Ferroelectric and strain-tuned MoSe₂/Bi₂O₂Se 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 MoSe₂/Bi₂O₂Se vdWH material, in which a zigzag-zipper structure of the Bi₂O₂Se monolayer is constructed to model its ferroelectric polarization and maintain a small interlayer mismatch with MoSe₂. 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 MoSe₂/Bi₂O₂Se when the ferroelectric polarization of Bi₂O₂Se is back to MoSe₂, 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 Bi₂O₂Se and in-plane biaxial tensile and compressive strains. This work would facilitate the development of multifunctional devices based on the MoSe₂/Bi₂O₂Se heterostructure material.