Hf 0.5 Zr 0.5 O 2 emerges as a promising candidate for next-generation ferroelectric memories and transistors. However, the intrinsic nature of its ferroelectricity remains a subject of debate, primarily stemming from challenges in the precise characterization of nanoscale polycrystallinity and multiphase coexistence. Here, we investigate substrate-free Hf 0.5 Zr 0.5 O 2 films using multislice electron ptychography, achieving a resolution of 25 picometers with capabilities for oxygen imaging, depth resolution, and vacancy quantification. Precise measurements reveal that the polarization displacement in ferroelectric phase is ∼ 56 ± 6 picometers (corresponding to a polarization ∼ 34 ± 4 μC/cm 2 ). We further identify significant polarization suppression near grain boundaries, while there is negligible change in the 180° neutral domain walls. Furthermore, we demonstrate the existence of the 180° head-to-head charged domain wall in Hf 0.5 Zr 0.5 O 2 , which is confined within a single unit cell layer. At such a charged domain wall, the atomic displacement is reduced to ∼ 4 picometers, with oxygen vacancies accumulating up to 20%. Notably, the polar layers neighboring the 180º head-to-head charged domain wall remain unchanged. The precise determination of these structural features with ultra-high spatial resolution offers critical information for optimizing and designing new hafnium-based ferroelectric devices.
Gao et al. (Sat,) studied this question.