Novel Structures of Gallenene Intercalated in Epitaxial Graphene

The creation of atomically thin layers of non-exfoliable materials remains a crucial challenge, requiring the development of innovative techniques. Here, confinement epitaxy is exploited to realize 2D gallium (gallenene) via intercalation in epitaxial graphene grown on silicon carbide. Both fabrication and characterization are conducted under ultra-high vacuum conditions, unlike previous works on intercalated gallenene, to avoid gallium oxidation. Gallium is deposited on the graphene substrate via molecular beam epitaxy, and the intercalation is achieved by thermal treatments, leading to a homogeneous intercalation on almost the entire surface of the samples. Novel superstructures, including a striped and a hexagonal moiré pattern, are discovered and investigated via STM and LEED measurements. These structures arise from the interaction of gallenene with graphene and the silicon carbide substrate. The coexistence of different gallenene phases, including b010-gallenene and the unprecedented 2D-Ga(III) phase, is identified. This work sheds new light on the formation of 2D gallium and identifies a new tailored procedure for fabricating different phases of confined Ga, offering a platform for investigating the exotic electronic and optical properties of gallenene.