SNO2 SENSORS - CURRENT STATUS AND FUTURE-PROSPECTS

A survey is given on the current status and future prospects in research and development of SnO2-based sensors. Atomistic models of molecular recognition are discussed first. They include physisorption, chemisorption, surface reaction, catalytic reaction, grain boundary reaction, bulk reaction and three-phase boundary reaction steps. The influence of contact geometry and crystallinity on the sensor response signal is outlined. A brief summary is given of the current status of sensor research and development with emphasis on ceramic, thick-film and thin-film sensors based on crystalline, polycrystalline and nanocrystalline SnO,. Three different aspects are mentioned in the outline which are expected to lead to significantly improved performances of future sensors: the improved selectivity through the modulation frequency in a.c. measurements, the improved stability through the better control of structures, and the improved selectivity and drift compensation through pattern recognition.