A Light Switch for Oxide Electronics

The polarization of ferroelectric PbZr_xTi_1-​xO₃ (PZT)-​based heterostructures can be manipulated by exposure to above-​bandgap UV light. Here, the reversible transition from a fully depolarized state (multidomain at the nanoscale) to a fully polarized state (single-​domain upward-​polarized) is demonstrated. The reversibility of the optical poling is achieved via thermal annealing.

Within the frame of the SNF Spark funding, the team led by Prof. Trassin revealed that exposure to above-bandgap UV-light induces a transient enhancement or suppression of the ferroelectric polarization in PZT films with an upward- or downward-oriented polarization, respectively. This optical tunability of the ferroelectric functionality was found to be driven by a modified charge screening via the generation and separation of photoexcited charge carriers at the Schottky interface of the ferroelectric thin film. The research group subsequently took advantage of this optical handle on electrostatics and accomplished remanent optical poling from a pristine multi-domain into a single-domain configuration. A complete reversibility of the optical poling was then demonstrated via thermal annealing or by engineering of the electrostatic boundary conditions. This work, now published in Advanced Materials, paves the way for the all-optical control of the spontaneous polarization in ferroelectric thin films and opens new avenues for the integration of ferroelectric thin films into optoelectronic device and sensing schemes.