Velocity distributions of particles sputtered from supported two-dimensional MoS2 during highly charged ion irradiation

Abstract

A key problem in ion-solid interaction is the lack of experimental access to the dynamics of the processes. While it is clear that the mechanisms of interaction and sputtering depend on the kinetic and potential energy (sum of ionization energies) of the projectile, the importance and interplay of the various interaction mechanisms are unknown. Here, we have irradiated substrate-supported (Au, ${\mathrm{SiO}}_{2}$) monolayers of ${\mathrm{MoS}}_{\text{2}}$ with highly charged xenon ions (HCIs; charge state: $17+$ to $40+$), extracted the emitted neutral postionized Mo particles in a time-of-flight mass spectrometer, and determined their velocity distributions. We find two main contributions, one at high velocities and a second at lower velocities, and assign them to kinetic and potential effects, respectively. We show that for slow HCIs (5 keV) the interaction mechanisms leading to particle emission by electronic excitation and momentum transfer, respectively, are independent of each other, which is consistent with our atomistic simulations. Our data suggest that the predominant mechanism for potential sputtering is related to electron-phonon coupling, while nonthermal processes do not play a significant role. We anticipate that our work will be a starting point for further experiments and simulations to better understand the interplay of processes arising from ${E}_{\text{pot}}$ and ${E}_{\text{kin}}$.