Charge doping in graphene on thermodynamically preferred BiFeO₃(0001) polar surfaces

For graphene/ferroelectric hybrid structures, the atomistic and electronic details of the interfaces are of crucial importance for charge doping in graphene. In this paper, we choose thermodynamically stable BiFeO₃(0001) surfaces to explore the adsorption behavior and charge doping effect in a graphene/BiFeO₃ system. By performing first-principles calculations, we find that both the adsorption behavior and charge doping effect show distinct characteristics for graphene adsorbed on the oppositely polarized BiFeO₃(0001) surfaces. We predict that n-type doping and p-type charge doping occur in graphene on the positive and negative BiFeO₃(0001) surfaces, respectively. The carrier density is estimated to be 10¹³ cm^-2 orders of magnitude. Our results reveal that the graphene/BiFeO₃ hybrid system is an intriguing candidate to make graphene-based field-effect transistors, whose p-n junctions can be made by patterning the domain structure of the BiFeO₃ substrate. Moreover, the graphene/BFO hybrid structure may display an outstanding photovoltaic effect due to the combination of the bulk photovoltaic effect of the BFO substrate and the optical transparency of the graphene electrode.