Bandgap engineering of two-dimensional C₃N bilayers

Carbon materials such as graphene are of potential use in the development of electronic devices because of properties such as high mechanical strength and electrical and thermal conductivity. However, technical challenges, including difficulties in generating and modulating bandgaps, have limited the application of such materials. Here we show that the bandgaps of bilayers of two-dimensional C₃N can be engineered by controlling the stacking order or applying an electric field. AA′ stacked C₃N bilayers are found to have a smaller bandgap (0.30 eV) than AB′ stacked bilayers (0.89 eV), and both bandgaps are lower than that of monolayer C₃N (1.23 eV). The larger bandgap reduction observed in AA′ stacked bilayers, compared with AB′ stacked bilayers, is attributed to the greater p_z-orbital overlap. By applying an electric field of ~1.4 V nm⁻¹, a bandgap modulation of around 0.6 eV can be achieved in the AB′ structure. We also show that the C₃N bilayers can offer controllable on/off ratios, high carrier mobilities and photoelectric detection capabilities.