Cooperative mixing induced surface roughening in bilayer metals: a possible novel surface damage mechanism

TL;DR

This study uses molecular dynamics simulations to reveal a novel surface damage mechanism in bilayer metals, where cooperative atomic transport during ion irradiation causes surface roughening and cavity growth.

Contribution

It uncovers a new surface damage mechanism driven by cooperative mixing and atomic transport in bilayer metals under ion irradiation.

Findings

Surface roughening is enhanced by interfacial mixing.

Atomic mass difference influences the process.

Surface cavity growth occurs under high-dose irradiation.

Abstract

Molecular dynamics simulations have been used to study a collective atomic transport phenomenon by repeated Ar$^+$ irradiations in the Ti/Pt interfacial system. The ion-induced injection of surface atoms to the bulk, the ejection of bulk atoms to the top layers together with surface erosion is strongly enhanced by interfacial mixing. This process leads to a dense interfacial material, and broadening of the interface region. The process scales with the relative difference of the atomic masses. We find that surface roughening and interfacial mixing is strongly coupled via an enhanced counterflow material transport normal to the surface which might be a novel surface damage mechanism. This cooperative phenomenon is active when the bilayer system is subjected to a high dose ion irradiation (multiple ion irradiations) and leads to surface cavity growth.