The Dependence of the Effective Dielectric Constant of PbTiO 3 on the Surface Layer

Complex oxide thin films, such as ferroelectric thin films, are being widely used in various devices. However, the chemical composition and chemical bondings of the surface layer are usually different from those in the "bulk" region of the oxide thin films. The existence of the surface layer will certainly affect the properties, such as dielectric behavior, of the films. Departing from the effective medium theory, the dependence of the effective dielectric behavior of PbTiO 3 thin films on the surface layer has been analyzed by using the model we proposed. The effective dielectric constant of the thin film is proposed as the function of the dielectric constants of the expected compounds and the unexpected compounds in the surface layer, the content of the unexpected compounds compared with the expected compound in the surface layer, and the volume faction of the surface layer in the whole thin films. The surface layer deviating stoichiometry has a pronounced effect on the effective dielectric constant of the thin films.