Determination of the Optical Properties of Sol-Gel-Derived Pb(Zr x Ti (1 − x ) )O 3 Thin Films by Spectroscopic Ellipsometry

Abstract

Optical properties of polycrystalline Pb(Zr x Ti (1 m x ) )O 3 (PZT) thin films with different Zr/Ti ratios deposited on Si(100) substrates by the sol-gel techniques have been investigated by spectroscopic ellipsometry (SE) in the UV-visible region. The measured SE spectra were fitted by a model consisting of air/roughness/PZT/substrate. The roughness was modeled using the Bruggeman effective medium approximation. The optical constants of the PZT films were parameterized using the Forouhi-Bloomer model. The refractive index n, extinction coefficient k and thickness of samples with different Zr/Ti ratios have been obtained by analyzing the SE spectra. The influence of Zr/Ti ratios on the optical properties was discussed. The optical band gap energies E g for these films were reported under the assumption of a direct band-to-band transition. It has been found that the refractive index, extinction coefficient and optical band gap energy of the films were functions of the film compositions. The refractive index of polycrystalline PZT films increase with increasing Ti content. On the other hand, the optical band gap energy of polycrystalline PZT films decreases with increasing Ti content.