Spectroscopic ellipsometry characterization of TiO2 thin films prepared by the sol–gel method

TiO2 thin films were prepared on SiO2/Si(100) substrates by the sol–gel process. XRD results indicate that the major phase of TiO2 thin films is anatase. The surface morphology and cross-section are observed by FE-SEM. The surface of thin films is dense, free of cracks and flat. The average grain size is about 60–100 nm in diameter. The thickness of single layer TiO2 thin films is about 60 nm, which increases with the concentration of solution. Ellipsometric angles ψ, Δ are investigated by spectroscopic ellipsometry. The optical constant and the thickness of TiO2 thin films are fitted according to Cauchy dispersion model. The results reveal that the refractive index and the extinction coefficient of TiO2 thin films in wavelength above 800 nm are about 2.09–2.20 and 0.026, respectively. The influences of processing conditions on the optical constants and thicknesses of TiO2 thin films are also discussed.