Auger Decay Facilitated Vacancy Formation in PtSe ₂ Monolayer under Electron Beam

Electron-beam-induced uncontrolled damage formation limits the development of two-dimensional (2D) materials; however, the underlying mechanisms of inelastic interactions, particularly the impact of carrier dynamics through various cooling pathways, remain insufficiently understood. Using real-time time-dependent density functional theory (rt-TDDFT) coupled with nonadiabatic molecular dynamics (NAMD), we reveal that inelastic interactions together with carrier cooling induce charge-state transitions significantly lower the threshold of vacancy formation compared with pure elastic knock-on predictions. Specifically, for excitation initiated from the middle level of the valence band, the ionization-plus-excitation state generated after Auger decay is recognized as the primary driver of lowering the onset of structural instability. Using monolayer PtSe₂ as a case study, the calculated beam energy required for Se ejection after ionization followed by Auger decay (∼70 keV) agrees reasonably well with the experimentally observed onset for vacancy creation (∼60 keV), significantly revising the much higher prediction (∼150 keV) from conventional DFT. This study identifies Auger decay as an important factor in electron-beam-induced structural instability, providing a critical theoretical basis for quantitative damage modeling and paving the way for precise atomic manipulation in 2D materials.