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 pz-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. The bandgaps of bilayers of two-dimensional C3N can be modulated by controlling the stacking order of the layers or by applying an electric field.