The Negative Differential Resistance Effect of Substitutional Doped Monolayer GeS and Its Application in Gas Sensor

Monolayer GeS has been demonstrated to be a potential 2-D gas-sensing material due to its high surface area and excellent stability. To explore the novel gas sensor, herein the adsorption and electronic transport properties of substitutional doped monolayer GeS toward gases CO, CO2, NH3, SO2, H2S, NO, and NO2 were investigated by using a combination of density functional theory and nonequilibrium Green’s function formalism. The band structures indicate that the doping of N atom leads to the transition of monolayer GeS from semiconductor to conductor due to the extra carries donated by dopant atom. Moreover, the adsorption capability of monolayer GeS to gas SO2 is significantly enhanced after doping the N atoms. The robust negative differential resistance (NDR) effect is obtained in the gas sensor based on N-doped GeS (N-GeS) monolayer. The selectivity and sensitivity can be verified by comparing the variations in NDR behavior of adsorbent before and after the adsorption of gases CO, CO2, NH3, SO2, and H2S. In addition, the NDR behavior can also be presented in pristine and C-doped GeS (C-GeS) monolayer with the adsorption of magnetic gas NO2. The results provide a new avenue to design the NDR-based gas sensor for detecting gases SO2, and NO2 at room temperature.