B and N doping in graphene ruled by grain boundary defects

The energetics and electronic properties of substitutional B (B-C) and N (N-C) doping, and BN codoping in graphene with distinct grain boundary defects were investigated by ab initio simulations. Our results indicate that a single B or N impurity atoms and an isolated BN pair prefer to incorporate into the grain boundary region. In particular, we find that the formation of N-C along the grain boundary sites is an exothermic process. It suggests that hexagonal-BN (h-BN) or h-BN and carbon (h-BNC) domains may be patterned by these defective regions. The electronic properties of those doped grain boundary systems have been examined through scanning tunneling microscopy (STM) simulations and electronic band-structure calculations. We find a quite different STM picture for the B-C- and N-C-doped grain boundaries when compared with the same impurities on the perfect graphene sheet.