Gas Sensor Sensitivity with Current and Frequency Responses of Bifacial Porous Silicon Layer Incorporation with Tri- metallic Nanoparticles: Comparative Study

Abstract

In this work, a tri-metallic Bifacial Porous Silicon (B-PSi) sensor was fabricated and tested at room temperature to detect carbon monoxide (CO) gas. The tri-metallic (Ag, Au and Pd) nanoparticles were integrated within the (B-PSi) layers by a cheap and easy ion reduction process. The B-PSi substrate was synthesised by Double Laser-Enhanced Etching (D-LEE), with 30 mW/cm² laser illumination intensity, 17 mA.cm⁻² current density and 20 min duration. The gas sensing process in the Resistor Inductor Capacitor (RLC) circuit was represented by measuring either the resonance-frequency shift (Δf) or the current shift (ΔI) of the RLC circuit as a function of CO molecules concentration. Higher sensitivity and lower limit of detection (LOD) of 63% and 0.04 parts-per million (ppm) were obtained with frequency responses compared to 48% and 0.07 ppm obtained by current responses. Moreover, the dropping rate in the sensitivity of frequency responses was about 0.025% per day, which is lower than the current response, which was 0.083% per day. This could be related to the variation of the B-PSi capacitance. The evaluation of sensor performance via resonance-frequency shift (Δf) in impedance matching RLC circuit is a perfect and alternative choice to detect ultra-low CO concentration with small size, low power and operation at room  temperature.