Oxidation semiconduction

In this entry, we focus on the discussion of the platform technology for electrochemical sensors, metal oxide semiconductive (MOS) sensors, and piezoelectric based quartz crystal microbalance (QCM) sensors. There are other types of chemical sensors, such as optical sensors, Schottky diode based sensors, calorimetric sensors, field-effect transistor (FET) based sensors, surface acoustic wave sensors, etc. Information of these specific sensors can be found elsewhere and in current journals on sensor technologies. Because of the increasing importance of microfabricated sensors, a brief discussion of microsensors is also given. 

Metal oxide semiconductive sensors are an important class of chemical sensors particularly for gaseous sensing. Among the metal oxide semiconductive materials. 

Metal oxide semiconductive materials exhibit a relatively low conductivity at ambient temperature. Thus, it will be very difficult to observe a small conductivity change because of its reaction with a reducing gas. Therefore, it is common to operate a MOS based sensor at elevated temperature. At higher temperature, the conductivity of the MOS increases substantially, and a change caused by the reaction with reducing gas is now observable. 

Metal oxide semiconductive sensors are not limited to tin oxide only. Many other metal oxides, such as zinc oxide, tungsten oxide, and others can also be used for chemical and gas sensing. It is understandable that an incorporation of a selective catalyst or a dopant may enhance the selectivity of the MOS sensors. Palladium, platinum, and others have been used as catalytic dopants for these sensors. The processes... 

Chapters 7-11 continue the theme and explore different types of chemical sensors. Chapter 7 describes the application of metal oxide semiconducting resistive sensors, and then Chapters 8-11 cover mainly recent developments of electrochemical sensors. 

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