Angularly and Spectrally Resolved Light Scattering from Lead Zirconate Titanate Thin Films

Abstract

The results of light‐scattering measurements of a series of Pb(Zr,Ti)O3 thin films prepared by a sol‐gel method are presented and analyzed. The films differed due to the addition of different concentrations of acetylacetone to the precursor solution immediately prior to film fabrication. Visual inspection of the films indicated improvements in optical quality with the addition of acetylacetone. To quantify these improvements, two types of light‐scattering measurements were performed: angularly resolved light scattering and spectrally resolved light scattering. Surprisingly, only slight differences between the films were observed using angularly resolved light scattering at 633 nm. In contrast, the spectrally resolved scattering revealed large differences between the films, with the films prepared using the largest concentrations of acetylacetone exhibiting the lowest scattering. The apparent contradiction between these findings is resolved using a theoretical model for light scattering due to fluctuations in the dielectric constant occurring within the volume of the thin film and by noting that slight thickness differences exist between the films in the series. Analysis of the light scattering from the best sample yields estimates for the amplitude (ζ0= 0.08) and the characteristic size (T0= 110 nm) of the dielectric constant fluctuations. These estimates are consistent with the variations of the dielectric constant expected due to the birefringent, polycrystalline nature of these films.