Pb(111) islands adsorbed on epitaxial graphene: a magnetotransport study

Proximity coupling is an effective approach for introducing properties into graphene that are not inherent to it. In particular, the adsorption of heavy metals can induce spin-orbit coupling (SOC) in graphene. In this study, we investigated the effects of adsorbed Pb(111) islands deposited at room temperature with an average coverage of up to 30 ML on the transport properties of monolayer graphene on SiC(0001) using magnetotransport. This investigation is supported by a structural analysis using scanning tunneling microscopy and low energy electron diffraction. The Pb(111) islands act as electron donors, increasing the electron concentration of graphene by about5×1011ML-1cm-2. Upon percolation of the Pb layer at around 5 ML, hole transport through the Pb islands had to be taken into account in order to describe the transport data. No signs of Rashba-type SOC were found, contrary to theoretical predictions for an interface between Pb(111) and graphene. Moreover, the Pb seems to screen the defects in the graphene, resulting in a reduction of the intervalley scattering rate up to 5 ML.