Promoting sensitivity and selectivity of NO2 gas sensor based on (P,N)-doped single-layer WSe2: A first principles study

Two-dimensional transition metal disulfides(TMDs) has attracted considerable attention on gas sensor due to its excellent physicochemical properties. But the disadvantage is that the interaction between TMDs and gas is too weak, so that the response of sensor is difficult to be detected. In this study, the sensing ability of single-layer P and N atom doped WSe2 for common gases have been evaluated, including CO, SO2, H2O, NH3 and NO2. The molecular model of the adsorption systems is established, and the changes of electronic structure and adsorption behavior of the gas after doping are discussed from the binding energy, adsorption energy, band structure and density of states (DOS) by using density functional theory (DFT). The results show that dopants can improve the adsorption strength between gas molecules and substrates, among which the adsorption effect of NO2 gas molecule is the best, and the adsorption energy of WSe2 doped with single-layer P atoms is the largest. The calculation also shows that the P and N atom doped system has shorter adsorption distance and more charge transfer than the single-layer pristine WSe2. It can be inferred that single-layer N-doped WSe2 can be used as an effective, potential and highly selective NO2 gas sensor.