Modelling surface restructuring by slow highly charged ions

TL;DR

This paper presents a theoretical study of how slow highly charged ions impact alkaline earth halide surfaces, leading to surface modifications like etch pits and nano-hillocks, supported by molecular dynamics simulations.

Contribution

It introduces a model explaining surface restructuring mechanisms due to ion impact and identifies energy thresholds for different surface modifications.

Findings

Identification of two energy thresholds for surface modifications

Qualitative agreement between simulations and experimental observations

Proposal of mechanisms converting ion energies into surface changes

Abstract

We theoretically investigate surface modifications on alkaline earth halides due to highly charged ion impact, focusing on recent experimental evidence for both etch pit and nano-hillock formation on CaF2 [A. El-Said et al, PRL 109, 117602 (2012)]. We discuss mechanisms for converting the projectile potential and kinetic energies into thermal energy capable of changing the surface structure. A proof-of-principle classical molecular dynamics simulation suggests the existence of two thresholds which we associate with etch pit and nano-hillock formation in qualitative agreement with experiment.