ИСТИНА

In this work we discuss the possibility of low temperature detection of NO2, CO, NH3, HCOH with light activated semiconductor gas sensors. The activation of the sensor signal under light occurs through different mechanisms. Thus, for the oxidizing gas (NO2), which compete with oxygen for the same adsorption sites, the photogeneration of electron-hole pairs plays a major role in the process of photodesorption. In contrast, to detect reducing gases (CO, NH3), the presence of chemisorbed oxygen on the surface of MOS is necessary. In this case, the light activation of sensor signal consists in the unpinning of the MOS Fermi level. For volatile organic compounds (HCOH) the photolysis of analyte molecules on the surface of MOS facilitates their subsequent oxidation with chemisorbed oxygen, leading to a change in conductivity of the semiconductor.