High-Sensitivity NO₂ Gas Sensor Based on Zn-Doped Indium Oxide

This study investigated the crystal structure, surface morphology, and sensing properties of Zn-doped indium oxide (IZO). IZO thin films were deposited onto a four-finger structure using RF sputtering with varying oxygen ratios to enhance sensing performance. SEM analysis revealed a petal-like structure with a preferential growth orientation along the (222) direction. In contrast, X-ray photoelectron spectroscopy analysis demonstrated surface O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub>, O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</sub>. In this study, the NO₂ detection range was 100–5000 ppb. When exposed to 1000 ppb of NO₂, the sensor exhibited a response of 9.39 (ΔR/Rair) with a response time of 22 s and a recovery time of 23 s. Compared to other gases, including H₂S, CO, H₂, and NH₃, the sensor demonstrated excellent selectivity, which can be attributed to the petal-like structure and the presence of OV and Oads. These characteristics make the sensor highly promising for applications requiring high sensitivity and selectivity in NO₂ detection.