Transition from the m Phase to o Phase in an HZO Thin Film Revealed by In Situ TEM.
basic_science · Level V
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- Record sourced from PubMed, PMID 42406554.
- Also identified by DOI 10.1021/acs.nanolett.6c02399.
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Abstract
Understanding phase evolution in Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> (HZO) under electrical stress is essential for clarifying the mechanism of formation of the ferroelectric phase, which remains under debate because of the lack of direct observation. In this work, the electrically induced phase evolution of HZO, from the m phase to the ferroelectric o-<i>Pca</i>2<sub>1</sub> phase via an intermediate o-<i>Pbca</i> phase, was observed by using in situ transmission electron microscopy. Notably, this transition is accompanied by a change from a low-resistance state to a high-resistance state, which is attributed to oxygen vacancy redistribution under DC biasing. Meanwhile, Joule heating is believed to play an important role in the formation of the o-<i>Pbca</i> phase. Furthermore, density functional theory calculations confirmed that oxygen vacancies reduce the energy barriers for the m-to-o-<i>Pbca</i> transition and subsequent ferroelectric phase formation. These findings can deepen our understanding of phase evolution in hafnium-based oxides and provide a foundation for the structural design and reliability analysis of hafnium-based devices.