Reversible Optical Control of Polarization in Epitaxial Ferroelectric Thin Films.

Light is an effective tool to probe the polarization and domain distribution in ferroelectric materials passively, that is, non-invasively, for example via optical second harmonic generation (SHG). With the emergence of oxide electronics, there is now a strong demand to expand the role of light toward active control of the polarization. In this work, we demonstrate optical control of the ferroelectric polarization in prototypical epitaxial PbZr x Ti 1-x O 3 (PZT)-based heterostructures. we accomplish this in three steps, using above-bandgap UV light, while tracking the response of the polarization with optical SHG. First, we find that UV-light exposure induces a transient enhancement or suppression of the ferroelectric polarization in films with an upward- or downward-oriented polarization, respectively. we attribute this behavior to a modified charge screening driven by the separation of photoexcited charge carriers at the Schottky interface of the ferroelectric thin film. Second, we take advantage of this optical handle on electrostatics and accomplish remanent optical poling from a pristine multi-domain into a single-domain configuration. Third, via thermal annealing or engineered electrostatic boundary conditions, we further achieve a complete reversibility of the optical poling. Hence, our work paves the way for the all-optical control of the spontaneous polarization in ferroelectric thin films. This article is protected by copyright. All rights reserved.