Physical properties of novel Tin-chalcogenides heterostructures: A first-principles study

In recent years, the van der Waals (vdW) Heterostructures (HTSs) are broadly studied for their capabilities to modulate the performance of two-dimensional (2D) materials. Herein, we constructed four types of vdW HTSs by vertically stacking the alpha-polytype and delta-polytype of single-layered SnS and SnSe. The constructed HTSs have been designated as HTS-I (SnS(alpha)/SnS(delta)), HTS-II (SnSe(alpha)/SnSe(delta)), HTS-III (SnS(alpha)/SnSe(delta)), and HTS-IV (SnSe (alpha)/SnS(delta)) and their physical properties are systematically explored by the first-principles approach. The electron density mapping revealed that the monolayers constituting these HTSs are stacked by vdW coupling which persists for interlayer distance (Delta y) up to similar to 7 angstrom. However, these tin-chalcogenide-based HTSs demonstrated the highest formation energies (E-f) and binding energies (E-b) for Delta y =similar to 3.75 angstrom. The electronic structure calculations revealed them as semiconductors of indirect bandgaps of magnitude 1.22, 1.28, 1.06, and 1.22 eV recorded for HTS-I, HTS-II, HTS-III, and HTS-IV, respectively. They exhibited type-II (staggered) band alignment where the valence band maximum occurs in the delta-type of monolayer and the conduction band minimum is located in alpha-type of monolayers that causes the splitting of the photo-generated electron-hole pairs at the interface. Therefore, the staggering gap and large density of states observed near the bandgap edges have triggered a significantly improved optical absorption in these HTSs compared to freestanding monolayers. Moreover, the transparent nature of these HTSs has been recognized against incident light of energy less than 5 eV. These predictions illustrate the development of vdW HTSs as an effective approach to improve the functionalities of 2D materials for advanced technological applications.

Automated summary

In recent years, researchers have extensively studied van der Waals (vdW) heterostructures (HTSs), constructing four types of vdW HTSs by vertically stacking different polytypes of single-layer SnS and SnSe. These HTSs are stacked through vdW coupling and have high formation and binding energies. They are found to be indirect bandgap semiconductors, with significantly improved optical absorption due to the splitting of electron-hole pairs at the interface. These predictions demonstrate the potential applications of vdW HTSs in enhancing the functionalities of 2D materials.