The stability of SnO2 and In2O3 gas sensors to water under temperature modulation mode

Temperature modulation technology has been extensively used in metal oxide semiconductor (MOS) gas sensors, especially based on micro-hotplate sensor structure. The technique not only enhances the selectivity but also increases the sensor’s sensitivity by allowing it to exhibit a highly active surface due to the effect of oxygen accumulation. However, when the MOS sensor is in a state of high surface activity, the corresponding hydroxide formation may occur when exposed to water, negatively affecting the gas sensing performance and stability of the sensor. This study focuses on the stability of SnO2 and In2O3 gas sensors during storage process after temperature modulation test. The results indicate that SnO2 exhibits good stability, while In2O3 stability is poor. The mechanism responsible for deactivation was discussed with infrared spectroscopy results. The formation of In(OH)3 was confirmed by high resolution transmission electron microscope, which further confirmed the above conclusion. These findings suggest that after temperature modulation, the gas sensitive materials stored in an atmospheric environment (20 ℃, 40%−60%RH) would generate hydroxides. When temperature modulation was repeated at (100–400 ℃), Sn(OH)4 decompose into SnO2, thus maintaining stability. In contrast, the decomposition temperature of In(OH)3 is higher. At 400 ℃, it will not decompose into In2O3 in a short time, which would lead to poor stability.