Interface controlled band alignment type in Janus SnS2/SSnSe and SnS2/SeSnS van der Waals heterojunctions

Two-dimensional (2D) Janus structures have been employed significantly considering their asymmetrical layout and multiple applications in different areas. A novel van der Waals (vdW) heterojunction is constructed based on the SnS2 monolayer and Janus SnSSe monolayer in the current study. Due to different atoms in two sides of the SnSSe monolayer, two kinds of heterojunctions, including SnS2/SSnSe and SnS2/SeSnS, can be constructed. Both heterojunctions are indirect band gap semiconductors. The kind of interface atom can affect the electronic properties of heterojunctions, resulting in interface-controlled band alignment (BA) type. Since the conduction band minimum states of the SnS2/SSnSe system contain the contribution of both SSnSe and SnS2 layers, this system is not suitable for efficient electron-hole separation. The SnS2/SeSnS heterojunction constructs a standard type-II BA, in which the holes and electrons are placed within the layers of SeSnS and SnS2, respectively. The external electric field, in-plane strain, and the adsorption of nonmetal atoms are also considered to modulate the electronic properties and BA type of the heterojunctions. According to these findings, the interface atom is an important factor influencing the electronic properties of those Janus vdW heterojunctions.