Aligned Array of Porous Silicon Nanowires for Gas-Sensing Application

Porous silicon nanowires (SiNWs) array was prepared by a one-step metal-assisted chemical etching (MACE) method in HF/AgNO3 solution, and the potential application in gas sensor was explored. The nanowire length is found to be corrective to the etching time while the diameter and porous feature remain stable. The porous SiNWs array shows high active surface area and vertically aligned configuration favorable for gas adsorption and rapid gas diffusion. The NO2 sensing properties of the as-prepared porous SiNWs were measured at room temperature upon exposure to NO2 gas with varied concentrations. It is found that the gas sensor based on the porous SiNWs array exhibits a clear response with low noise at room temperature to extremely dilute NO2 gas as low as 50 ppb. Rapid response and recovery are achieved simultaneously owing to the highly ordered microstructure. The response time and recovery time are 5 s and 31 s for 50 ppb NO2 gas exposure, respectively. Therefore, the sensor based on the porous SiNWs array is capable of the rapid detection of NO2 gas with ppb level at room temperature. (C) 2016 The Electrochemical Society. All rights reserved.