First-principles study of the effect of tensile strain on the electronic and optical properties of Al-doped monolayer SnS₂

The effect of biaxial tensile deformation on the optoelectronic properties of Al-doped monolayers SnS2 is explored using density functional theory. We found that the pure SnS2 monolayer is an indirect bandgap semiconductor, and with Al doping it changes to a p-type semiconductor with a lowered bandgap value. After applying biaxial tensile deformation to the doped system, i.e., with the increase of tensile strain, bandgap value decreases. Analyzing the density of states, it is found that the conduction band in a doped system is primarily made of the Sn-5s orbital and the S-3p orbital, and the valence band is primarily made of Sn-5p orbital and S-3p orbital, with the majority of S-3p orbital. The conduction and valence bands change with the rise in tensile strain, and hence the gap in the density of states close to the Fermi energy level shrinks. It is also noticed that the absorption coefficient peaks and reflection peaks of the SnS2 doped system subjected to biaxial tensile strain are blueshifted. The absorption coefficient and reflectance peaks of the doped system show a tendency to increase and then decrease with the increase of tensile strain.