Ferroelectric polarization rotation in order-disorder-type LiNbO3 thin films

TL;DR

This paper reports the observation of continuous ferroelectric polarization rotation in LiNbO3 thin films, achieved by controlling Li vacancies, revealing new insights into polarization behavior and symmetry breaking in ferroelectric materials.

Contribution

It demonstrates the ability to induce polarization rotation in order-disorder ferroelectric thin films through defect engineering, a novel approach in the field.

Findings

Polarization can be tilted from out-of-plane to in-plane by Li vacancy control.

Partial monoclinic-like phase indicates symmetry breaking and polarization rotation.

Continuous polarization rotation observed in LiNbO3 thin films.

Abstract

The direction of ferroelectric polarization is prescribed by the symmetry of the crystal structure. Therefore, rotation of the polarization direction is largely limited, despite the opportunity it offers in understanding important dielectric phenomena such as piezoelectric response near the morphotropic phase boundaries and practical applications such as ferroelectric memory. In this study, we report the observation of continuous rotation of ferroelectric polarization in order-disorder type LiNbO3 thin films. The spontaneous polarization could be tilted from an out-of-plane to an in-plane direction in the thin film by controlling the Li vacancy concentration within the hexagonal lattice framework. Partial inclusion of monoclinic-like phase is attributed to the breaking of macroscopic inversion symmetry along different directions and the emergence of ferroelectric polarization along the in-plane direction.