Reduced work function of graphene by metal adatoms

TL;DR

This study uses density functional theory to analyze how metal adatoms reduce the work function of graphene, revealing significant decreases and electronic structure changes that depend on dopant type and concentration.

Contribution

It provides detailed insights into how different metal adatoms and their concentrations affect graphene's work function and electronic properties, with comprehensive theoretical analysis.

Findings

Work function drops significantly before saturation

Dopants prefer hollow sites on graphene

Graphene becomes metallic upon doping

Abstract

In this paper, the work function of graphene doped by different metal adatoms and at different concentrations is investigated. Density functional theory is used to maximize the reduction of the work function. In general, the work function drops significantly before reaching saturation. For example in the case of Cs doping, the work function saturates at 2.05 eV with a modest 8 % doping. The adsorption of different concentrations on metal adatoms on graphene is also studied. Our calculations show that the adatoms prefer to relax at hollow sites. The transfer of electron from metallic dopants to the graphene for all the studied systems shifts the Fermi energy levels above the Dirac-point and the doped graphenes become metallic. The value of Fermi energy shifts depends on the type of metallic dopants and its concentrations. A detail analysis of the electronic structure in terms of band structure and density of states, absorption energy, and charge transfer for each adatom-graphene system is presented.