A dynamic equilibrium method for the SnO2-based ozone sensors using UV-LED continuous irradiation

We report the sensing characteristics of SnO2 thin-film gas sensors operated under room temperature. The sensor was continuously irradiated during sensing with ultraviolet (UV) light from a single 370-nm UV light-emitting diode (LED). The saturation resistance and sensitivity of the developed SnO2 sensor were observed to depend on the LED power. The SnO2 films produced a good response to ozone (O3), and this response showed good reproducibility under a dynamic O3 concentration of 5-14 ppm, and under a stable concentration. The time constant of absorption as a function of the trace O3 concentration was analyzed, and the results showed a promising correlation between time constant and concentration. The humidity affects the lowest measured resistance, but not the response. We propose the presence of a dynamic equilibrium between the background conditions to explain the working mechanism of our sensor system.