Strain Effects on the 2D van der Waals Heterostructure C₃B/C₃N: A Density Functional Theory and a Tight-Binding Study

The 2D van der Waals (vdW) heterostructure C3B/C3N is a prototype of the 2D pn junction. To understand the effects of the built-in electrical field on the properties of this heterostructure and the evolvement of properties under different strain states, the electronic structure of the system is systematically calculated and analyzed, using the first-principle method and the tight-binding (TB) Hamiltonian. Two stable structures and two saddle points in the potential surface are identified, between which the potential barriers along different sliding paths are compared. A TB model with 13 parameters is constructed, and it gives a reasonable potential difference when the heterostructure is under different strain states. Moreover, three distinct features are observed, namely the bandgap variation, metal-semiconductor transition, and band inversion under biaxial compressive strain states. By analyzing the work function change and capacitance variation, it is explained as to why the band spectrum changes as observed. This work deepens the understanding of the properties of the 2D vdW heterostructure, especially the effect of the built-in electrical field on the band spectrum.