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 make it possible to suppose that mismatch effect could be the physical reason of the ferroelectric phase conservation in ultrathin film.

Phase composition and crystallinity of thin lead titanate films

“…Nevertheless, partially the substrate effect can be explained by the difference of thermal expansion of materials and, consequently, by the occurrence of strong mechanical stresses in the film. 5 Effects of a substrate and grain boundaries Practically all theoretical works devoted to this subject, are based on the phenomenological consideration of Landau-Ginzburg-Devonshire [6][7][8]. Revealing of polarization distribution over a volume of a film grain seems one of the key issues.…”

“…Revealing of polarization distribution over a volume of a film grain seems one of the key issues. The distribution of polarization for thin polycrystalline lead titanate films consisting of Me/PbTiO 3 /Pt/substrate structure has been constructed on the basis of the analysis of experimental and theoretical works of other authors [6][7][8][9][10]. The systematic result is presented in Fig.…”