Unraveling energy loss processes of low energy heavy ions in 2D materials

Structuring of 2D materials and their heterostructures with ion beams is a challenging task, because typically low ion energies are needed to avoid damage to a substrate. In addition, at the very first monolayers of a material, ions are not yet in charge equilibrium, i.e. they may either charge up or neutralize depending on their velocity. The change in electronic structure of the ion during scattering affects the energy, which can be transferred to the recoil and therefore the energy available for defect formation. In order to make reliable use of ion beams for defect engineering of 2D materials, we present here a new model for charge state and charge exchange dependent kinetic energy transfer. Our model can be applied to all ion species, ion charge states, and energies. It is especially powerful for predicting charge state dependent stopping of slow highly charged ions.