Periodic Trends of Pnictogen Substitution into a Graphene Monovacancy: A First-Principles Investigation

We present a theoretical investigation on the electronic properties and formation energetics of pnictogen substitution into a graphene monovacancy. Our work elucidates the fundamental interactions that occur between the dopant and graphene, which ultimately dictate the observed behavior of the material. We find a linear trend for the energy of formation proceeding down group 15 of the periodic table. Further, we observe the formation of a protrusion at the monovacancy site, which is particularly conspicuous for larger pnictogens. This blistering can be attributed to charge transfer between the substituted heteroatom and the bordering carbon atoms of the monovacancy. Reorganization of the defect site of graphene becomes more pronounced for the latter pnictogens antimony and bismuth. An interaction regime emerges among this group, whereby nitrogen and phosphorus chemisorb strongly to the vacancy site, arsenic weakly chemisorbs, while antimony and bismuth physisorb to the surface. These interactions introduce moderate band gaps and yield impurity states near the Fermi energy, similar to a doped semiconductor material. Moreover, the extent of chemical bonding and planarity notably alters the band structure and the accessibility of low lying energy states, which are important for charge transport and reactivity. This work suggests the possibility of tailoring graphene surfaces for electronic devices or chemical transformations of interest via the appropriate choice of pnictogen dopant.