Abstract
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.
Highlights
Two-dimensional (2D) materials are a current focus of condensed matter physics [1,2] due to their unique properties which are absent in the bulk homologs and make them promising candidates for, e.g., next-generationelectronics and catalysis [3,4,5]
The large-scale epitaxy of monoelemental monolayers (MLs) typically requires delicate procedures owing to the nonlayered bulk crystal structures [6]
Besides the dominant π bands of quasi-free-standing (QF) monolayer graphene (MLG) near KGr, one additional band can clearly be discerned. It disperses through a maximum 0.59 ± 0.03 eV below the Fermi level EF and a saddle point at a binding energy of E = 1.60 ± 0.03 eV until merging with the silicon carbide (SiC) bulk bands around normal emission. Such a feature is absent in pristine ZLG [35], MLG [36], as well as QFMLG decoupled via hydrogen intercalation [19] and must be related to the intercalated silver
Summary
Two-dimensional (2D) materials are a current focus of condensed matter physics [1,2] due to their unique properties which are absent in the bulk homologs and make them promising candidates for, e.g., next-generation (opto)electronics and catalysis [3,4,5]. The large-scale epitaxy of monoelemental monolayers (MLs) typically requires delicate procedures owing to the nonlayered bulk crystal structures [6]. Few such materials beyond graphene have so far been realized [7,8,9,10,11,12]. Epitaxial graphene on SiC might be an ideal platform for the scalable synthesis of various monoelemental MLs with distinct electronic structures. To highlight this general potential the spectrum of available materials should be extended.
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