Effect of Electrode Shape on the Performance of ZnO-Based Ethanol Sensor

Abstract

This paper reports the deposition of Zn on glass substrates using the physical vapor deposition (PVD) method, followed by an annealing process to grow ZnO for gas-sensing applications. Surface morphologies were characterized using scanning electron microscopy, which revealed nanowire shape. The diameter of the wire was about 35 nm. In addition, X-ray diffraction analysis demonstrated that the ZnO nanowire possessed a wurtzite structure with an orientation of (002). Three types of resistive gas sensors with a spiral-square and two-comb electrode geometries were designed, fabricated, and tested for their ethanol vapor-sensing properties. The experimental results show that the sensor with square-spiral electrode has the sensitivity of 43% for 2,000 ppm of ethanol vapor at 200°C, while the sensor with a comb electrode shows the sensitivity of 32% at the same conditions. Also, two sensors with different dimensions of comb-shaped electrodes showed the same sensitivity, as both the width and the distance between the fingers change simultaneously in the larger comb-shaped electrode. The response time for the comb electrode is shorter than the square-spiral type, and the recovery time is almost independent of the electrode geometry. Therefore, the optimal structure should be selected based on the application.