Transient and Remanent Optical Control of the Domain Configuration in Ferroelectric Epitaxial Oxide Thin Films

Light-matter interaction in ferroelectric materials forms the basis for light to be used as a non-invasive probe for the spontaneous polarization. In recent years, a shift in perspective has given rise to the question whether light could also be used to actively manipulate domain configurations or even switch the ferroelectric polarization. Realizing such an electric-field-less remote handle of the polarization holds the potential to drastically simplify state-of-the-art ferroelectric device architectures and coin entirely new ferroelectrics-based optoelectronic applications.<br/><br/>In this work, we demonstrate optical control of the ferroelectric polarization in epitaxial PZT-based heterostructures. In this prototypical ferroelectric model system, we track the dynamic response of the polarization under above-bandgap excitation by UV light in real time using optical second harmonic generation. In films with a single-domain configuration, we find that UV-light exposure induces a transient change of the spontaneous polarization that depends on its out-of-plane direction. We attribute this behavior to a modification of the charge-screening environment driven by the separation of photoexcited charge carriers in the built-in electric field of the Schottky junction formed with the bottom electrode. Taking advantage of this phenomenon in films with a pristine depolarized multi-domain configuration, we accomplish remanent optical poling into a single-domain configuration at room temperature. We further demonstrate the reversibility of this optical poling by subsequent thermal annealing. Hence, our work paves the way for the all-optical control of the spontaneous polarization in ferroelectric thin films.