Semiconductor gas sensors based on nanostructured tungsten oxide

Semiconductor gas sensors based on nanocrystalline WO3 films were produced by two different methods. Advanced reactive gas evaporation was used in bot h cases either for a direct deposition of films (deposited films) or to pro duce ultra fine WO3 powder which was used for screen printing of thick film s. The deposited films sintered at 480 degreesC and the screen-printed film s sintered at 500 degreesC displayed a mixture of monoclinic and tetragonal phases and had a mean grain size of approximately 10 and 45 nm, respective ly. We studied the influence of the sintering temperature T-s of the films on their gas sensitivity. Unique and excellent sensing properties were foun d upon exposure to low concentrations of H2S in air at room temperature for both deposited and screen-printed films sintered at T-s= 480 degreesC and at T-s = 500 degreesC, respectively. (C) 2001 Elsevier Science B.V. All rig hts reserved.