Room-temperature NO₂ sensor based on electrochemically etched porous silicon

With high-performance room-temperature gas sensors being in great demand from an energy-saving standpoint, in this study, we fabricated porous silicon (PS) sensors by electrochemically etching at different times (30, 60, and 90 min). The porous nature of the etched PSs was studied using scanning electron microscopy, and subsequently gas sensors were fabricated. NO₂ sensing studies showed that the highest gas performance can be obtained at room temperature (30 °C). Furthermore, the PS sensor etched for 60 min had the best performance among the sensors, which is related to its higher surface area and high enough initial resistance. In particular for the PS sensor etched for 60 min, the response (R_a/R_g) to 10 ppm NO₂ was 9.56, which was much higher than other interfering gases, demonstrating its high selectivity towards NO₂ gas. This study reveals the need for optimization of electrochemical etching to realize gas sensors based on PS working at room temperature.