Gas sensing characteristics of WO3 vacuum deposited thin films

Tungsten trioxide (WO3) thin films were prepared by vacuum thermal deposition and subsequently annealed in the temperature range of 300–600 °C. X-ray diffractometry (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to analyze the structure and the morphology of the fabricated thin films. The results showed that the average grain size changed considerably with the variation of annealing temperature. Using a pair of interdigitated Au electrodes and glass ceramics as a substrate, the humidity and NO2 sensing properties of the WO3 thin films, manifested in relative conductivity changes, were measured. The results showed that the humidity sensitivity of the WO3 thin films was strongly dependent on the annealing temperature, and annealing and working temperature played an important role in the NO2 sensing characteristics.