Hybrid graphene and graphitic carbon nitride nanocomposite: Gap opening, electron-hole puddle, interfacial charge transfer, and enhanced visible light response

Opening up a band gap and finding a suitable substrate material are two big challenges for building graphene-based nanodevices. Using state-of-the-art hybrid density functional theory incorporating long-range dispersion corrections, we investigate the interface between optically active graphitic carbon nitride (g-C₃N₄) and electronically active graphene. We find an inhomogeneous planar substrate (g-C₃N₄) promotes electron-rich and hole-rich regions, i.e., forming a well-defined electron-hole puddle, on the supported graphene layer. The composite displays significant charge transfer from graphene to the g-C₃N₄ substrate, which alters the electronic properties of both components. In particular, the strong electronic coupling at the graphene/g-C₃N₄ interface opens a 70 meV gap in g-C₃N₄-supported graphene, a feature that can potentially allow overcoming the graphene's band gap hurdle in constructing field effect transistors. Additionally, the 2-D planar structure of g-C₃N₄ is free of dangling bonds, providing an ideal substrate for graphene to sit on. Furthermore, when compared to a pure g-C₃N₄ monolayer, the hybrid graphene/g-C₃N₄ complex displays an enhanced optical absorption in the visible region, a promising feature for novel photovoltaic and photocatalytic applications.