Fabrication of a \(\hbox {CO}_{2}\) Gas Sensor Based on ZnO Thin Film from the Perspective of Sensing Vehicle Tailpipe-Emitted Pollution

A zinc oxide (ZnO) thin film-based carbon dioxide (\(\hbox {CO}_{2}\)) gas sensor is proposed and designed in the present research from the perspective of sensing \(\hbox {CO}_{2}\) emissions from vehicle tailpipes. Different ZnO thin films (ZnO-TF) have been synthesized on a silicon substrate using the radio frequency sputtering technique. The characteristics of the fabricated ZnO-TFs have been analyzed by x-ray diffraction and field emission scanning electron microscopy by observing the crystalline structure and the microstructure images, respectively, of the deposited thin films. One ZnO-TF sample has been selected for electrode deposition and further electrical characterization. ZnO-TF with an interdigital electrode has shown very good characteristics while performing electrical characterization. The same device has been used for gas-sensing experiments. A portable and compact gas testing experimental setup has been designed and developed. We have used that indigenous setup to evaluate the performance of the fabricated ZnO-TF gas sensor device upon exposure to \(\hbox {CO}_{2}\) gas with varying concentrations from 1445 ppm to 4631 ppm. We mounted a reference meter (Temtop M2000 second-generation air quality monitor) on the experimental setup to measure the \(\hbox {CO}_{2}\) concentration, temperature, and humidity. Excellent sensitivity of 17.5%, 23.3%, 30.9%, 40.7%, and 47.3% was found in the fabricated sensor when exposed to \(\hbox {CO}_{2}\) concentrations of 2775 ppm, 2929 ppm, 3770 ppm, 4452 ppm, and 4631 ppm, respectively.