Domain Wall Evolution in Hf <sub>0.5</sub> Zr <sub>0.5</sub> O <sub>2</sub> Ferroelectrics under Field-Cycling Behavior
Sirui Zhang, Qinghua Zhang, Fanqi Meng, Ting Lin, Binjian Zeng, Lin Gu, Min Liao, Yichun Zhou
Abstract
HfO 2 -based ferroelectrics have evoked considerable interest owing to the complementary metal–oxide semiconductor compatibility and robust ferroelectricity down to a few unit cells. However, the unique wake-up effect of HfO 2 -based ferroelectric films severely restricts the improvement of their performance. In particular, the domain structure is an important characteristic of ferroelectric materials, which still has not been well understood in HfO 2 -based ferroelectrics. In this work, a Hf 0.5 Zr 0.5 O 2 ferroelectric thin film is grown on a typical Si substrate buffered with TiN electrode. The 90° domains of the Pca 2 1 ferroelectric phase with head-to-tail and tail-to-tail structures can be observed by C s-corrected scanning transmission electron microscope under their pristine condition. After waking up, the 180° domain is displayed in the ferroelectric phase. The remarkable differences in domain walls for 90° and 180° domains are characterized by qualitatively mapping the polarization distributions at the atomic scale. The domain wall changes from the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mo>[</mml:mo> <mml:mrow> <mml:mn>1</mml:mn> <mml:mn>0</mml:mn> <mml:mover accent="true"> <mml:mn>1</mml:mn> <mml:mo stretchy="true">¯</mml:mo> </mml:mover> </mml:mrow> <mml:mo>]</mml:mo> </mml:math> of the Hf 0.5 Zr 0.5 O 2 film to the [001] of the Hf 0.5 Zr 0.5 O 2 film. This result provides fundamental information for understanding the domain structure of HfO 2 -based ferroelectrics.