Optical properties of polycrystalline and epitaxial anatase and rutile TiO ₂ thin films by rf magnetron sputtering

We analyzed successfully the refractive index n, extinction coefficient k, and optical band gap E _g of the fabricated polycrystalline and epitaxial TiO ₂ films of rutile and anatase films by spectroscopic ellipsometry (SE). The provided samples were prepared by rf magnetron sputtering of TiO ₂ target with Ar gas plasma under a variety of sputtering parameters such as total pressure, Ar gas flow rate, O ₂ gas flow rate, applied sputtering power, substrate temperature and substrate materials. The covered wavelength for SE was from 0.75 to 5eV (1653-248nm in wavelength). As the conclusion, the films show higher values of refractive indices than the previously reported ones by other authors. Optical band gaps extrapolated by Tauc plot using the obtained extinction coefficient again show higher values than the known bulk data.