Synthesis, phase transition and optical properties of nanocrystalline titanium dioxide films deposited by plasma assisted reactive pulsed laser deposition

Titanium dioxide (TiO₂) thin films with mixed structure of anatase and rutile were deposited by oxygen plasma assisted pulsed laser deposition, and pure rutile nanocrystalline TiO₂ was obtained after post-deposition annealing. The surface morphology was examined by field emission scanning electron microscopy. The crystal structure and the crystallite size were determined using X-ray diffraction. The effects of annealing on the structural evolution and phase transition were examined by Fourier-transform infrared spectroscopy and Raman scattering spectroscopy through the analysis of bonding configurations. A progressive phase transition on annealing temperature occurs above 300°C, and a transformation to pure rutile phase completes at about 900°C. The prepared TiO₂ thin films show good transparency in the visible to near infrared region with small variations upon annealing while a red shift in band gap is observed due to annealing.