Janus HfSSe monolayer: a promising candidate for SOand COClgas sensing.

Janus monolayers based on transition metal dichalcogenides have garnered significant interest as potential materials for nano electronic device applications due to their exceptional physical and electronic properties. In this study, we investigate the stability of the Janus HfSSe monolayer usingmolecular dynamics simulations and analyze the electronic properties in its pristine state. We then examine the impact of adsorbing toxic gas molecules (AsH, COCl, NH, NO, and SO) on the monolayer's structure and electronic properties, testing their adsorption on different active sites on top of hafnium, selenium, and sulfur. The sensitivity of the gas molecules is quantified in terms of their adsorption energy, with the highest and lowest energies being observed for SO(-0.278 eV) and NO(-0.095 eV), respectively. Additionally, we calculate other properties such as recovery time, adsorption height, Bader charge, and charge difference density to determine the sensitivity and selectivity of the toxic gas molecules. Our findings suggest that the Janus HfSSe monolayer has the potential to function as SOand COClgas sensor due to its high sensitivity for these two gases.