Nanopatterning of Si surfaces by normal incident ion erosion: influence of metal incorporation on surface morphology evolution

TL;DR

This study investigates how metal incorporation influences the formation of nanodot patterns on silicon surfaces under ion bombardment, revealing a threshold metal concentration for pattern formation and identifying key surface relaxation mechanisms.

Contribution

It demonstrates the critical role of metal concentration in nanodot pattern formation during ion erosion and elucidates the underlying surface relaxation processes involved.

Findings

Nanodot patterns form only above a specific Fe concentration threshold.

Surface relaxation is dominated by ballistic smoothing and ion-enhanced viscous flow.

Transition in spectral density behavior indicates different dominant relaxation mechanisms.

Abstract

The morphology evolution of Si (100) surfaces under 1200 eV Ar+ ion bombardment at normal incidence with and without metal incorporation is presented. The formation of nanodot patterns is observed only when the stationary Fe concentration in the surface is above 8x10^14 cm^-2. This is interpreted in terms of an additional surface instability due to non-uniform sputtering in connection with metal enrichment at the nanodots. At low metal concentration smoothing dominates and pattern formation is thus inhibited. The transition from a k^-2 to a k^-4 behavior in the asymptotic power spectral density function supports the conclusion that ballistic smoothing and ion-enhanced viscous flow are the two dominant mechanisms of surface relaxation.