Metal intercalation studies in epitaxial graphene on SiC

Abstract

Epitaxial graphene on silicon carbide (epigraphene) enables the synthesis of atomically thin heteroepitaxial crystals via the intercalation of metallic atoms at the interface between graphene and the SiC substrate. Metal intercalation involves introducing metal atoms at high temperature beneath the so-called carbon buffer layer, leading to its decoupling from the substrate. As a result, the buffer layer and the graphene atop transform into quasi-freestanding bilayer graphene. This work explores the intercalation of epigraphene with three metals: gold, indium, and bismuth, and reports the characterization results using surface science methods, Raman spectroscopy, and electron transport measurements. The lowest intercalation temperatures observed for the tested metals are T = 300 °C for indium, T = 400 °C for bismuth, and T = 840 °C for gold. The surface roughness was studied for all metals using atomic force microscopy, and the integrity of graphene was verified using Raman spectroscopy. Electron transport measurements on the heteroepitaxial films down to T = 2 K revealed that intercalation of epitaxial graphene enhances spin–orbit coupling (SOC), as evidenced by the observation of weak antilocalization corrections. Remarkably, the intercalated metals, being covered by graphene, are air-stable and allow for the fabrication of Hall bar devices using electron beam lithography. These results establish a foundation for studying enhanced SOC in engineered graphene heterostructures, with potential applications in emerging electronic devices.