Controlled defect formation and heteroatom doping in monolayer graphene using active oxygen species under ultraviolet irradiation

Abstract

The introduction of micropores, reconstruction defects, and heteroatoms into monolayer graphene has been realized by utilizing photon energy in the ultraviolet (UV) region and reactive oxygen species. The defect density of monolayer graphene has been analyzed via the Raman spectral D/G intensity ratio, and the UV emission intensity near the graphene surface has been evaluated for varying oxygen concentrations. These investigations have shown that the reactive oxygen species dissociated from ozone efficiently influence the formation of defects in monolayer graphene, which can be controlled by the oxygen concentration under UV irradiation. The effective defect formation and heteroatom doping obtained by UV irradiation have been demonstrated by scanning transmission electron microscopy with electron energy-loss spectroscopy (STEM–EELS). Finally, in defect formation due to UV irradiation under an oxygen atmosphere, it has been demonstrated that the conductivity of defective graphene is maintained at the same level as pristine graphene because defects, such as vacancy-type and reconstructed-type defects, behave as adsorption sites, resulting in a hole doping effect from oxygen atoms or molecules.