The Influence of Mismatch-Induced Field on Thin Ferroelectric Film Size Effects

Abstract

The influence of the mismatch effect on the thin ferroelectric film properties has been studied in phenomenological theory framework. The polarization-dependent part of surface energy was expressed via surface polarization and tension tensor related to mismatch of a substrate and a film lattice constants and thermal expansion coefficients. The interfacial strain caused by the mismatch effect induces the additional surface polarization P _m via piezoelectric effect that exists near the surface in any film. P _m causes mismatch-induced thickness dependent internal electric field E _m which influences drastically all the film properties. In particular the polarization profile and hysteresis loop become asymmetrical, polarization temperature dependence resembles the one in the external electric field, and there is possibility of external field screening by the field E _m . The obtained results mak it possible to suppose that mismatch effect could be the physical reason of the ferroelectric phase conservation in ultrathin film.

Keywords:

• Surface tension
• thin film
• mismatch effect
• phase transition

ACKNOWLEDGEMENTS

We are grateful to Prof. V.M. Fridkin for the valuable remarks to our paper.