Homogeneous doping of epitaxial graphene by Pb(111) islands: A magnetotransport study

TL;DR

This study demonstrates that Pb(111) islands can homogeneously dope monolayer graphene without inducing Rashba spin-orbit coupling, and they also reduce defect-related scattering, providing insights into graphene functionalization.

Contribution

It shows that Pb(111) islands can uniformly dope graphene and do not induce Rashba SOC, contrasting previous results with other metals and advancing understanding of inhomogeneous doping effects.

Findings

Pb(111) islands increase electron concentration by ~5x10^{11} ML^{-1}cm^{-2}

Doping remains homogeneous despite island growth

Pb islands do not induce Rashba SOC and reduce defect scattering

Abstract

Proximity coupling is an effective approach for the functionalization of graphene. However, graphene's inertness inhibits the adsorption of closed films, thus favoring island growth, whose inhomogeneity might be reflected in the induced properties. In order to study the homogeneity of the doping profile induced by an inhomogeneous coverage and the spin orbit coupling (SOC) induced in graphene, we deposited Pb(111) islands with an average coverage of up to 30 ML on monolayer graphene (MLG) on SiC(0001) at room temperature (RT). We investigated the transport properties and the structure using magnetotransport, and scanning tunneling microscopy and low energy electron deflection, respectively. The Pb(111) islands act as donors, increasing the electron concentration of graphene by about $5\times10^{11}\;\text{ML}^{-1}\text{cm}^{-2}$. The doping was found to be homogeneous, in stark contrast to our previous results for Bi islands on MLG. Upon percolation of the Pb layer at around 5 ML, hole transport through the Pb islands has to be taken into account in order to describe the transport data. The Pb(111) islands do not induce any Rashba SOC, contrary to theoretical predictions for an interface between Pb(111) and graphene. Moreover, they seem to screen the defects in the graphene, resulting in a reduction of the intervalley scattering rate up to 5 ML.