The effects of adsorbed impurities on the electronic structure and gap opening in graphene

Abstract We investigate the effects of randomly distributed adatoms on the quasiparticle band structure and transport properties of graphene by combining a tight-binding model combined with large-scale Lanczos-based Green’s function calculations. Adatoms—such as hydrogen and fluorine, which preferentially bind to top sites—open a transport gap at the Dirac point that scales linearly with the square root of the impurity concentration n i m p , signaling coherent resonant scattering. A dispersionless impurity band emerges near zero energy, appearing as a sharp resonance in the density of states; its energy shift relative to the Dirac point originates from the nonzero adsorbed potential ϵ ad of adatoms. Fluorine adatoms induce a larger band gap than hydrogen at the same impurity concentration n imp , owing to their stronger hybridization coupling. These results provide a quantitative framework for interpreting angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM) data in functionalized graphene and establish design principles for disorder-engineered band-gap control.