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DF: Fachverband Dielektrische Festkörper

DF 11: Ferroics - Domains, Domain Walls and Skyrmions II

DF 11.3: Vortrag

Mittwoch, 22. März 2017, 10:15–10:30, WIL B321

Early stage of ferroelectricity in BaTiO₃ multilayers — •Nives Bonacic¹, Gabriele De Luca¹, Marco Campanini², Marta D Rossell², Manfred Fiebig¹, and Morgan Trassin¹ — ¹ETH Zürich, Department of Materials — ²EMPA, Switzerland

Progress in the growth quality of transition-metal oxide heterostructures by pulsed-laser deposition greatly faciliated research of ultra-thin ferroelectrics with respect to their technological potential. In the thickness regime of a few unit cells, maintaining a large, stable and switchable ferroelectric polarization relies on the control of the strain state, thickness and interface termination in multilayers. Due to the complex interplay of these parameters, open questions remain about the intrinsic ferroelectric properties in the ultra-thin thickness regime. In order to understand the emergence of the ferroelectric polarization and determine the critical thicknesses involved, we use optical second harmonic generation (SHG) during the film deposition to probe the formation of the ferroelectric order directly. Taking (BaTiO₃-SrRuO₃)_n-based multilayers as an example, we access the polarization of each ferroelectric layer separately and of the ferroelectric interlayer coupling using SHG. Within each BaTiO₃ layer, an abrupt transition from single domain to multi-domain state is evidenced. By tracking the SHG signal during growth continuously, we show that reduced dimension and electrostatic environment induce intermediate polar states not visible in the final structure. Following the dynamics of ferroelectricity emergence and evolution in-situ paves the way to definite answers on size-reduction effects and the dynamics of complex domain formation.