Ferroelectricity mediated by ferroelastic domain switching in HfO2-based epitaxial thin films

Herein, ferroelastic domain switching from the nonpolar b-axis to the polar c-axis oriented domain in 7%-YO1.5-substituted HfO2 (YHO-7) epitaxial ferroelectric films is demonstrated. Scanning transmission electron microscopy (STEM) indicates that the polarization of a pristine film deposited on a Sn...

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Veröffentlicht in:Applied physics letters 2018-11, Vol.113 (21)
Hauptverfasser: Shimizu, Takao, Mimura, Takanori, Kiguchi, Takanori, Shiraishi, Takahisa, Konno, Toyohiko, Katsuya, Yoshio, Sakata, Osami, Funakubo, Hiroshi
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Sprache:eng
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Zusammenfassung:Herein, ferroelastic domain switching from the nonpolar b-axis to the polar c-axis oriented domain in 7%-YO1.5-substituted HfO2 (YHO-7) epitaxial ferroelectric films is demonstrated. Scanning transmission electron microscopy (STEM) indicates that the polarization of a pristine film deposited on a Sn-doped In2O3/(001)YSZ substrate by the pulsed laser deposition method tends to be along the in-plane direction to avoid a strong depolarization field with respect to the out-of-plane direction. Applying an electric field aids in ferroelastic domain switching in YHO-7 films. Such films exhibit ferroelectric characteristics with a relatively large saturated polarization around 30 μC/cm2 by polarization reorientation from the in-plane to the out-of-plane directions and an increased dielectric constant. The synchrotron X-ray diffraction measurements with a focused beam for the pristine and poled area indicate ferroelastic 90° domain switching as the odd number reflection disappears, which is only allowed in the nonpolar b-axis orientation. STEM observations also show a significant increase in the c-axis oriented domain. This observation of ferroelastic domain switching strongly supports the conclusion that the ferroelectricity of HfO2 originates from the non-centrosymmetric orthorhombic phase.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.5055258