Influence of Heat Treatments and Doping on the Properties of Titanium Dioxide Used in Solar Hydrogen Production

摘要

This study investigates the effect of thermal treatments on titanium dioxide (TiO_2) coatings doped with the trivalentmetallic cation chromium (Cr). Doped thin films were prepared by the co-sputtering of Ti and Cr in a closed-fieldmagnetron sputtering system. As-deposited coatings exhibited an amorphous structure; hence, post-deposition thermaltreatments were required to transform the TiO_2 into its more photoactive anatase form. This thermal transformation wascarried out using both a novel microwave plasma treatment along with conventional furnace treatments. Crystallite size,surface morphology and optical properties were all found to be dependent on the concentration of dopant within the thinfilm. Anatase crystallites, for all thermal treatments, decreased in size with increasing Cr concentration. Surfaceroughness was also observed through optical profilometry and atomic force microscopy to increase with increasing Crconcentration. A decrease in the band gap with increasing Cr concentration was seen. Microwave plasma heat treatmentswere demonstrated to be a rapid and energy-efficient method for thermally treatment of thin films.