Field, Mark Nicholas; (2002) Atmospheric pressure chemical vapour deposition of vanadium, chromium and titanium oxides. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The atmospheric pressure chemical vapour deposition of vanadium, chromium and titanium oxides has been studied. Metal halide and oxyhalide precursors were used, vanadium tetrachloride and oxychloride, chromium oxychloride and titanium tetrachloride were reacted with water and methanol, ethanol and ethyl acetate. These reactions formed vanadium oxide, chromium oxide and titanium oxide films which were deposited onto glass substrates. The APCVD reaction of VCl4 with water at temperatures above 450 C was found to result in the formation of transparent yellow V2O5 films which adhered well to the glass substrate. Below this temperature no film formation was observed. The films were found to have no chlorine contamination by XPS analysis and showed minimal photocatalytic ability. The APCVD reaction of VOCl3 showed similar results to the VCl4 / H2O system with the notable exception that film deposition was observed to occur at all temperatures above 350 C. The films were shown to have little contamination from carbon by XPS. The APCVD reaction of chromyl chloride with water was found to produce green Cr2O3 films similar in colour to bulk Cr203 powder, at temperatures above 400 C. The films showed good adherence to the glass surface with little carbon contamination by XPS. Analogous reactions between chromyl chloride and an organic solvent such as ethanol, methanol and ethyl acetate also produced Cr203 coatings. The coatings were transparent brown in colour and showed preferential growth in the 110 plane. The films showed little carbon contamination by XPS. TiO2 films were grown by the APCVD reaction of TiCl4 with water, ethanol, methanol and ethyl acetate. The major product in all reactions was the anatase form of TiO2. The thicker films had a hazy / white appearance whilst thinner films were transparent. All films adhered well to the glass surface and had low carbon contamination. The films were shown to be very effective photocatalysts. All films were analysed by Raman spectroscopy, and vis / NIR transmission reflection spectroscopy. A new APCVD system was designed and constructed to facilitate this work, described in this thesis. Further a computer program was written in order to interface the data for the vis / NIR instrumentation.

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