Impurity resonance effects in graphene versus impurity location, concentration, and sublattice occupation

Unique electronic band structure of graphene with its semimetallic features near the charge neutrality point is sensitive to impurity effects. Using the Lifshitz and Anderson impurity models, we study in detail the disorder induced spectral phenomena in the electronic band structure of graphene, namely, the formation of resonances, quasigaps, bound states, impurity subbands, and their overall impact on the electronic band restructuring and the associated Mott-like metal-insulator transitions. We perform a systematic analytical and numerical study for realistic impurities, both substitutional and adsorbed, focusing on those effects that arise from the impurity adatoms locations (top, bridge, and hollow positions), concentration, unequal occupations of the graphene host sublattices, perturbation strengths, etc. Possible experimental and practical implications are discussed as well.