Effect of vacancy defects of SnS on gas adsorption and its potential for selective gas detection

SnS is a two-dimensional black phosphorus-like material with potential in gas sensor applications. The vacancy defects generally existed in SnS structure could show a marked impact on its surface, physicochemical and electronic properties. This work focuses on the effect of vacancy defects in SnS, including S-vacancy and Sn-vacancy, on its gas adsorption and selectively sensing characteristics. To this end, we carry out first-principles calculations on vacancy-defected SnS and corresponding adsorption configurations with different gas molecules. Adsorption energy, density of states and Mulliken population for pristine SnS and defective SnS respectively with S-vacancy and Sn-vacancy were calculated and analyzed to clarify the correlation of adsorption characteristic with surface structure. The results revealed that the presence of S-vacancy in SnS creates a preferring surface for NH3 adsorption, while the defective SnS with Sn-vacancy is capable of enhanced adsorption and selective detection for NO2. For CH2O, CO, H2S and CH4, weak adsorption and low sensitivity are demonstrated to occur on SnS and defective SnS according to the adsorption energy calculations. The adsorption difference of the defective SnS with S- and Sn-vacancy towards NH3 and NO2 gases is deeply clarified by analyzing the charge density difference of corresponding defective structure.