Pb-intercalated epitaxial graphene on SiC: Full insight into band structure and orbital character of interlayer Pb, and charge transfer into graphene

Abstract

Intercalation is a robust approach for modulating the properties of epitaxial graphene on SiC and stabilizing two-dimensional intercalant layers at the graphene/SiC interface. In this paper, we present synchrotron-based angle resolved photoelectron spectroscopy (ARPES) measurements focusing on the band structure of intercalated Pb under a single layer of epitaxial graphene. The interlayer Pb exhibits a metallic character, a (1×1) registry with respect to SiC, and free-electron-like bands to first order. Divergences from the free-electron approximation include various band splittings and gaps throughout the Pb Brillouin zone. Light polarization-dependent ARPES measurements indicate a predominant out-of-plane orbital character for the Pb bands, suggesting potential interactions between the interlayer Pb and graphene's π orbitals that may induce proximity effects in graphene. Density functional theory calculations for a (1×1) Pb monolayer on SiC show reasonable qualitative agreement with the experimentally observed interlayer bands as well as the polarization-dependent measurements. Finally, temperature-dependent ARPES measurements reveal that the nearly charge-neutral graphene layer involves charge transfer from both the interlayer Pb and the substrate SiC. Published by the American Physical Society 2025