First-Principles Calculations of Adatom-Vacancy Pairs on the Graphene

By using first-principles calculation, we study adatom–vacancy pairs on graphenes. We found that the healing barrier of the adatom–vacancy pair is very small (0.06 eV) when the adatom is bonded to a nearest carbon atom of the mono-vacancy. Therefore, this pair is easily healed. On the contrary, when the adatom is located 4.26–5.54 Å far from the vacant site, the healing barrier becomes high (0.24–0.32 eV), but these barriers are lower than that of the adatom diffusion. It is therefore expected that these adatom–vacancy pairs are healed in low temperature range where the adatom does not diffuse.