Orientation dependent sputter yield of aluminium

During nitrogen plasma immersion ion implantation (PIII) of aluminium, a strong variation of the surface structure across the surface was observed. Some of the grains exhibit a nearly flat surface, while others show a strongly corrugated relief with a high roughness. A similar effect was seen for sputtering a polycrystalline aluminium sample with 5 keV Cs ions at an incident angle of 60°. A variation of the sputter yield of up to 20% is observed, together with different surface morphologies for differently oriented grains, as determined by analysis of electron backscatter patterns (EBSP). We conclude that a small difference in the surface binding energy for different surface planes may lead to the observed variation of surface topography by a sputter yield depending on the particular grain orientation. Variations of diffusion constants and surface adsorbates with crystallographic direction may further contribute to the observed heterogeneity.