Gas-Sensing Properties of the SiC Monolayer and Bilayer: A Density Functional Theory Study.

Using density functional theory calculations, the adsorption of gaseous molecules (NO, NO(2), NH(3), SO(2), CO, HCN, O(2), H(2), N(2), CO(2), and H(2)O) on the graphitic SiC monolayer and bilayer has been investigated to explore the possibilities in gas sensors for NO, NO(2), and NH(3) detection. The strong adsorption of NO(2) and SO(2) on the SiC monolayer precludes its applications in nitride gas sensors. The nitride gases (NO, NO(2), and NH(3)) are chemisorbed on the SiC bilayer with moderate adsorption energies and apparent charge transfer, while the other molecules are all physisorbed. Further, the bilayer can effectively weaken the adsorption strength of NO(2) and SO(2) molecules, that is, NO(2) molecules are only weakly chemisorbed on the SiC bilayer with an E (ads) of -0.62 eV, while SO(2) are physisorbed on the bilayer. These results indicate that the SiC bilayer can serve as a gas sensor to detect NO, NO(2), and NH(3) gases with excellent performance (high sensitivity, high selectivity, and rapid recovery time). Moreover, compared with other molecular adsorptions, the adsorption of NH(3) molecules significantly changes the work function of the SiC monolayer and bilayer, indicating that they can be used as optical gas sensors for NH(3) detection.