Influence of substrate temperature and annealing on structural and optical properties of TiO2 films deposited by reactive e-beam evaporation

The influence of deposition and post-deposition annealing parameters on the structure and optical properties of TiO2 thin films synthesized by reactive e-beam evaporation is reported. Pure Ti (99.9%) was evaporated in oxygen atmosphere to form thin films on Si (100) and glass substrates. Depositions were conducted on substrates held at room temperature and at 200-400 °C heated substrates. Post-deposition annealing was done for 3 h at 500 °C in air. Compositional and structural studies were performed by Rutherford backscattering spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy, and optical properties were studied by ultraviolet-visible spectroscopy and analytically by pointwise unconstrained minimization approach method. It was found that both the structure and optical properties of the films are strongly influenced by the deposition and processing parameters. All deposited samples showed good stoichiometry of Ti:O ~ 1:2. Depending on the substrate temperature and oxygen pressure in the chamber during the deposition, anatase-rutile mixed films were obtained, and in some cases TiO and Ti2O3 phases were observed. Substrate deposition temperature appears to play the major role on the final structure of the films, while post-deposition annealing adds up for the lack of oxygen in some cases and invokes crystal grain growth of already initiated phases. The results can be interesting towards the development of TiO2 thin films with defined structure and optical properties.