Transition from smoothing to roughening of ion-eroded GaSb surfaces

During ion sputtering of GaSb(100) surfaces a transient behavior from initial smoothing to roughening accompanied by self-organized pattern formation has been observed using in-situ x-ray reflectivity and grazing incidence small angle scattering. A characteristic hexagonal dot pattern with a spatial periodicity of 30 nm is observed and the correlation length increases with ion fluence. In the framework of the Bradley-Harper model, where the dot pattern formation results from an interplay of surface roughening due to sputtering and surface smoothing due to diffusion, the initial smoothing behavior results from the same diffusion processes as the pattern formation.