Tuning electronic and optical properties of graphene/h-BN heterobilayer via surface modification

Herein, we have explored theoretically the effects of surface modification (fluorination) on electronic and optical properties of graphene/h-BN heterobilayer. Graphene/h-BN heterobilayer is predicted to have a semimetal characteristics. After fluorination, the heterobilayer becomes a diamane-like configuration by the interfacial atom bonding. The fluorinated graphene/h-BN (C2BNF2) has been assessed to be energetically, dynamically, and thermally stable by negative cohesive/formation energy, absence of soft mode, and intact structure at high temperature. The electronic property analysis shows that the C2BNF2 is a wide-gap direct semiconductor. Considering the photogenerated electron and hole coupling, the optical absorption spectrum of the C2BNF2 is dominated by discrete excitonic peaks, in which a large exciton binding energy beyond 1 eV is observed. The electronic and optical properties are very sensitive to the interfacial atom bonding (i.e., CB or CN bonding). Compared with the interfacial CN bonding configuration, the CB bonding configuration possesses an enhanced optical absorption for the ultraviolet light. Our results reveal that the interfacial sp3 atom bonding induced by fluorinating graphene/h-BN heterobilayer could play an important role in tuning its optoelectronic performance.