Interface effects in ferroelectric PbTiO$_3$ ultrathin films on a paraelectric substrate

摘要

Interface effects on the ferroelectric behavior of PbTiO$_3$ ultrathin filmsdeposited on SrTiO$_3$ substrate are investigated using an interatomicpotential approach with parameters fitted to first-principles calculations. Wefind that the correlation of atomic displacements across the film/substrateinterface is crucial for the stabilization of the ferroelectric state in filmsa few unit-cells thick. We show that the minimum film thickness for theappearance of a spontaneous polarized domain state is not an intrinsic propertyof the ferroelectric film but depends on the polarizability of the paraelectricsubstrate. We also observe that the substrate displays an induced polarizationwith an unusual oscillatory behavior.