First principles study of native defects in a graphitic BC2N monolayer

Spin polarized density functional theory has been used to investigate the stability and electronic properties of antisites and vacancies in graphitic BC2N sheets. Likewise as we observed in nanotubes, we found that, in a boron-rich system, a boron atom occupying a carbon site (BCII) and a carbon atom occupying a nitrogen site (CN), should present the lower formation energy. However, in a nitrogen-rich system, a nitrogen atom occupying a carbon site (NCI) and carbon atom occupying boron site (CB), should present the lowest formation energies. These antisites lead the BC2N monolayer to exhibit acceptor and donor properties. We also observed that antisites that introduce homogeneous B–B and N–N bonds (BCI, NCII, BN and NB) give rise to deep electronic levels in the band gap. According to our calculations, vacancies should present higher formation energies than the antisites and we also noticed that for vacancies the reconstruction around the defective site depends on the missing atom and does not follow the same trend as observed for nanotubes. The electronic properties are ruled by the under-coordinated atoms that typically lead the system to present a localized magnetic moment.