Electrostatically Driven Polarization Flop and Strain-Induced Curvature in Free-Standing Ferroelectric Superlattices

Yaqi Li; Edoardo Zatterin; Michele Conroy; Anastasiia Pylypets; Fedir Borodavka; Alexander Björling; Dirk J Groenendijk; Edouard Lesne; Adam J Clancy; Marios Hadjimichael; Demie Kepaptsoglou; Quentin M Ramasse; Andrea D Caviglia; Jiri Hlinka; Ursel Bangert; Steven J Leake; Pavlo Zubko

doi:10.1002/adma.202106826

Electrostatically Driven Polarization Flop and Strain-Induced Curvature in Free-Standing Ferroelectric Superlattices

Adv Mater. 2022 Apr;34(15):e2106826. doi: 10.1002/adma.202106826. Epub 2022 Mar 1.

Authors

Yaqi Li¹, Edoardo Zatterin^{1

2}, Michele Conroy^{3

4

5}, Anastasiia Pylypets⁶, Fedir Borodavka⁶, Alexander Björling⁷, Dirk J Groenendijk⁸, Edouard Lesne⁸, Adam J Clancy⁹, Marios Hadjimichael¹⁰, Demie Kepaptsoglou^{11

12}, Quentin M Ramasse^{11

13}, Andrea D Caviglia⁸, Jiri Hlinka⁶, Ursel Bangert⁴, Steven J Leake², Pavlo Zubko^{1

5}

Affiliations

¹ Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, UK.
² ESRF, The European Synchrotron, 71 Avenue des Martyrs, Grenoble, 38000, France.
³ Department of Materials, Imperial College London, Exhibition Road, London, SW7 2AZ, UK.
⁴ Department of Physics, Bernal Institute, University of Limerick, Limerick, V94 T9PX, Ireland.
⁵ London Centre for Nanotechnology, 17-19 Gordon Street, London, WC1H 0HA, UK.
⁶ Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, 18221 Praha 8, Czech Republic.
⁷ MAX IV Laboratory, Lund, SE-221 00, Sweden.
⁸ Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, Delft, GA 2600, The Netherlands.
⁹ Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK.
¹⁰ Department of Quantum Matter Physics, University of Geneva, Geneva, 1211, Switzerland.
¹¹ SuperSTEM Laboratory, SciTech Daresbury Campus, Daresbury, WA4 4AD, UK.
¹² Department of Physics, University of York, York, YO10 5DD, UK.
¹³ Schools of Chemical and Process Engineering, & Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK.

PMID: 35064954
DOI: 10.1002/adma.202106826

Abstract

The combination of strain and electrostatic engineering in epitaxial heterostructures of ferroelectric oxides offers many possibilities for inducing new phases, complex polar topologies, and enhanced electrical properties. However, the dominant effect of substrate clamping can also limit the electromechanical response and often leaves electrostatics to play a secondary role. Releasing the mechanical constraint imposed by the substrate can not only dramatically alter the balance between elastic and electrostatic forces, enabling them to compete on par with each other, but also activates new mechanical degrees of freedom, such as the macroscopic curvature of the heterostructure. In this work, an electrostatically driven transition from a predominantly out-of-plane polarized to an in-plane polarized state is observed when a PbTiO₃ /SrTiO₃ superlattice with a SrRuO₃ bottom electrode is released from its substrate. In turn, this polarization rotation modifies the lattice parameter mismatch between the superlattice and the thin SrRuO₃ layer, causing the heterostructure to curl up into microtubes. Through a combination of synchrotron-based scanning X-ray diffraction imaging, Raman scattering, piezoresponse force microscopy, and scanning transmission electron microscopy, the crystalline structure and domain patterns of the curved superlattices are investigated, revealing a strong anisotropy in the domain structure and a complex mechanism for strain accommodation.

Keywords: ferroelectric domains; free-standing membranes; microtubes; strain engineering.

Abstract

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