SnS monolayer as gas sensors: Insights from a first-principles investigation

Using the first-principle calculations with density functional theory (DFT), we investigate systematically the adsorption of small gas molecules (CO, NH₃, SO₂ and NO₂) on monolayer SnS. The energetics, charge transfer are obtained. We determine the styles of molecule doping, and discuss the nature of interaction mechanism between gas molecules and SnS sheet. According to the calculated results, the adsorption of the specified molecules except SO₂ gas on monolayer SnS is a physisorption process with moderate adsorption energy and charge transfer, while SO₂ is chemsisorption. CO, SO₂ and NO₂ act as charge acceptors for the monolayer while NH₃ which is found to be charge donors. The results show that the sensing performance of SnS is superior to other layered materials such as graphene and phosphorene. The optical properties results exhibit that WFs could be effectively adjusted by selectively adsorbed different gas molecules. These results suggest that monolayer SnS is a promising candidate for gas sensing applications.