Influence of annealing temperature on nanostructured thin films of tungsten trioxide

Tungsten trioxide thin films of ~300 nm thickness have been deposited on indium tin oxide coated glass and silicon substrates by thermal evaporation technique. Influence of annealing temperature on the structural, vibrational, morphological, optical and gas sensing properties of these films has been extensively studied to search out the possible applications in opto-electronic and gas sensing devices. From the studies of optical transmittance spectra it is observed that optical band gap decreases from 3.24 to 2.72 eV with increase in annealing temperature. It is also observed that because of annealing the photoluminescence yield of the films increases. All films, especially the annealed films have shown reasonably good gas sensing behavior in acetylene environment. The film annealed at 500 °C shows better optical as well as gas sensing behaviors and hence can have good device applications.