Silicon-carbon bond inversions driven by 60 keV electrons in graphene

We demonstrate that 60 keV electron irradiation drives the diffusion of threefold coordinated Si dopants in graphene by one lattice site at a time. First principles simulations reveal that each step is caused by an electron impact on a C atom next to the dopant. Although the atomic motion happens below our experimental time resolution, stochastic analysis of 38 such lattice jumps reveals a probability for their occurrence in a good agreement with the simulations. Conversions from three- to fourfold coordinated dopant structures and the subsequent reverse process are significantly less likely than the direct bond inversion. Our results thus provide a model of non-destructive and atomically precise structural modification and detection for two-dimensional materials.