Humidity dependence of commercial thick and thin-film MOX gas sensors under Ultra-Violet illumination

Enhancing the performance of a chemo-resistive gas sensor is often challenging due to environmental humidity influencing their sensitivity and baseline resistance. One of the most promising ways of overcoming this challenge is through Ultraviolet (UV) illumination onto the sensing material. Most research has focussed on using UV with in-house developed sensors, which has limited their widespread use. In this work, we have evaluated if UV can enhance the performance of commercially available MOX-based gas sensors. The performance of five different MOX sensors has been evaluated, specifically SGX Microtech MiCS6814 (thin-film triple sensor), FIGARO TGS2602 (n-type thick film), and Alphasense VOC sensor (p-type thick film). These sensors were tested towards isobutylene gas under UV light at different wavelengths (UV-278nm & UV-365nm) to investigate its effect on humidity, sensitivity, baseline drift and response, and recovery time of each sensor. Also, to understand the effect of UV on both thin and thick film sensors. The sensors were also tested at three different temperatures and with continuous and different blink speeds (at 2 sec, 500 sec). We found the response time of thin-film sensors for reducing gases was improved from 80 sec under dark conditions to less than 30 sec under UV- 365nm at normal operating temperatures. In addition, all the sensors were left in a dirty environment and the humid-gas testing was repeated. However, due to their robust design, the sensitivity and baseline drift of all the sensors remained the same. This indicates UV has only limited use with commercial gas sensors.