Optical properties of PbTiO3, PbZrxTi1-xO3, and PbZrO3 films deposited by metalorganic chemical vapor on SrTiO3

Epitaxial PbZrxTi1-xO3 (PZT) films have been prepared by metalorganic chemical vapor deposition on SrTiO3 substrates. Two sets of films of thicknesses 50-100 and 700-1400 nm, containing 0%, 40%, 60%, and 100% Zr, were prepared and investigated. The refractive index n was determined by ellipsometry for the thin films and by reflectivity for the thicker films. Results were obtained over the energy range from 1.55 to 3.72 eV, and with a Cauchy-fit extrapolation down to 0.62 eV. The refractive-index curves show a systematic variation with composition. For all compositions, n is close to 3.2 at 3.72 eV (333 nm), while at 1.55 eV (800 nm) n is 2.35 for PZ (x=1) and 2.61 for PT (x=0). In agreement with previous results we find that the optical band gap is essentially independent of composition for PZT. We obtained 3.6+/-0.1 eV. The n(E) results were analyzed by a Wemple-DiDomenico dispersion analysis, yielding results for the dispersion region in the ultraviolet. Unlike the band gap, which is insensitive to composition in PZT, the dispersion energy E-d decreases from PT to PZ in the same fashion as the refractive index in the transparent region. (C) 2002 American Institute of Physics.