Nanostructured WO3 thin films have been prepared bythermal evaporation to detect hydrogen at low temperatures.The influence of heat treatment on the physical, chemical andelectronic properties of these films has been investigated. Thefilms were annealed at 400oC for 2 hours in air. AFM and TEManalysis revealed that the as-deposited WO3 film is highamorphous and made up of cluster of particles. Annealing at400oC for 2 hours in air resulted in very fine grain size of theorder of 5 nm and porous structure. GIXRD and Raman analysisrevealed that annealing improved the crystallinity of WO3 film.Gas sensors based on annealed WO3 films have shown a highresponse towards various concentrations (10-10000 ppm) H2 atan operating temperature of 150oC. The improved sensingperformance at low operating temperature is due to the optimumphysical, chemical and electronic properties achieved in the WO3film through annealing
