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

TL;DR

This study explores how interface interactions influence ferroelectric properties in ultrathin PbTiO$_3$ films on SrTiO$_3$ substrates, revealing that substrate polarizability and atomic displacement correlations are key to ferroelectric stability.

Contribution

It demonstrates that the ferroelectric behavior in ultrathin films depends on substrate properties and interface atomic correlations, providing insights into interface engineering for ferroelectric devices.

Findings

Atomic displacement correlation stabilizes ferroelectricity in ultrathin films.

Minimum film thickness for polarization depends on substrate polarizability.

Substrate exhibits oscillatory induced polarization.

Abstract

Interface effects on the ferroelectric behavior of PbTiO$_3$ ultrathin films deposited on SrTiO$_3$ substrate are investigated using an interatomic potential approach with parameters fitted to first-principles calculations. We find that the correlation of atomic displacements across the film/substrate interface is crucial for the stabilization of the ferroelectric state in films a few unit-cells thick. We show that the minimum film thickness for the appearance of a spontaneous polarized domain state is not an intrinsic property of the ferroelectric film but depends on the polarizability of the paraelectric substrate. We also observe that the substrate displays an induced polarization with an unusual oscillatory behavior.