Highly enhanced response of MoS2/porous silicon nanowire heterojunctions to NO2 at room temperature

Abstract

Molybdenum disulfide/porous silicon nanowire (MoS₂/PSiNW) heterojunctions with different thicknesses as highly-responsive NO₂ gas sensors were obtained in the present study. Porous silicon nanowires were fabricated using metal-assisted chemical etching, and seeded with different thicknesses. After that, MoS₂ nanosheets were synthesized by sulfurization of direct-current (DC)-magnetic-sputtering Mo films on PSiNWs. Compared with the as-prepared PSiNWs and MoS₂, the MoS₂/PSiNW heterojunctions exhibited superior gas sensing properties with a low detection concentration of 1 ppm and a high response enhancement factor of ∼2.3 at room temperature. The enhancement of the gas sensitivity was attributed to the layered nanostructure, which induces more active sites for the absorption of NO₂, and modulation of the depletion layer width at the interface. Further, the effects of the deposition temperature in the chemical vapor deposition (CVD) process on the gas sensing properties were also discussed, and might be connected to the nucleation and growth of MoS₂ nanosheets. Our results indicate that MoS₂/PSiNW heterojunctions might be a good candidate for constructing high-performance NO₂ sensors for various applications.