Depolarization effects in thin ferroelectric films

For a ferroelectric in form of a thin plate with the polarization perpendicular to the surfaces it is demonstrated that for the ferroelectric state to be stable the polarization discontinuity must be compensated by free charge. In thermal equilibrium the charge compensation can never be complete. Depolarization fields result which increase with decreasing thickness of the ferroelectric and the spontaneous polarization is reduced or becomes unstable. Internal compensation with charge in space charge layers of the ferroelectric and external compensation with charge in electrodes are discussed. Depolarization effects are shown experimentally and a first order phase transition is predicted theoretically for ferroelectrics in thin film form in contact with semiconductors in thermal equilibrium. © 1976, Taylor & Francis Group, LLC. All rights reserved.