Enhanced Hydrogen Sensing Response Through Controlled Porosity and Diameter of Vertically Aligned ZnO Nanorods

Abstract

We report phase pure vertically aligned zinc oxide nanorods (ZnO NRs) using a low-cost hydrothermal process on the pre-deposited RF sputtered ZnO seed layer on SiO2/Si substrate. The variation in seed layer thickness is used to control the diameter and surface porosity of ZnO NRs. The average diameter of NRs is ∼ 153, 103, and 90 nm for 2, 4, and 6-min deposited seed layers, respectively, with an average length of ∼ 3 μm irrespective of the seed layer thickness. Further, the Au/Cr interdigitated electrode is deposited on ZnO NRs/SiO2/Si to analyze its H2 sensing performance. It is observed that, among various devices, the 2 min seed layered ZnO NRs (ZNR-2) delivered superior sensing performance with 19.6% relative response, 28 s response, and 104 s recovery time, with exposure to 60 ppm H2 gas at temperature 100 . The limit of detection and limit of quantification for the ZNR-2 device is 68 ppb and 227 ppb, respectively. This device selectively responds to H2 concerning other gases. Thus, the present findings provide the guiding path for improving the sensing response for Zinc oxide-based H2 sensors.