Hole doping by adsorption of oxygen on a Stone–Thrower–Wales defect in graphene

Adsorption of an O2 molecule on a graphene sheet with and without a Stone–Thrower–Wales (STW) defect is examined by the density-functional theory calculations. The presence of an O2 molecule or a defect breaks the usual symmetry of graphene, and thus the electronic structure is examined in detail by the three-dimensional plot of the energy surfaces of the spin-dependent two-dimensional band structure. The energetics have clarified that O2 physisorption is possible for graphene with and without STW defects. The O2 physisorption does not trigger opening of the band gap around K point, while it induces holes in the majority-spin π band of graphene. The number of holes induced by one O2 molecule is calculated from the density of states (DOS) as 0.0087 holes/O2 for defect-free graphene and 0.0241 holes/O2 for graphene with STW defects. It is clear that the hole doping by O2 physisorption is enhanced by STW defects.