Investigation of the Effect of ZnO Film Thickness over the Gas Sensor Developed for Sensing Carbon Monoxide

Herein, a facile and inexpensive ZnO thin film‐based carbon monoxide gas sensor is fabricated using a solution‐process technique. To vary the thickness of ZnO thin films, the precursor solutions of two different molarities, 3 and 5 m, are spin coated over glass substrates. The 3 m ZnO thin‐film device demonstrates more than two times improvement in sensing response as compared to 5 m ZnO films, for 50 ppm carbon monoxide concentration. Additionally, the 3 m ZnO film is found to perform better for low carbon monoxide concentrations, whereas the 5 m ZnO film shows a linear response over a wider range of carbon monoxide concentrations. The gas sensing mechanism and the impact of film thickness on the performance of the device are thoroughly studied and discussed, which may open the doors for the design and development of facile and high‐sensitivity metal oxide‐based gas sensors.