Band Gap Opening in Dual-Doped Monolayer Graphene

By means of periodic density functional calculations, we have studied the effect of dual doping on the stability and electronic structure of graphene. To this end, we substituted two carbon atoms with one 2p element (B, N, or O) and one 3p element (Al, Si, P or S). We determined that, in all cases, dual doping is much easier to attain than the introduction of only one dopant into the graphene framework. We demonstrate that this conclusion does not depend on the chemical species used to compute the formation energies. Moreover, we show what condition the dopants must satisfy to prefer dual doping over monodoping. Regarding the electronic properties, we found that, in most cases, the gaps computed at the HSE level for the dual-doped graphenes are smaller than those estimated for monodoped graphenes, despite the lower concentration of dopant present in the latter. In effect, for some dual-doped graphenes, the structures of the Dirac cones were found to be preserved, and gaps as small as 0.02 eV were computed.