Resumo

CASTANEDA-AVINA, L.. Gas sensors based on semiconductors. RIIIT. Rev. int. investig. innov. tecnol. [online]. 2018, vol.6, n.33. ISSN 2007-9753.

The semiconducting metal oxides (SnO2, TiO2, WO3, to mention a few) have the characteristic of modifying their electrical surface resistance when the chemical composition of the surrounding atmosphere is altered. This behavior is caused by the interaction of the metal oxide surface with the gases present in the atmosphere. According to the electronic theory of the solid state, this behavior is due to the fact that the discrete energy levels, introduced by the adsorption of oxygen, within the band of energy prohibited in the region near the surface, absorb electrons from the conduction band, generating a zone of desertion (exhaustion) and consequently a barrier of electrostatic potential on the surface of the semiconductor oxide. The creation of this region has a decisive action on the electrical properties of the material, mainly if it is thin or porous. When these materials come into contact with a reducing gas, it reacts with oxygen, physisorbed or chemisorbed, present on the surface. The reaction that occurs from the interaction between the adsorbate and the surface of the adsorbent causes a decrease in the height of the potential barrier and reduces the surface resistance of the material. Sustained in this phenomenon have been developed detectors devices of gases and vapors. A gas chemical sensor is a device having a measurable response electrical, magnetic, optical, thermal, etc., when the chemical composition of the surrounding atmosphere is altered. For the operation of chemical sensors, an extensive description of the properties and characteristics of sensors based on metal oxides gases was performed. It is expected that the importance and use of these gas sensors will increase in the immediate future due to its easy operation, small size and relatively low cost of production.

Palavras-chave : Chemisorption; dielectric; polaron; semiconductor; gas sensor.