Fabrication of tungsten oxide nanostructured films using anodic porous alumina and application in gas sensing

Abstract

In this thesis, we examine the suitability of using anodic porous alumina as a supporting substrate for creating a textured metal oxide semiconducting (MOX) nanofilm to be used as a gas sensor in argon ambient. A chemical vapour deposition (CVD) system for CVD of tungsten is designed and set up. The textured film is deposited using low pressure chemical vapour deposition (LPCVD) of tungsten using the CVD system. The film is then thermally oxidized to form a sub-stoichiometric tungsten oxide film. A measurement system that can be used to characterize a gas-sensing device is designed and setup as well. Comparisons of oxygen and ammonia sensing characteristics are made between the textured film deposited on porous alumina and that of a thin film deposited on glass substrate using the measurement system. It is found that the thin film sensor performed better than the textured film sensor. Possible explanations for the observed gas sensing characteristics are given.