Noise analysis of metal-oxide gas microsensors response to a mixture of NO2 and CO

The noise level often limits the performances of gas sensors, particularly in terms of sensitivity. However, it can also be an effective detection tool. Indeed, noise spectroscopy is one of the solutions to enhance the selectivity and sensitivity of metal oxide sensors. This experimental technique is based on analysis of the power spectral density of noise fluctuations measured at the terminals of sensors in the presence of one or more gas. Our study focuses on physical-based analysis of low frequency noise responses in metal-oxide gas microsensors under a gas mixture composed of CO and NO₂ gases. We clearly show the existing relationship between the measured noise levels according to the type of gas in a gas mixture. The study of NO₂+CO mixture enable us to validate the models based on Langmuir and Wolkenstein theories which considers the noise generated by free electron´s density fluctuations in the sensing layer due to instantaneous fluctuations in the adsorbed molecules density.