Engineering Graphene Work function by Changing Metal Adatoms and their Concentrations*

Graphene is one of the thinnest material to date, consisting of a single layer of carbon atoms arranged in aromatic rings forming a honeycomb-like structure. Doping graphene is of current research interests, aiming at improving and manipulating the electronic properties and work function of graphene through metal atom adsorption. In this work, we present a reduction of graphene work function by using different metal adatoms and their concentration. All the studied metal-doped graphene show a reduction of work function. However, the reduction varies for each metal and its concentration. In the case of Cs and Rb doped graphene, maximum work function reductions of 2.05 and 2.18 eV ¹ respectively are obtained. Due to doping, the adatoms induce crucial changes in the electronic structure of graphene. The transfer of electrons from the adatoms to graphene shifts up the Fermi level. Consequently, normally semi-metallic graphene becomes metallic with a significant density of states at the Fermi level. In this work, we will present a detailed analysis of the electronic structure, absorption energy, and charge transfer for each adatom-graphene system.
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