Enhanced room-temperature NO₂ sensing via abundant edge interfaces on graphene oxide-decorated silicon

Abstract

NO₂ gas sensing properties of the graphene oxide-decorated silicon (GO/Si) materials with abundantly exposed edge interfaces are studied. GO sheets are intermittently covered on the silicon surface treated with hydrophilic agents through a spin-coating process, enabling the formation of a sensing layer with optimized active surface area and diversified adsorption sites, which facilitate gas sensing. As the sensitive material in a conductometric gas sensor, far different from the respective planar Si and pristine GO, which exhibit poor repeatability and an undesirable n- to p-type response transition, the GO/Si brings about a qualitative change in sensing behavior, showing consistent p-type response to all tested concentrations and exhibiting good reproducibility. More interestingly, the coverage of GO can be simply adjusted by the hydrophilic treatment time. At an optimal hydrophilic treatment time ∼ 1 second, the GO/Si sensor demonstrates an ultra-low theoretical detection limit of 188 ppt, along with high response, good selectivity, and long-term stability. The mechanisms behind the outstanding sensing performance are discussed, considering the exposed GO/Si edge interface and the synergistic effect of GO and Si.