Phase Transition, Stability, and Depolarization Field in Ferroelectric Thin Films

It is shown that the polarization in a thin ferroelectric film, which is sandwiched between semiconducting electrodes, is compensated incompletely. The associated depolarization fields are size dependent and change the magnitude of the polarization, transition temperature, coercive field, and the order of the phase transition. Thermodynamic considerations give stability requirements for thin films, which are different from the bulk. The properties of a thin ferroelectric film, which in bulk form exhibits a second-order phase transition, are investigated as a function of thickness, temperature, biasing potential, and electrode properties. Numerical results are presented for triglycinesulfate.