Structural, Optical and Gas Sensing Properties of Tungsten Trioxide Thin Films and Nanoparticles (original) (raw)
Tungsten trioxide (WO 3) thin films were deposited on silica, silicon and alumina substrates and their crystal structure, surface morphology, optical and gas-sensing properties were compared with those of WO 3 nanoparticles. As deposited films were amorphous and crystallized into the mon-oclinic phase with heat treatment. Raman spectroscopy revealed that the short-range structure of amorphous, crystalline films and nanoparticles of WO 3 are similar, but the amorphous phase contain W 6+ = O terminal bonds that do not exist in bulk and nanocrystalline samples. Raman studies confirmed that amorphous samples contain higher concentration of hydrogen and hydroxyl ion impurities, which affect the optical bandgap. Thin films show a response of 3 for 150 ppm of H 2 S and 7 for 2000 ppm of C 2 H 5 OH. Platelet shaped nanoparticles exhibit higher response of 37 and fast response and recovery times of 1 to 2 min for 150 ppm of H 2 S.
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