Enhanced sensitivity of MoSe₂ monolayer for gas adsorption induced by electric field

According to recent studies, gas sensors based on MoSe₂ have better detection performance than graphene-based sensors, especially for N-based gas molecules, but the reason for that is not fully understood at the microscopic level. Here, we investigate the adsorption of CO, CO₂, NH₃, NO and NO₂ gas molecules on MoSe₂ monolayer by the density functional theory calculations. Our results reveal that indeed MoSe₂ monolayer is more sensitive to adsorption of N-containing gas molecules than C-containing, which can be attributed to the distinct charge transfer between the gas molecules and MoSe₂. The conductance was further calculated using the nonequilibrium Green's function (NEGF) formalism. The reduced conductance was found for NH₃ and NO₂ adsorbed MoSe₂, consistent with the high sensitivity of MoSe₂ for NH₃ and NO₂ molecules in the recent experiments. In addition, the adsorption sensitivity can significantly be improved by an external electric field, which implies the controllable gas detection by MoSe₂. The magnetic moments of adsorbed NO and NO₂ molecules can also be effectively modulated by the field-sensitive charge transfer. Our results not only give microscopic explanations to the recent experiments, but also suggest using MoSe₂ as a promising material for controlled gas sensing.