A stable monoclinic variant and resultant robust ferroelectricity in single-crystalline hafnia-based films.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41044443.
- Also identified by DOI 10.1038/s41467-025-63907-z and PMC identifier 12494953.
- Licence recorded as CC BY-NC-ND.
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Abstract
The ferroelectricity in nanoscale HfO<sub>2</sub>-based films enables their applications more promising than that of the perovskite oxides, taking into account the easy compatibility with the modern silicon-based semiconductor technology. However, the well-known polar orthorhombic phase is thermodynamically metastable, making the applications of HfO<sub>2</sub>-based ferroelectrics challenging in terms of uncontrollability and consequently instability of the physical performance in electronic devices. Here we report the robust ferroelectricity in stable monoclinic Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> single-crystalline films, which was known as non-polar before. The as-prepared films display high endurance performance of wake-up free and non-fatigue behavior up to 10<sup>12</sup> cycles. Multimode imaging under aberration-corrected scanning transmission electron microscopy reveals that such an unexpected ferroelectric behavior is resultant from an antiphase boundaries-derived monoclinic polar variant (space group, Pc) intergrown with the nonpolar monoclinic phase (P2<sub>1</sub>/c). The switching barrier for the stable polar variant is only 20~50% of that for the metastable orthorhombic phase according to the calculation by the nudged elastic band method. These findings provide a practical approach for designing robust ferroelectricity in hafnia-based materials and would be helpful for the development of lower energy-cost and long-life memory devices compatible with integrated circuit technology.