Ferroelectric and strain-tuned MoSe/BiOSe van der Waals heterostructure with band alignment evolution.

The vertically stacked two-dimensional van der Waals heterostructure (2D vdWH) provides a unique platform for integrating distinctive properties of various 2D materials by functionalizing the interfacial interaction and regulating its band alignment. Herein, we theoretically propose a new MoSe/BiOSe vdWH material, in which a zigzag-zipper structure of the BiOSe monolayer is constructed to model its ferroelectric polarization and maintain a small interlayer mismatch with MoSe. The results show a typical unipolar barrier structure with a large band offset in the conduction band and nearly zero offset in the valence band of MoSe/BiOSe when the ferroelectric polarization of BiOSe is back to MoSe, in which the electron migration is blocked and holes can migrate unimpeded. It is also found that the band alignment lies between the type-I and type-II heterostructures and band offsets can be flexibly modulated under the joint action of ferroelectric polarization of BiOSe and in-plane biaxial tensile and compressive strains. This work would facilitate the development of multifunctional devices based on the MoSe/BiOSe heterostructure material.