Tunable electronic properties of two-dimensional type-I 1T-SN2/hBN and type-II 1T-XN2/hBN (X = Se, Te) van der Waals heterostructures from first-principle study

Abstract

Layer-by-layer integration of two-dimensional atomically thin materials provides an effective approach to the customized engineering of heteromaterials. Herein, first-principle calculations are employed to investigate the geometrical configurations and the electronic characteristics of 1T-XN2(X = S, Se, Te)/hBN van der Waals heterostructures (vdWHs). Our results demonstrate that the SN2/hBN vdWH possesses an obviously type-I band alignment. Whereas the 1T-XN2(X = Se, Te)/hBN vdWHs have a desired type-II band alignment, which may facilitate the spontaneous photogenerated electron-hole charge separation. The strain-induced semiconductor–metal transition can be realized in all the heterostructures. An intriguing type-II to type-I band alignment and indirect-direct bandgap transition takes place in 1T-TeN2/hBN under strain effect, which is a result of the different response behaviors of band-edge states with strain. The band alignment transition can be explained by the analysis of wave function topologies of band-edge states. The interlayer-coupling-tunable bandgap of 1T-XN2(X = S, Se)/hBN can also be found, and all the vdWHs always maintain their intrinsic band alignment type with the interlayer coupling effect. Overall, these findings will provide an avenue for applications of 1T-XN2(X = S, Se, Te)/hBN heterostructures in future electronic and optoelectronic devices, and strain engineering strategy can be utilized to regulate the carrier separation of the vdWHs.