Monolayer SnS as a superior sensor for O3 and NO gases: a DFT-NEGF study

Two-dimensional materials are suitable candidates for gas sensor applications, due to their high surface-to-volume ratio, fast response and strong interaction between their surface and adsorbate molecules which leads to the significant charge transfer. In this work, using first-principles calculations based on density functional theory, we investigate the most stable adsorption configurations of , , , , , and molecules on the surface of monolayer SnS. The results show the highly reactive molecule and the two paramagnetic molecules ( and ) exhibit higher adsorption energies and greater charge transfer compared to , , and , acting as charge acceptors on the SnS monolayer surface. Also, it is observed that these adsorbate molecules dramatically alter the density of states of monolayer SnS near the Fermi level. In the following, by using the density functional theory in combination with the nonequilibrium Green’s function (NEGF), we calculate and explore the current-voltage (I-V) characteristic curves of monolayer SnS with and without adsorption of and molecules along the armchair and zigzag directions. Different transport and sensing properties are found in armchair and zigzag directions owing to the anisotropic crystal and electronic structure of monolayer SnS along these directions, which provides an additional parameter to optimize the gas sensor performance. Moreover, the results of calculations for SnS monolayer predict a high sensitivity and strong selectivity for and molecules detection. Interestingly, in the case of adsorption, the passing current and transmission spectra are slightly spin-polarized, particularly along the armchair direction.