First-principles study on the electronic structure of siligraphene on a ZnO monolayer

Abstract

Density functional theory was employed to investigate the electronic structures of atomic bilayer materials that form between graphene (g-C) or graphitic silicon carbide (also known as siligraphene: g-SiC and g-SiC2) and graphitic zinc oxide (g-ZnO). The results indicate that g-C/g-ZnO bilayers have semimetallic properties with an energy band gap of zero like in graphene. For a g-SiC/g-ZnO bilayer, an ensemble of three sp 2-hybridized carbon atoms periodically separated by three silicon atoms on g-ZnO has indirect and direct band gaps of 3.32 and 3.78 eV, respectively, which is suitable for use in light-emitting diode applications. For a g-SiC2/g-ZnO bilayer, an ensemble of four sp 2-hybridized carbon atoms periodically separated by two silicon atoms on g-ZnO has a direct band gap of 1.15 eV, which approaches the optimal value of the band gap (E opt ≃ 1.3 eV) for solar cell applications. The results show that increasing Si content in siligraphene can help to open the band gap of graphene and enhance the band gap of graphitic silicon carbide. The band gaps of siligraphene/g-ZnO bilayers depend on a smaller band gap from the monolayer component. Therefore, adjusting the Si content in siligraphene permits tuning of the band gap, and constructing a bilayer in the presence of a g-ZnO monolayer can slightly decrease the band gap. These results could lead to a new design of heterostructures with tunable band gaps for various applications.