Adsorbates on graphene: Impurity states and electron scattering

In this review, we discuss adsorbate effects on the electronic properties of graphene. Firstly, different interaction mechanisms of impurities with graphene are introduced in terms of simple models. We discuss the requirements for impurity states in the vicinity of the Fermi level and compare graphene to normal metals and semiconductors. With this background, we consider realistic adsorbates based on density functional theory. Open-shell and inert impurities exhibit very different interaction mechanisms with graphene. The former interact directly with graphene, strongly hybridize or become charged, whereas inert impurities usually physisorb and substrate mediated doping effects become very important. (C) 2009 Elsevier B. V. All rights reserved.