Very large dielectric response of thin ferroelectric films with the dead layers

Abstract

We study the dielectric response of ferroelectric (FE) thin films with the ``dead'' dielectric layer at the interface with electrodes. The domain structure inevitably forms in the FE film in the presence of the dead layer. As a result, the effective dielectric constant of the capacitor ${\ensuremath{\epsilon}}_{\mathrm{eff}}$ increases abruptly when the dead layer is thin and, consequently, the pattern of $180\ifmmode^\circ\else\textdegree\fi{}$ domains becomes ``soft.'' We compare the exact results for this problem with the description in terms of a popular ``capacitor'' model, which is shown to give qualitatively incorrect results. We relate the present results to fatigue observed in thin ferroelectric films.