Monovalent impurities on graphene: midgap states and migration barriers

Monovalent impurities on graphene can be divided into ionically and covalently bond impurities. The covalent impurities cause universal midgap states as the carbon atom next to the impurity is effectively decoupled from the graphene pi-bands. The electronic structure of graphene suppresses migration of these impurities and making the universal midgap very stable. This effect is strongest for neutral covalently bond impurities. The ionically bond impurities have migration barriers of typically less than 0.1eV. An asymmetry between anions and cations regarding their adsorption sites and topology of their potential energy landscape is predicted.