Spectroscopic ellipsometry study of xPbO-(1-x)TiO2 thin films elaborated by mixed reactive thermal co-evaporation

In this paper, the refractive index, extinction coefficient and optical band gap of xPbO-(1 - x)TiO2 systems are determined by spectroscopic ellipsometry in the spectral range of wavelength 250-850 nm. All films are elaborated by mixed reactive thermal co-evaporation on a SiO2/Si substrate. The Tauc-Lorentz model is used to extract the optical responses and characteristics of the layers. The best values of the fitted parameters are reported. The wavelength-by-wavelength numerical inversion, carried out without considering any fitting parameter, is also represented as another way to derive the optical constants of the layers. The refractive index and the extinction coefficient depend on the PbO content in xPbO-(1 - x)TiO2 systems. The obtained values of the optical band gap are found to change between 2.54 and 3.38 eV. It is demonstrated here that the xPbO-(1 - x)TiO2 systems with the studied compositions have an indirect optical band gap.