Determination of gas sensing properties of thermally evaporated WO₃ nanostructures

Thin films of tungsten oxide (WO₃) nanostructures were grown on indium tin oxide coated glass substrates by thermal evaporation technique under oxygen and argon (O₂/Ar) mixed gas atmosphere. The films were characterized by X-ray diffraction, Raman spectroscopy and field emission scanning electron microscopy to study the structural and morphological properties of the grown films. Three different shapes of nanostructures (one dimensional nanorods, two dimensional nanosheets and three dimensional nanosized orthorhombic structures) were formed due to the variations of growth conditions such as substrate temperature and oxygen/argon flow rate. In particular, the flow rate of oxygen plays an important role in controlling the nucleation and growth of WO₃ nanostructures. The ethanol gas sensing properties of the films were investigated under different concentrations (10–50 ppm) at room temperature, which reveals that the sensitivity of the sensor was greatly enhanced with the increasing gas concentration. This result indicates that the WO₃ films are good candidate for sensing ethanol gas in low concentration at room temperature.