Does the thermal spike affect low-energy ion-induced interfacial mixing?

TL;DR

This study uses molecular dynamics to investigate if thermal spikes influence ion-induced interfacial mixing in Ti/Pt multilayers, finding that mixing mainly occurs after thermal spikes and is not sensitive to heat of mixing.

Contribution

The paper demonstrates that thermal spikes do not significantly affect interfacial mixing in Ti/Pt under 1 keV ion impacts, challenging existing thermal spike models.

Findings

Mixing occurs mainly after thermal spikes during relaxation.

Heat of mixing does not significantly influence mixing.

Unusual mixing behaviors like phase delay and double peaks observed.

Abstract

Molecular dynamics simulations have been used to obtain the three-dimensional distribution of interfacial mixing and cascade defects in Ti/Pt multilayer system due to single 1 keV $Ar^+$ impacts at grazing angle of incidence. The Ti/Pt system was chosen because of its relatively high heat of mixing in the binary alloy and therefore a suitable candidate for testing the effect of heat of mixing on ion-beam mixing. However, the calculated mixing profile is not sensitive to the heat of mixing. Therefore the thermal spike model of mixing is not fully supported under these irradiation conditions. Instead we found that the majority of mixing occurs after the thermal spike during the relaxation process. These conclusions are supported by liquid, vacancy as well as adatom analysis. The interfacial mixing is in various aspects anomalous in this system: the time evolution of mixing is leading to a phase delay for Ti mixing, and Pt exhibits an unexpected double peaked mixing evolution. The reasons to these effects are discussed.