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.