Construction of rGO/WO3/SiNWs Ternary Composite Structure and Its Low-Temperature NO2 Gas-Sensing Performance

To address the issues of low sensitivity and high operating temperature in silicon nanowire (SiNWs)-based NO2 sensors, this study constructs a ternary rGO/WO3/SiNWs heterostructure by spin-coating reduced graphene oxide/tungsten oxide (rGO/WO3) composites onto SiNWs surfaces. Systematic characterizations (XRD, XPS, SEM, TEM) confirm the formation of intimate multiple p–n heterojunctions among WO3 nanorods, rGO sheets, and the SiNWs scaffold. Gas-sensing tests reveal that the rGO doping level critically modulates the sensor performance: the 0.4 wt% rGO-modified sample exhibits a sensitivity of 48.3 toward 1 ppm NO2 at 127 °C with response/recovery times of 16.4/244.8 s, while the 2 wt% rGO-modified sample lowers the optimal operating temperature to 101 °C and shortens the response/recovery times significantly to 4/184.8 s. Mechanistic analysis attributes the enhanced performance to the synergistic modulation of interfacial depletion layers and carrier transport via multiple heterojunctions among WO3, rGO, and SiNWs, in which the rGO conductive network accelerates charge transfer. This work provides an experimental basis for heterojunction engineering of high-performance, low-power NO2 sensors.