Gas Sensors Based on Semiconducting Metal Oxides
In general, a gas sensor can be deﬁned as a device that informs about the composition of its ambient atmosphere (i.e., responds to the stimulus, Figure 22.1). More speciﬁcally, upon interaction with chemical species (adsorption, chemical reaction, and charge transfer), the physicochemical properties of the metal oxide sensitive layer (such as its mass, temperature, and electrical resistance) reversibly change. These changes are translated into an electrical signal such as frequency,
“DK3029_C022” — #2
current, voltage, or impedance/conductance, which is then read out and subjected to further data treatment and processing [1-10, 159, 160] (Figure 22.2).