First-principles study on migration and coalescence of point defects in monolayer graphene

Graphene is a promising material due to its outstanding properties. Point defects can be created artificially and tailor/improve the relative properties of pristine graphene. Defective graphene is potential material for electronic devices and sensors. Under irradiation or heat treatment, defects may diffuse and aggregate together. Here we perform density functional theory (DFT) to illustrate the migration and coalescence processes of the point defects. We find that the presence of single-vacancy (SV) defect stimulates the migration of another SV defect to bring them together and form the adjacent single vacancy defects. The adjacent single vacancy defects can combine into a divacancy defect, and we study the path. We also study the structural rearrangement of divacancy defect and conclude the relative stability of different types of divacancy defects. In addition, we find that divacancy defect [V₂ (5-8-5) defect] is ready to be healed by a neighboring adatom defect. In comparison, divacancy defect [V₂ (555-777) defect] cannot be healed by an adatom defect directly. Our results provide the mechanism of migration and coalescence processes of point defects in graphene, which is useful for nanoengineering of graphene with defect. © 2013 American Chemical Society.