Theoretical study of adsorption properties and electrical transport performance of toxic gas molecules on novel orthorhombic BN monolayer semiconductor

Abstract

The adsorption properties of toxic gases on the surface of low-dimensional nanomaterials are a research hot topic and key issue for developing semiconductor sensors to detect toxic gas molecules. Recently, a novel orthorhombic BN monolayer has attracted extensive attention from researchers. Using first principles calculations, we investigate the adsorption properties of typical toxic gas molecules, such as CO, H<sub>2</sub>S, NH<sub>3</sub>, NO, NO<sub>2</sub>, and SO<sub>2</sub> molecules, on the surface of two-dimensional (2D) orthorhombic BN monolayer adsorption. The calculated adsorption energy show that the adsorptions of the above six molecules on the surface of BN monolayer are energy-favorable exothermic processes. It is found that NO<sub>2</sub> and NH<sub>3</sub> molecules are of chemical adsorption, while other systems are of physical adsorption, and NO adsorbing system exhibits a spin-polarized electronic band structure. The calculated density of states reveals that the adsorption of NO molecule and SO<sub>2</sub> molecule have significant influences on the electronic structure near the Fermi level. Moreover, the adsorption of the NO<sub>2</sub> molecule on the substrate exhibits remarkable variation of the work function, suggesting that the o-BN monolayer possesses excellent selectivity and sensitivity to NO<sub>2</sub> molecule. In addition, we use first principles combined with non-equilibrium Green’s function to simulate the electrical transport properties of monolayered o-BN semiconductor based nanodevice with adsorption of typical toxic gas molecules. The <i>I-V</i><sub>b</sub> curve shows that the current through the nanodevice is 6500 nA for the NO<sub>2</sub> molecule adsorbing system under 1 V bias voltage. The calculation results reveal that the adsorption of NO<sub>2</sub> molecule on the o-BN monolayer can significantly enhance its electrical transport performance, and the o-BN monolayer possesses excellent sensitivity and selectivity to the NO<sub>2</sub> gas molecule. The work function and the charge transfer can be effectively manipulated by tensile strain, indicating its potential application in anisotropic electronics. Our results indicate that the o-BN monolayer has excellent adsorption performance to toxic gases, showing its practical application in capturing toxic gas molecules as a gas sensor in future.