Precise structure and polarization determination of Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> with electron ptychography.
basic_science · Level V
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- Record sourced from PubMed, PMID 41690927.
- Also identified by DOI 10.1038/s41467-026-69514-w and PMC identifier 13018277.
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Abstract
Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> 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<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> 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<sup>2</sup>). 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<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub>, 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.