Optical properties of tin-doped indium oxide determined by spectroscopic ellipsometry

Sputtered tin-doped indium oxide (ITO) coatings were investigated by UV-visible spectroscopic ellipsometry at different angles of incidence. The results were fitted using a classical dispersion formula for the optical constants of ITO in a model structure with a compact homogeneous film and a top layer representing surface roughness. Typical values for the high-frequency dielectric constant epsilon(x) and the plasma frequency omega(p) were found to be 3.4-4.0 and 0.68-0.96 eV, respectively. The influence of oxidative and reducing annealing at 400 degrees C was studied. No difference was observed under reducing conditions, but oxygen annealing reduced the influence of the plasma frequency on the studied UV-visible region significantly. To prove the usefulness of the dispersion formula, TiO2 and Nb2O5 films were grown on ITO by metalorganic chemical vapor deposition using Ti(acac)(2)(i-pro)(2) and Nb(OEt)(5) as precursors. These bilayers were studied by spectroscopic ellipsometry and could be successfully described applying the previously determined optical constants of ITO and a transparent Cauchy dispersion formula for the deposited oxide. (C) 1996 American Institute of Physics.