Doping of graphene by a Au(111) substrate: Calculation strategy within the local density approximation and a semiempirical van der Waals approach

TL;DR

This study uses density functional theory to analyze how the Au(111) substrate dopes graphene, showing that doping levels depend on computational methods and structural parameters, with implications for electronic device applications.

Contribution

It introduces a detailed analysis of doping effects in graphene on Au(111) using both LDA and semiempirical van der Waals approaches, highlighting the influence of structural parameters.

Findings

Graphene on Au(111) remains mostly undoped or slightly p-type doped.

Small changes in substrate parameters can switch doping from p-type to n-type.

Structural tuning can control doping levels for device applications.

Abstract

We have performed a density functional study of graphene adsorbed on Au(111) surface using both a local density approximation and a semiempirical van der Waals approach proposed by Grimme, known as the DFT-D2 method. Graphene physisorbed on metal has the linear dispersion preserved in the band-structure, but the Fermi level of the system is shifted with respect to the conical points which results in a doping effect. We show that the type and amount of doping depends not only on the choice of the exchange-correlation functional used in the calculations, but also on the supercell geometry that models the physical system. We analyzed how the factors such as the in-plane cell parameter and interlayer spacing in gold influence the Fermi level shift and we found that even a small variation in these parameters may cause a transition from p-type to n-type doping. We have selected a reasonable set of model parameters and obtained that graphene is either undoped or at most slightly p-type doped on the clean Au(111) surface, which seems to be in line with experimental findings. On the other hand, modifications of the substrate lattice may induce larger doping up to 0.30-0.40 eV depending on the graphene-metal adsorption distance. The sensitivity of the graphene-gold interface to the structural parameters may allow to tune doping across the samples which could lead to possible applications in graphene-based electronic devices. We believe that the present remarks can be also useful for other studies based on the periodic DFT.