Atomically-precise fabrication and characterization of oxygen substitutions in graphene

The atomically precise engineering of defects and impurities in graphene, along with an understanding its doping-dependent electronic properties, is essential for the advancement of graphene-based electronics. Here we present a method for the controlled incorporation of the oxygen (O) substitutions into epitaxial graphene grown on the SiC(0001) substrate and investigate their atomic-scale characteristics. We utilize a combination of chemical-bond-resolved non-contact atomic force microscopy (ncAFM), scanning tunneling microscopy and spectroscopy (STM/S), augmented by density functional theory (DFT) and Tight Binding (TB) calculations to examine the structural and electronic properties of the O-related substitutions. Bond-resolved ncAFM measurements confirm the formation of elusive sp²-hybridised O dopants, while STM/S reveals their distinctive electronic state near the Dirac point, which remains rigidly pinned to the Dirac point across various charge carrier doping regimes. Our findings demonstrate a novel approach for the controlled formation of O-related substitutions in graphene and establish their atomic-scale structure-property relationships.