Electronic Response of Graphene to Ion Irradiation

Graphene and other two-dimensional materials have recently emerged as promising candidates for novel electronic devices. However, these applications often require high-resolution imaging and processing techniques, which typically employ focused ion beams. Thus, achieving finer control of the structure and properties of graphene necessitates a detailed understanding of the excited electron dynamics occurring in the material in response to ion irradiation. Using real-time time-dependent density functional theory and Ehrenfest dynamics, we simulate 10-80 keV protons traversing monolayer and trilayer graphene. We calculate the secondary electron yield, charge transfer, energy transfer, and equilibration time-scales after impact, and we investigate the dependence of these quantities on graphene thickness, projectile velocity, and projectile trajectory. We find that energy transfer is maximized with a proton energy near 80 keV, while electron emission and charge transfer are maximized with a proton energy near 25 keV.