Electronic and optical properties of two-dimensional Janus Sn0.5Ge0.5S monolayer

Abstract

Janus two-dimensional (2D) materials have received widespread attention in recent years due to their out-of-plane asymmetric structures which makes them promising candidates for sustainable energy devices. In this work, using first-principles calculations, we study a novel 2D Janus monolayer Sn0.5Ge0.5S for recently synthesized SnS monolayer. We investigate structural, electronic and optical properties of this new 2D Janus material. Our results show that monolayer Sn0.5Ge0.5S is an indirect band gap semiconductor with the lowest conduction band is nearly flat around the band minimum. Atom projected band structure reveals that this flattened valley is mainly originated from orbitals of Sn atom. In addition, the inclusion of spin–orbit coupling leads to splitting of the bands, largely along Γ-Y direction. Optical absorption spectra indicate superior sunlight absorption in the visible and ultraviolet regions. Interestingly, absorption spectra of Janus monolayer Sn0.5Ge0.5S are polarization dependent owing to its anisotropic crystal structure along zigzag and armchair directions.