ANGULARLY AND SPECTRALLY RESOLVED LIGHT-SCATTERING FROM LEAD-ZIRCONATE-TITANATE THIN-FILMS

The results of light-scattering measurements of a series of Pb(Zr,Ti)O -3 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 fab rication. Visual inspection of the films indicated improvements in opt ical quality with the addition of acetylacetone. To quantify these imp rovements, two types of light-scattering measurements were performed: angularly resolved light scattering and spectrally resolved light scat tering. Surprisingly, only slight differences between the films were o bserved using angularly resolved light scattering at 633 nm. In contra st, the spectrally resolved scattering revealed large differences betw een the films, with the films prepared using the largest concentration s of acetylacetone exhibiting the lowest scattering. The apparent cont radiction between these findings is resolved using a theoretical model for light scattering due to fluctuations in the dielectric constant o ccurring 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 (xi(0) = 0.08) and the characteristic size (tau(0) = 110 nm) of the dielectric constant fluctuations. These estimates are consiste nt with the variations of the dielectric constant expected due to the birefringent, polycrystalline nature of these films.