Impurity and vacancy effects in graphene

Abstract

A Green function analysis is developed for the quasiparticle spectrum of 2D graphene sheets with different types of substitutional disorder, including vacancies. Impurity effects in this system are found to be anomalous, are compared to those in well-known doped semiconductors, and are explained in terms of conical singularities in the band spectrum of pure graphene. Criteria for the appearance of localized states on clusters of impurity scatterers and for qualitative restructuring of the band spectrum are established and the possibility of a distinctive metal/insulator transition when vacancies are present is discussed.