Chapter 12
Resistive Gas Sensors (Chemiresistors)
Certain kinds of conducting material experience a change in their electrical resistance in response to an interaction with gases and vapors. Among these materials, the most typical are semiconductor metal oxides and organic semiconductors. Such materials are inexpensive and resistance measurements require simple DC electronics. This prompted the development of simple and inexpensive gas sensors based on the measurement of the device resistance. The name chemiresistor is ascribed to this kind of sensor. A recent trend in this field is based on the application of various nanomaterials in chemiresistor manufacturing.
This chapter introduces the main kinds of gas-sensitive materials used in chemiresistors, the configuration of these sensors, the design principles, manufacturing methods, and applications of resistive gas sensors.
12.1 Semiconductor Metal Oxide Gas Sensors
12.1.1 Introduction
Polycrystalline semiconductor metal oxides interact with oxygen to form active oxygen species that alter the electrical charge at the grain surface. By reaction with combustible gases, oxygen active species are depleted, which results in an alteration of the resistance of the device.
Gas sensors based on semiconductor metal oxides are widely used for monitoring flammable gases (such as hydrocarbons) in industrial environment and also for detecting hazardous gases (such as carbon monoxide and nitrogen oxides) in ambient air. Such sensors are small, ...
