Monovalent impurities on graphene: midgap states and migration barriers

TL;DR

This paper investigates how monovalent impurities affect graphene's electronic properties and mobility, revealing stable midgap states for covalent impurities and low migration barriers for ionic impurities, with differences between anions and cations.

Contribution

It provides a detailed analysis of the electronic and migration characteristics of monovalent impurities on graphene, highlighting the stability of midgap states and the asymmetry in ionic impurity behavior.

Findings

Covalent impurities induce universal midgap states in graphene.

Migration barriers for covalent impurities are high, stabilizing midgap states.

Ionic impurities have low migration barriers (<0.1 eV) and show asymmetry between anions and cations.

Abstract

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.