Room-temperature NH3 gas sensing of S-hyperdoped silicon: Optimization through substrate resistivity

Sulfur-hyperdoped black silicon (S-BSi) prepared by femtosecond laser-assisted etching in SF6 atmosphere has dual characteristics of large specific surface area and super-doped impurities, and its physics and applications have attracted extensive attention. The room-temperature NH3 gas sensing capability of the samples is studied in the conductance mode. The S-BSi-based sensors exhibit a response to NH3 gas. Interestingly, their responsivity varies with the substrate resistance, and the sensor based on an appropriate substrate resistance shows the optimal responsivity. Additionally, the device demonstrates fast response and recovery speed, as well as good selectivity. The evolution of the responsivity and response/recovery time is recorded with natural aging for two months, showing acceptable long-term durability. The mechanism by which the responsivity of S-BSi-based sensors varies with resistivity is discussed. Based on this mechanism, there is an optimal substrate resistivity that maximizes the responsivity. The results show that S-BSi is a potential material for the fabrication of conductivity gas sensor with good NH3 detection performance.