Emergent Cavity Junction around Metal-on-Graphene Contacts.

Abstract

Harnessing graphene's electronic properties for practical applications requires a comprehensive understanding of its interfaces with metal contacts, which are essential for device integration. Traditionally, the metal-graphene (MG) interface has been considered straightforward, primarily affecting graphene's work function through doping mechanisms. However, as device dimensions shrink to the sub-micrometer scale, subtle interfacial phenomena become increasingly significant. Here, we investigate transport phenomena occurring at high-quality, sub-micrometer metal contacts on graphene. Through transport measurements, electrostatic simulations, and first-principles calculations, we demonstrate that the metal contact induces a localized n-doped radial cavity, defined cooperatively by the metal-induced electrostatic potential and Klein tunneling. This mechanism leads to quantized energy states and secondary resistance peaks as a function of graphene doping that decrease with increasing contact size. In the presence of a perpendicular magnetic field, the cavity hosts a distinct set of Landau levels, resulting in the formation of a secondary bulk interacting with the intrinsic graphene bulk. This interplay enables the direct observation of topological edge states arising from bulk-boundary correspondence. Our results provide an improved understanding of metal-graphene interfaces, highlighting fundamental properties of graphene relevant for graphene-based nanoelectronic devices.