Enhancement the sensitivity and temporal response of porous silicon gas sensor via integrating gold nanoparticles

Abstract

In this research, two specific types of planner mode room temperature gas sensors involve a bare porous silicon (PS), and PS modified with gold nanoparticles PS/AuNPs were synthesized and tested extensively. The bare PS layer, was prepared by laser assisted electro chemical etching of N type (100) silicon wafer. The performance of these sensors, were studied by analyzing the FE-SEM, AFM images, XRD patterns and the gas sensing features of NO₂ at different gas concentrations from 10ppm to 40ppm. The results showed, strong modifications in sensitivity and temporal response of bare PS sensor after incorporating AuNPs. For the bare PS gas sensor, the sensitivity was 7.5% at gas concentrations of 10 ppm and 13.1% at gas concentrations of 40 ppm. While for modified AuNps/PS gas sensors, the sensitivity was increased steadily from 55.6% at gas concentration of 10ppm to 83.6% at gas concentration of about 40ppm. The as compared with the bare PS gas sensor, relationship between the sensitivity of the sensor and the gas concentration after adding gold nanoparticles is as close as possible to a linear relationship without saturation effects. The temporal response Rst and Rct of bare PS and modified (AuNps/PS) gas sensors are about 96 sec and 122 sec and for modified AuNps/PS is much lower than that of bare PS gas sensor of about 58 sec and 82 sec respectively improvement of Rst and Rct after incorporating AuNPs are about 65% and 49% respectively. This significant improvement in modified AuNps/PS gas sensor, in both of the temporal response and sensitivity is due to the thermal conductivity of AuNps and the additional surface area of AuNps to porous silicon layer. The main objective of this research is to improve the performance of gas sensors based on a porous silicon layer by incorporating gold nanoparticles. This is based on the distinct thermal properties of gold nanoparticles, as well as their high surface area. Increasing the sensitivity to detecting NO₂ gas, in addition to increasing the detection speed, is the focus of this study.