Optical properties of anatase and rutile TiO2 films deposited by using a pulsed laser.

ABSTRACT

Transparent titanium dioxide (TiO2) films were deposited on quartz substrates by using a pulsed-laser deposition technique. The effects of deposition temperatures on the crystalline phases and optical properties of the films were investigated. Phase-pure anatase and rutile TiO2 films were obtained at temperatures of 600°C and 800°C, respectively. The deposited TiO2 films were transparent in the visible spectral region, and the linear refractive indices of the films were determined by using the optical transmission spectra. The optical bandgaps were obtained as 3.25 and 3.02 eV for the anatase and rutile TiO2 films, respectively. The third-order nonlinear optical properties of the films were investigated by using a single-beam z-scan method at a wavelength of 532 nm. The values of the nonlinear absorption coefficient and the nonlinear refractive index of the rutile TiO2 film were determined to be -7.44×10-10m/W and -1.36×10-16m2/W, respectively, which are greater than those of the anatase TiO2 film. The metal-oxygen bond lengths based on the bond-orbital theory could be used to explain the results.