WO3 thin film prepared by PECVD technique and its gas sensing properties to NO2

Tungsten oxide films have been successfully fabricated from tungsten oxychloride (WOCl4) precursor by using plasma enhanced vapor deposition (PECVD) technique. The films were deposited onto silicon substrates and ceramic tubes maintained at 100°C under a constant operating pressure of He-O2 gas mixtures. The compositions and the structures of the thin films have been investigated by means of anaysis methods, such as XRD, XPS, UV and IR. The as-deposited WO3 thin films were amorphous state and became crystalline after annealing above 400°C. The surface analysis of the films indicates that stoichiometry O/W is 2.77 : 1. The gas sensing measurements of the WO3 thin film sensors indicate that these sensors have a high sensitivity, excellent selectivity and quick response behavior to NO2.