Optical constants and band gap determination of Pb0.95La0.05Zr0.54Ti0.46O3 thin films using spectroscopic ellipsometry and UV–visible spectroscopy

• Effect of annealing temperature on the optical properties of PLZT thin films was investigated.
• Correlation between annealing and grain size was confirmed.
• Grain size affected the crystallinity and band gap.
• Reflectance spectra from two spectroscopies yielded similar values of direct bandgap.
• Slight change in refractive index was observed with the change in crystallinity.

We report the structural evolution and optical properties of lanthanum doped lead zirconate titanate (PLZT) thin films prepared on Pt/TiO2/SiO2/Si substrates by chemical solution deposition. X-ray diffraction demonstrates the post-deposition annealing induced crystallization for PLZT films annealed in a temperature (Ta) range of 550–750 °C. PLZT films annealed at higher temperature exhibit polycrystalline structure along with larger grain size. Optical band gap (Eg) values determined from UV–visible spectroscopy and spectroscopic ellipsometry (SE) for PLZT films were found to be in the range of 3.5–3.8 eV. Eg decreases with increasing Ta. The optical constants and their dispersion profiles for PLZT films were also determined from SE analyses. PLZT films show an index of refraction in the range of 2.46–2.50 (λ = 632.8 nm) with increase in Ta. The increase in refractive index at higher Ta is attributed to the improved packing density and crystallinity with the temperature.