Transition of nano-ripple to nano-hillock pattern on ion bombarded Si with an enhanced hydrophobicity

Abstract

Surface patterning in nano-scale dimension and the effect of surface heterogeneity to control surface properties like wettability of solid surfaces have been studied here. This work focuses primarily on the generation of Si nano-patterns at oblique incidence via ion beam assisted impurity co-deposition technique and its impact on the wetting property of liquid. When oblique ion irradiation is performed on a Si surface without impurity, ripple structures evolve that show an increase in its hydrophilic behavior with a rise in ion fluence. On the other hand, the inclusion of stainless steel as seeding material during bombardment brings about a noteworthy change in the surface topography with the emergence of hillocks structures over the ripple morphology. For a higher bombardment time, the Si rippled surface is seen to vanish and a transition from nano-ripple to nano-hillock pattern is witnessed. Such an unusual pattern evolution is aided by FeSi2 bond which further promotes an increase in surface hydrophobicity. Contact angle measurements show directional dependence behavior having a direct influence of the anisotropic patterns synthesized here.