Structural and optical investigation of brookite TiO2 thin films grown by atomic layer deposition on Si (111) substrates

In this paper, titanium dioxide (TiO2) thin films, deposited on single crystal Si (111) substrates under different temperature conditions by Atomic Layer Deposition (ALD), have been systematically studied by X-ray diffraction, photoluminescence spectroscopy and spectroscopic ellipsometry methods. X-ray diffraction analysis showed that the prepared films have a polycrystalline brookite phase over a growth temperature range of (150-300 degrees C). Increasing the growth temperature resulted in systematic increase of texturing the polycrystalline grains along the (200) direction, with the film at 300 degrees C having the highest textur along the (200) direction. This was accompanied by improved photoluminescence of the TiO2 films with the increasing the growth temperature. The improved crystallinity at higher temperatures was also reflected by higher refractive indices, which were deduced from spectroscopic ellipsometry measurements carried out on the grown films.