Influence of Oxygen Vacancies in Gas Sensors Based on Metal-Oxide Semiconductors: A First-Principles Study

Despite advantages highlighted by MOX-based gas sensors, these devices still show drawbacks in their performances (e.g. selectivity and stability), so further investigations are necessary. SnO2 is the most used semiconductor for chemoresistive gas sensors production due to its broad spectrum of physical-chemical properties, and then it represents the best candidate for the innovative work here proposed. Indeed, among the gaps in research on this material, it is placed the study of oxygen deficiency and its impact on the tin dioxide physicochemical properties. A series of first-principles study was carried out in order to study the impact of oxygen vacancies on the physical-chemical properties of SnO2. The results showed a high electrical conductivity for the samples with oxygen vacancies, which can give a decrease of the operating temperature that sensing material needs to be thermo-activated. The arrangement of the impurity states is one of the important parameters that involve the reactions on the material surface, making the excitation of weakly bound valence electrons into the unoccupied energy levels in the conduction bands.