Domain Wall Evolution in Hf0.5Zr0.5O2 Ferroelectrics under Field-Cycling Behavior

HfO2-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 HfO2-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 HfO2-based ferroelectrics. In this work, a Hf0.5Zr0.5O2 ferroelectric thin film is grown on a typical Si substrate buffered with TiN electrode. The 90 degrees domains of the Pca21 ferroelectric phase with head-to-tail and tail-to-tail structures can be observed by Cs-corrected scanning transmission electron microscope under their pristine condition. After waking up, the 180 degrees domain is displayed in the ferroelectric phase.The remarkable differences in domain walls for 90 degrees and 180 degrees domains are characterized by qualitatively mapping the polarization distributions at the atomic scale. The domain wall changes from the [101] of the Hf0.5Zr0.5O2 film to the [001] of the Hf0.5Zr0.5O2 film. This result provides fundamental information for understanding the domain structure of HfO2-based ferroelectrics.