Effect of oxygen, nitrogen and hydrogen plasma processing on palladium doped tin oxide thick film gas sensors

Tin oxide thick film sensors are widely used for detection of oxidizing and reducing gases. The conduction in tin oxide thick film gas sensor is controlled by the Schottky process through the grain boundaries due to adsorption of gas molecules on the sensor surface at elevated temperature. The barrier height is dependent on the surface state density which gets modulated due to the adsorption of different gas/odour molecules. It is likely that when such surface is treated in gaseous plasma, the surface state density may be changed permanently and response of such sensors will be affected. The experimental results obtained after annealing the sensor in different plasma shows that sensor becomes sensitive at room temperature. The results are discussed in terms of microstructure and stoichiometry of tin oxide.