Identifying atomic sites in N-doped pristine and defective graphene from ab initio core level binding energies

Theoretical calculations have been carried out to predict N(1s) binding energy values in N-doped graphene which take into account initial and final state effects. A simple way to carry out ΔSCF Hartree-Fock calculations is proposed, validated against experiment for a series of N-containing organic molecules and applied to realistic N-doped nanosized pristine and defective graphene models. Final state effects appear to be important and strongly suggest that only two types of N are likely to be detected on N-doped pristine graphene by X-ray Photoelectron Spectroscopy with binding energy values of 398.6 and 400.5 eV, respectively and relative to C(1s) at 285 eV in agreement to recent experiments for quasi free standing N-doped graphene. Two cases of N-doping in defective graphene have also been considered and calculated results compared with recent experimental measurements. Calculated values for C(1s) including final state effects strongly suggests that values for core level binding energy of N and other dopants will be close to their absolute values if referred to C(1s) at 290.2 eV. The proposed approach is general enough to be successfully applied to other cases of interest.