Regensburg 2022 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 17: Focus Session: Surfaces and Interfaces of (Incipient) Ferroelectrics (joint session O/KFM)

KFM 17.5: Vortrag

Mittwoch, 7. September 2022, 16:30–16:45, H3

Ferroelectric domain imaging in barium titanate using infrared-visible sum-frequency generation microscopy — •Dorothee Mader¹, Daniel Lourens², Maarten Kwaaitaal², Richarda Niemann¹, Sören Wasserroth¹, Sandy Gewinner¹, Marco De Pas¹, Wieland Schöllkopf¹, Martin Wolf¹, Andrei Kirilyuk², Sebastian F. Maehrlein¹, and Alexander Paarmann¹ — ¹Fritz Haber Institute of the Max Planck Society, Berlin, Germany — ²Radboud Universiteit, Nijmegen, The Netherlands

Phonons exhibit a mostly unexplored leverage on the mechanisms and dynamics of domain formation in ferroics. Here, a new method is employed combining resonant phonon excitation and ferroelectric domain imaging of barium titanate (BTO) using infrared-visible (IR-VIS) sum-frequency generation (SFG) microscopy [1]. BTO is a non-centrosymmetric perovskite oxide with a strong ferroelectric polarization in its tetragonal phase. Typically, BTO samples exhibit a multi-domain structure. In this contribution, SFG microscopy is shown to naturally provide domain contrast due to the polarization-induced local variation of the nonlinear susceptibility. Additionally, our spectral analysis of the SFG response reveals the domain-selective phonon resonances for all high-frequency phonons in the IR spectral range of 500-800 cm⁻¹. By locally mapping phonon resonances in domains and domain walls, this approach may enable in-depth understanding of the underlying physics of domain formation and its dynamics. [1] R. Niemann et al., Appl. Phys. Lett. 120, 131102 (2022).