Presence of reactive impurities in Ar+ ion beam plays a key role for Si ripple formation

Abstract

We report the decisive role of reactive ion impurities in the low energy Ar+ ion beam on surface nanopattern formation. The effects of co-deposited impurities on pattern formation during ion bombardment have already been reported, but the effect of beam impurities is something new which has not been considered earlier. The possible source of experimental variance in the low energy (few keV to 10’s of KeV) Ar+ ion beam induced nano ripple formation has been identified by irradiating Si surface at an oblique angle incidence with the pure and impure Ar+ ion beam of energy 3–10 keV. No well-defined patterns are observed for the mass selected pure Ar+ ion bombardment, whereas well defined periodic ripple pattern is formed by the same experimental condition with the impure mass unanalyzed Ar+ ion irradiation. The contaminants in the mass unanalyzed beam specifically reactive nitrogen, oxygen, and carbon play the main role of pattern formation by introducing chemical instability on the Si surface. The surface morphologies of the irradiated Si surfaces are examined by Atomic Force Microscopy (AFM), whereas the surface contamination and corresponding chemical compound formation are investigated by X-ray photoelectron spectroscopy (XPS).