Investigation on the electronic structure of BN nanosheets synthesized via carbon-substitution reaction: the arrangement of B, N, C and O atoms

Graphene-like BN nanosheets were synthesized via carbon-substitution reaction using graphene as a template in an attempt to produce C-doped BN. The carbon residue was removed by high-temperature oxidation in air. The role of the graphene template and oxygen with regard to the local structure of BN and its defect-related optical luminescence are investigated using X-ray absorption near-edge structure (XANES) and X-ray excited optical luminescence (XEOL). The structure and bonding of B, N, C and O in different chemical environments before and after oxidation are revealed by XANES. It is found that B and N atoms tend to form large BN domains, whereas the formation of B-C or N-C bonding is not significant. Two types of O local structures are found under different oxidation temperatures, as revealed by XANES: moderate oxidation results in O substituting N, while B2O3-like local structure is formed under higher oxidation temperature. The two types of O-related defects exhibit different luminescence properties.