Dresden 2020 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 11: Ferroics - Domains and Domain Walls (joint session KFM/MA)

KFM 11.5: Talk

Wednesday, March 18, 2020, 16:20–16:40, TOE 317

Robust In-Plane Ferroelectricity in Ultrathin Epitaxial Aurivillius Films — •Elzbieta Gradauskaite¹, Marco Campanini², Banani Biswas³, Christof W. Schneider³, Manfred Fiebig¹, Marta D. Rossell², and Morgan Trassin¹ — ¹Department of Materials, ETH Zurich, Switzerland — ²Electron Microscopy Center, Empa, Switzerland — ³LMX, Paul Scherrer Institut, Switzerland

Layered ferroelectrics exhibit functionalities beyond those of the classical ferroelectric perovskite compounds due to their highly anisotropic structure. Unfortunately, the layered architecture has been impeding their growth as single crystalline thin films, and thus their integration into oxide-electronic devices. We show that deposition of layered ferroelectric Bi5FeTi3O15 (BFTO) thin films on a lattice-matching NdGaO3 (001)-oriented orthorhombic substrate supports the epitaxial single-crystal form of this Aurivillius compound. Layer-by-layer growth is demonstrated, permitting in-situ control of thickness with sub-unit-cell accuracy and resulting in atomically flat surfaces. The achievement of twin-free films significantly enhances their uniaxial ferroelectric properties. In the ultrathin regime, such films exhibit in-plane polarization with a periodic arrangement of ferroelectric domains, which, in conjunction with uniaxial ferroelectric anisotropy, results in nominally charged domain walls. Hysteresis measurements reveal a remnant polarization of 16.5 µC cm^-2 with a remarkable endurance after 10¹⁰ switching cycles. The uniaxial in-plane ferroelectricity of Aurivillius thin films breaks new ground for alternative device paradigms less susceptible to the depolarizing-field effects.