Large-area synthesis of a semiconducting silver monolayer via intercalation of epitaxial graphene

Two-dimensional monolayers consisting of a single element have attracted considerable interest due to their intriguing properties, which can be fundamentally different from the bulk counterparts. However, their large-scale synthesis often remains challenging owing to the nonlayered nature of the respective bulk crystal structures. In this Rapid Communication we show that the noble metal silver can be confined into the monolayer limit via intercalation between silicon carbide and epitaxial buffer layer graphene. Using angle-resolved photoelectron spectroscopy we reveal the formation of a silver-related valence band whose dispersion can be described by a simple, triangular-lattice tight-binding model. Interestingly, the synthesized silver monolayer is semiconducting as opposed to the prototype $sp$ bulk metal. The intercalation process further yields an $n$-type doped quasi-free-standing graphene monolayer, thereby realizing a two-dimensional metal/semiconductor heterostructure. Our results demonstrate the potential of epitaxial graphene on silicon carbide as a functional platform for the wafer-scale synthesis of monoelemental monolayers with unique attributes.