Defect engineered MoSSe Janus monolayer as a promising two dimensional material for NO2 and NO gas sensing

Gas sensing mechanism of H2S, NH3, NO2 and NO toxic gases on transition metal dichalcogenides based Janus MoSSe monolayers is investigated using the density functional theory. Three types of defects (i) molybdenum vacancy, (ii) selenium vacancy, and (iii) sulfur/selenium vacancy are considered and their formation energy is computed to predict the stability. We noticed that selenium vacancy is the most stable among other defects. The maximum adsorption energy for H2S, NH3, NO2 and NO molecules on pristine Janus MoSSe monolayer are similar to - 0.156 eV, - 0.203 eV, - 0.252 eV, and - 0.117 eV, respectively. NO2 gas molecule dissociates and forms oxygen doped NO adsorption in selenium and sulfur/selenium defect included MoSSe Janus monolayer. The adsorption energy values are similar to - 3.360 eV and - 3.404 eV for Se and S/Se defects included MoSSe layer, respectively. Further, the adsorption of NO2 molecule induced about 1 mu B magnetic moment. In contrast, NO molecule showed chemisorption, whereas H2S and NH3 molecules showed physisorption with their adsorption energies in the range of -0.146 to -0.238 eV and - 0.140 to -0.281 eV, respectively. The adsorption of H2S, NH3, NO2 and NO molecule on the pristine and defected monolayers suggest that selenium and sulfur/selenium vacancy defects are more prominent for NO2 and NO gas molecule adsorption.