Angular distributions of sputtered silicon at grazing gallium ion beam incidence

Angular distributions of silicon atoms sputtered by gallium ions at grazing incidence were investigated experimentally and by simulation. The energies and the ion beam fluence studied are typical for using focused ion beam techniques for silicon micro-structuring. The angular distributions of the sputtered atoms at grazing ion beam incidence loose their cylindrical symmetry around the target surface normal due to the anisotropy of single collisions and of the collision cascades initiated by the energetic ions. The angular distributions were studied in this work both experimentally and using the simulation methods of Monte-Carlo and of Molecular Dynamics. To study the influence of the surface structure on the angular distributions of the sputtered atoms, different arrangements of silicon atoms on the surface of the targets were tested in simulations using Molecular Dynamics. Monte-Carlo simulations based on the theory of binary collisions were used to complement the experimental results on the angular distributions of sputtered silicon and the final results are presented as an analytical model.