CO2 sensing behavior of vertically aligned Si Nanowire/ZnO structures

Abstract

Metal oxide nanostructures are highly attractive for the fabrication of gas sensors due to their high surface‐to‐volume ratios. The design of novel structures has great importance to improve sensing behavior. Atomic layer deposited ZnO thin film on vertically aligned silicon nanowire (Si NW) arrays were used to understand the influence of etching time on CO2 sensing behavior of the SiNW/ZnO structure. The metal-assisted chemical etching method was used to realize SiNW arrays. The etching processes were performed for 5, 10, 30, and 60 min. The linear relationship between etching time and Si NW length was reported. 30 nm ZnO thin films were deposited on Si NWs by atomic layer deposition (ALD) method using diethyl Zinc and H2O as Zn and O2 sources, respectively. The CO2 sensing properties of the SiNW/ZnO structures were examined at ambient temperature and low CO2 concentration. The testing measurement results reveal that the sensor realized on un-etched Si does not exhibit any sensitivity. While the SiNW/ZnO was sensitive to CO2, the sensor sensitivity increase with the etching time due to the increase in the specific reactive surface. Moreover, the realized sensors have a relatively low response and recovery times, in the range of 2–7 s, by comparison to the reported ones in the literature.