One step process for chemical vapour deposition of titanium dioxide thin films incorporating controlled structure nanoparticles

In this work we describe a two stage chemical-vapour-deposition based route to growing nanoparticle containing thin films. As a model we describe titanium dioxide film formation on glass substrates. The process involves using a gas-to-particle conversion method, to first form the particles, and then a conventional atmospheric pressure chemical vapour deposition (APCVD) reactor has been used to assemble the particles onto the glass substrates through a combination of thermophoresis and diffusion. The gas-to-particle method imparts a high degree of control over the particle size and structure, i.e. crystallinity and size distribution, which when combined with APCVD offers a route to structure and composition controlled thin films. The photocatalytic properties of the resulting nanoparticulate films have been evaluated and compared against those for continuous titanium dioxide films grown using conventional APCVD. Films have been evaluated using X-ray diffraction, scanning electron microscopy and photoactivity testing (stearic acid decomposition). The results are discussed in terms of possible uses of the nanoparticulate films themselves, and also the possibility of incorporating nanoparticles directly into APCVD grown films.