Modification of graphene supported on SiO₂ substrate with swift heavy ions from atomistic simulation point

The damage production induced by swift heavy ion (SHI) irradiations in graphene supported on a SiO₂ substrate is investigated using molecular dynamics method. The thermal spike model is used to simulate the energy deposited into the lattice due to electron-phonon coupling. By given energy to both the graphene and substrate, we find that carbon chain structures even nanoholes can be produced, which depends on the deposited energy. The minimum value needed to generate defects in supported graphene is higher than 6.5 keV/nm, which is higher than the threshold value for track formation in SiO₂. For a suspended graphene sheet, the value is determined to be 8 keV/nm. Thus our results indicate that the presence of SiO₂ substrate decreases the damage threshold of graphene. Our simulation further suggests that the damage of supported graphene is due to the synergic effects from direct collision and indirect impact from the substrate. The defect production in supported graphene is along with the formation of ion tracks in SiO₂ substrate and the rupture of graphene is initiated from the track core region. Our results provide an atomistic explanation for the reported modification of graphene with SHIs, which is very important for engineering graphene with SHIs.