Synthesis of γ‐WO 3 thin films by hot wire‐CVD and investigation of its humidity sensing properties

In this study, monoclinic tungsten oxide (γ‐WO 3 ) have been grown in a single step using HW‐CVD method by resistively heating W filaments in a constant O 2 pressure. The formation of γ‐WO 3 was confirmed using low angle‐XRD and Raman spectroscopy analysis. Low angle‐XRD analysis revealed that as‐deposited WO 3 film are highly crystalline and the crystallites have preferred orientation along the (002) direction. HRTEM analysis and SAED pattern also show the highly crystalline nature of WO 3 with d spacing of ∼ 0.38 nm, having an orientation along the (002) direction. Surface topography investigated by SEM analysis shows the formation of a uniform and homogeneous cauliflower like morphology throughout the substrate surface without flaws and cracks. A humidity sensing device incorporating WO 3 is also fabricated, which shows a maximum humidity sensitivity factor of ∼ 3954% along with a response time of ∼14 s and a recovery time of ∼25 s. The obtained results demonstrate that it is possible to synthesize WO 3 in a single step by HW‐CVD method and to fabricate a humidity sensor by using it.