Void Swelling Induced Surface Modifications: Exploring the Relation between the Crystallographic Orientation and Surface Facets

The phenomenon of surface facet formation during ion implantation has captured considerable scientific and technological interest. Surface facets-including wavy, pyramidal, and terraced morphologies-are typically formed during off-normal keV and MeV ion beam implantation, and due to injected gas effects. In certain circumstances, these features may also emerge during irradiation at normal incidence: when differential sputtering occurs in biphasic regions, when contaminants are inadvertently added as dopants, or when the experimental arrangement permits the coimplantation of metals. The formation of surface nanopatterns in nanocrystalline nickel under high-temperature ion irradiation at normal incidence has been observed-a phenomenon that conventional mechanisms fail to explain. A novel mechanism driving nanopattern formation under these conditions is presented. These findings offer compelling evidence that facets result from voids forming on the surface and in its vicinity. A strong correlation between the crystallographic orientation and the facet type has also been identified. Specifically, grains oriented in the and directions display smooth and wavy morphologies, while grains with orientations in between exhibit more complex shapes. The research indicates that grains with low stress and surface energies tend to exhibit wavy facets, while higher values lead to the formation of more complex shapes.