Direct Observation of Polarization vs. Thickness Relation in Ultra-Thin Ferroelectric Films

TL;DR

This study directly observes how polarization in ultra-thin ferroelectric PbTiO3 films decreases linearly below a critical thickness of approximately 12 nm, revealing fundamental nanoscale ferroelectric behavior.

Contribution

It provides the first direct measurement of polarization versus thickness relation in ultra-thin ferroelectric films, combining experimental and theoretical approaches.

Findings

Polarization decreases linearly below 12 nm thickness

Periodic domain changes correlate with polarization reduction

Polarization and tetragonality are fundamentally linked at nanoscale

Abstract

A reduction of polarization in ultra-thin ferroelectric films appears to be fundamental to ferroelectricity at the nanoscale. For the model system PbTiO3 on SrTiO3, we report observation of the polarization vs. thickness relation. Distinct periodicity changes of ferroelectric domains obtained from x-ray diffraction and total energy calculations reveal a linear lowering of the polarization below a critical thickness of ~12 nm. Independent polarization and tetragonality measurements provide insight into the fundamental relation between polarization and tetragonality in nanoscale ferroelectrics.