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, SiO 2 ) monolayers of MoS 2 with highly charged xenon ions (HCIs; charge state: 17+ to 40+), extracted the emitted neutral postionized Mo particles in a timeof-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 pot and E kin .

Charge exchange of slow highly charged ions from an electron beam ion trap with surfaces and 2D materials

“…For the latter two, there exist many literature data for studies including bulk samples, however, only scarce information is available for HCI interaction with (freestanding) 2D materials. There is solely a study by Skopinski et al using MoS 2 layers on Au (111) substrate revealing that sputtered Mo atoms by highly charged xenon ions have energies on the order of only 1 eV [102].…”

“…To conclude this second phase of ion-solid interaction: The deexcitation of the hollow atom formed in step 1 (charge exchange discussed in section 3.1) and the accompanying potential energy deposition may trigger the emission of secondary particles through either sputtering [102], radiative decay [103] or non-radiative decay [68,107].…”

Manipulation of the electrical and memory properties of MoS2 field-effect transistors by highly charged ion irradiation

“…Recent time-of-flight mass spectrometry experiments show that the kinetic energy of the HCIs has to be taken into account to account for ion-induced damage of substrate supported MoS 2 and that the type of the substrate is important. 40 With the parameters used in this work we thus expect pores in the MoS 2 and a substantial amount of defects in the underlying substrate.…”