Characteristic temperature, semiconductor sensors

The influence of temperature on the selectivity of a sensor depends on the fact that each gas has its own characteristic temperature a temperature at which the reversible relationship between gas concentration and the concentration of electrons at the semiconductor surface (and therefore the conductance) reaches a maximum [110]. Working temperatures for Sn02-based sensors usually lie between 200 °C and 450 °C depending on the application. 

Another problem with Schottky diodes is that at high temperatures, the metal contact can anneal to the semiconductor, forming a silicide in the case of silicon and SiC [72, 80-83]. This can destroy the diode characteristic of the device, thus producing an unstable sensor. Use of an interfacial insulating layer, such as the oxide layer already mentioned, can prevent this from occurring. 

The maximum process temperature used to fabricate the organic strain sensors is 110°C. The devices were tested using a Wheatstone bridge configuration and the results indicate that it is possible to fabricate a strain sensor at low temperatures with mechanical characteristics matched to low Young modulus supports using organic semiconductors. 

Unlike metals, semiconductor materials have an inverse relationship between resistance and temperature. This characteristic is nonlinear and cannot be characterized by a linear equation such as Equation 2.9. The thermistor is a semiconductor temperature sensor. Its resistance as a function of temperature is given by... 

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