam sputtering

The temporal evolution of the characteristic wavelength $(λ)$ and ordering range $(ξ)$ of self-organized nanodot patterns induced during $Ar+$ ion beam sputtering on Si(001) and Si(111) surfaces is studied by atomic force microscopy and grazing incidence x-ray diffraction. The patterns exhibit initial coarsening of $λ$ (up to $54–60nm$⁠) and increase in $ξ$ (up to $400–500nm$⁠) after which both features stabilize. The pattern formation is only weakly controlled by the crystallographic surface orientation, Si(111) surfaces showing a faster evolution into a proper stationary state. This trend is attributed to a higher sputtering rate at this orientation, as confirmed by theoretical simulations.