An investigation of the resonance frequency and current response of porous silicon sensors functionalised with tungsten oxide nanoparticles

In this investigation, a capacitive sensor based on tungsten oxide nanoparticles (WO₃_Nps) and porous silicon (Psi) hybrid structures were synthesised and extensively examined for the detection of low concentrations of NO₂ gas molecules. The integration of WO₃_Nps onto the pre-prepared Psi layers was accomplished through a cost-effective and straightforward room-temperature dipping methodology. The as-prepared Psi layers were fabricated utilising a laser-assisted electrochemical etching technique (L-AEE) at room temperature, with parameters set to 10 mW/cm² laser power, 35 mA/cm² current density, and a duration of 9 min. The frequency $\mathrm{response}{S}_f$ and current response $S_I$ of the WO_{3_}Nps/Psi hybrid structures in the RLC sensing circuit were examined at various concentrations of gas concentration. Enhanced sensitivity with a minimum DL of 51.5 % at 0.001 ppm was attained for frequency responses compared to 37.3 % and 0.02 ppm acquired through current responses.

Furthermore, the reducing rate in the sensitivity for $S_f$ was ∼ 0.022 % day^−1, which is one order of magnitude lower than that of $S_I$ which was ∼ 0.12 % day⁻¹. This variation in responses is strongly interrelated to the capacitance of the capacitance of the sensor. The evaluation of gas sensor performance in terms of $S_f$ in RLC sensing circuit represents a novel approach for the detection of lower gas concentrations.