Regensburg 2022 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 14: Ferroics – Domains and Domain Walls 1

KFM 14.2: Vortrag

Mittwoch, 7. September 2022, 09:50–10:10, H5

In-situ tracking of the evolution of polarization during the growth of layered-ferroelectric Aurivillius phases — •Ipek Efe, Elzbieta Gradauskaite, Manfred Fiebig, and Morgan Trassin — Department of Materials, ETH Zürich, Switzerland

The highly anisotropic nature of layered oxides is key to exotic functionalities such as superconductivity, magnetoresistance, and ferroelectricity, which are promising for applications. However, their integration in epitaxial design is challenging due to the complexity of the unit cell, which makes precise monitoring of the growth a necessity. Here, we directly access the polarization dynamics of the model system Aurivillius Bi₅FeTi₃O₁₅ films during the epitaxial growth using in-situ optical second harmonic generation (ISHG). We identify an oscillating intensity of the ISHG signal during two-dimensional layer-by-layer growth. We correlate these oscillations with the periodical evolution of the polarization of ferroelectric film dictated by the chemistry of the planes in the unit-cell, which consists of alternating positively charged fluorite-like (Bi₂O₂)²⁺ layer and negatively charged (Bi₃FeTi₃O₁₃)²⁻ perovskite blocks. In combination with reflection high-energy electron diffraction, we show how polarization of the films consistently switches from an out-of-plane orientation during the perovskite blocks growth, to a fully-in-plane orientation with the completion of the unit-cell termination and the (Bi₂O₂)²⁺ capping. Our findings reveal previously hidden polarization dynamics during the epitaxial design and bring new insights in the sub-unit cell control of layered oxide films properties for the development of energy efficient oxide electronics.