Enhancing ferroelectric stability: wide-range of adaptive control in epitaxial HfO<sub>2</sub>/ZrO<sub>2</sub> superlattices.

Li, Jingxuan; Deng, Shiqing; Ma, Liyang; Si, Yangyang; Zhou, Chao; Wang, Kefan; Huang, Sizhe; Yang, Jiyuan et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

The metastability of the polar phase in HfO<sub>2</sub>, despite its excellent compatibility with the complementary metal-oxide-semiconductor process, remains a key obstacle for its industrial applications. Traditional stabilization approaches, such as doping, often induce crystal defects and impose constraints on the thickness of ferroelectric HfO<sub>2</sub> thin films. These limitations render the ferroelectric properties vulnerable to degradation, particularly due to phase transitions under operational conditions. Here, we demonstrate robust ferroelectricity in high-quality epitaxial (HfO<sub>2</sub>)<sub>n</sub>/(ZrO<sub>2</sub>)<sub>n</sub> superlattices, which exhibit significantly enhanced ferroelectric stability across an extended thickness range. Optimized-period superlattices maintain stable ferroelectricity from up to 100 nm, excellent fatigue resistance exceeding 10<sup>9</sup> switching cycles, and a low coercive field of ~0.85 MV/cm. First-principles calculations reveal that the kinetic energy barrier of phase transition and interfacial formation energy are crucial factors in suppressing the formation of non-polar phases. This work establishes a versatile platform for exploring high-performance fluorite-structured superlattices and advances the integration of HfO<sub>2</sub>-based ferroelectrics into a broader range of applications.