Material Design for Metal Oxide Chemiresistive Gas Sensors

Conductometric gas sensors (chemiresistors) have a simple structure and their operating principle is based on the fact that their electrical conductivity (or resistance) can be modulated by the presence or absence of some chemical species that comes in contact with the device [1]. Chemiresistors consist of three elements, a sensitive conducting layer, heater and contact electrodes. These electrodes are often interdigitated and embedded in the sensitive layer. To make the measurement, a DC voltage is applied to the device and the current flowing through the electrodes is monitored as the response. The chemical species interact with the sensitive layer and thus modulate its electrical conductivity. This can be measured as a change in the current, which is correlated to the concentration of the chemical species. The main advantages of these sensors are easy fabrication, simple operation, and low production cost, which means that wellengineered metal-oxide conductometric sensors can be mass produced at reasonable cost. Moreover, these sensors are compact and durable. As a result, they are amenable to being used for in situ monitoring [1].