Low temperature CO sensitive nanostructured WO3 thin films doped with Fe

Nanostructured tungsten oxide thin film based gas sensors have been developed by thermal evaporation method to detect CO at low operating temperatures. The influence of Fe-doping and annealing heat treatment on microstructural and gas sensing properties of these films have been investigated. Fe was incorporated in WO3 film by co-evaporation and annealing was performed at 400 °C for 2 h in air. AFM analysis revealed a grain size of about 10–15 nm in all the films. GIXRD analysis showed that as-deposited films are amorphous and annealing at 400 °C improved the crystallinity. Raman and XRD analysis indicated that Fe is incorporated in the WO3 matrix as a substitutional impurity, resulting in shorter OWO bonds and lattice cell parameters. Doping with Fe contributed significantly toward CO sensing performance of WO3 thin films. A good response to various concentrations (10–1000 ppm) of CO has been achieved with 400 °C annealed Fe-doped WO3 film at a low operating temperature of 150 °C.