Ultrahigh Sensitivity and Selectivity of Pentagonal SiC2 Monolayer Gas Sensors: The Synergistic Effect of Composition and Structural Topology

Composition and structural topology dominate the properties and functionalities of materials, especially for 2D atomic crystals, where the structure‐ and composition‐property relations are more sensitive than for their 3D counterparts. Herein, the electronic structure and transport properties of pentagonal SiC 2 (P‐SiC 2 ) monolayer with and without adsorption of typical small‐molecule gases, such as CO, CO 2 , NH 3 , NO, and NO 2 , are systemically investigated using first‐principles calculations and nonequilibrium Green's function (NEGF) method. The results show that the NO 2 molecule on P‐SiC 2 has suitable adsorption strength and apparent charge transfer compared with other molecules. Moreover, the I – V curves of P‐SiC 2 display a tremendous increase of 301% in current after NO 2 adsorption. Such ultrahigh sensitivity and selectivity to nitrogen oxides of P‐SiC 2 surpass those of graphene and penta‐graphene (PG) with isostructure. Compared with graphene and PG, the superior sensing performance of P‐SiC 2 can be attributed to the synergistic effect of composition and structural topology. This work suggests that P‐SiC 2 monolayer is a promising candidate for novel gas sensors, and tuning the structural topology and/or composition of 2D materials is an effective strategy to obtain desirable performance for nanoelectronics and optoelectronics.