Electronic doping of graphene by deposited transition metal atoms

TL;DR

This paper presents a phenomenological model explaining how transition metal atom clusters doped on graphene influence its electronic properties, including doping levels and resistivity, aligning with experimental observations at low coverages.

Contribution

It introduces a model that links chemical interactions and scattering effects of metal clusters on graphene's electronic behavior, explaining experimental results and deviations at higher coverages.

Findings

Model explains doping levels and ionization potentials.

Resistivity contributions from metal clusters are quantified.

Deviations at higher coverages are theoretically justified.

Abstract

We perform a phenomenological analysis of the problem of the electronic doping of a graphene sheet by deposited transition metal atoms, which aggregate in clusters. The sample is placed in a capacitor device such that the electronic doping of graphene can be varied by the application of a gate voltage and such that transport measurements can be performed via the application of a (much smaller) voltage along the graphene sample, as reported in the work of Pi et al. [Phys. Rev. B 80, 075406 (2009)]. The analysis allows us to explain the thermodynamic properties of the device, such as the level of doping of graphene and the ionisation potential of the metal clusters in terms of the chemical interaction between graphene and the clusters. We are also able, by modelling the metallic clusters as perfect conducting spheres, to determine the scattering potential due to these clusters on the electronic carriers of graphene and hence the contribution of these clusters to the resistivity of the sample. The model presented is able to explain the measurements performed by Pi et al. on Pt-covered graphene samples at the lowest metallic coverages measured and we also present a theoretical argument based on the above model that explains why significant deviations from such a theory are observed at higher levels of coverage.