The effect of oxygen-containing reagents on the crystal morphology and orientation in tungsten oxide thin films deposited viaatmospheric pressure chemical vapour deposition (APCVD) on glass substrates

Abstract

Thin films of monoclinic WO₃ and WO_3−x have been synthesized by atmospheric pressure chemical vapour deposition from WCl₆ and three oxygen containing precursors; water, ethanol and ethanoic anhydride. A wide variation in the colour, crystal morphology and preferred orientation of the films was observed, depending on the chosen oxygen source. In particular contrast were the films formed from WCl₆ and ethanol, which were blue and had needle-like crystallites, and those formed from WCl₆ and water, which were yellow and had hexagonal shaped crystallites. Studies were also undertaken to form films from WCl₆, ethanol and water simultaneously, in which the ratio of ethanol to water was varied, and this led to films in which the crystal morphology and orientation could be controlled.