Atomistic Simulations of Defects Production under Ion Irradiation in Epitaxial Graphene on SiC

Using first-principles and analytical potential atomistic simulations, we study the production of defects in epitaxial graphene on SiC upon ion irradiation for ion types and energies accessible in helium ion microscope. We focus on graphene-SiC systems consisting of the buffer (zero) graphene layer and SiC substrate, as well as one (monolayer) and two (bilayer) additional graphene layers. We calculate the probabilities for single, double and more complex vacancies to appear upon impacts of energetic ions in each graphene layer as functions of He and Ne ion energies, and compare the data to those obtained for the free standing graphene. The results indicate that the role of substrate is minimal for He-ion irradiation with energies above 5 keV, which can be associated with a low sputtering yield from this system upon ion irradiation, as compared to common Si/SiO2 substrate. In contrast, SiC substrate has a significant effect on defect production upon Ne-ion irradiation. Our results can serve as a guide to the experiments on ion irradiation of epitaxial graphene to choose the optimum ion beam parameters for defect-mediated engineering of such systems, e.g., for creating nucleation centers to grow other two-dimensional materials, such as h-BN, on top of the irradiated epitaxial graphene.