Boosting Inversion Symmetry Breaking in Epitaxial Tetragonal ZrO<sub>2</sub> Via Atomic Layer Deposition.
basic_science · Level V
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- Record sourced from PubMed, PMID 40679869.
- Also identified by DOI 10.1021/acs.nanolett.5c02741 and PMC identifier 12314912.
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Abstract
The stabilization of intermediate polar phases in fluorite-structured oxides is critical for advancing ferroelectric and antiferroelectric applications. Here, we report the stabilization of epitaxial polar tetragonal (T) ZrO<sub>2</sub>. Epitaxial Hf<sub><i>x</i></sub>Zr<sub>1-<i>x</i></sub>O<sub>2</sub> thin films (x = 1, 0.75, 0.5, 0.25, and 0) are synthesized on (001) yttria-stabilized zirconia substrates via atomic layer deposition. The emergence of the unprecedented polar T-ZrO<sub>2</sub> phase deviates from the expected phase transition from nonpolar HfO<sub>2</sub> through ferroelectric Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> to antiferroelectric Zr-rich Hf<sub><i>x</i></sub>Zr<sub>1-<i>x</i></sub>O<sub>2</sub>. Second harmonic generation measurements reveal unexpected inversion symmetry breaking in T-phase ZrO<sub>2</sub>. High-resolution 4D-scanning transmission electron microscopy further confirms the presence of electric dipoles originating from off-centered oxygen displacements. These findings establish a pathway for the low-temperature epitaxial synthesis of HfO<sub>2</sub>-ZrO<sub>2</sub>-based materials and provide critical insight into the polar nature of T-phase ZrO<sub>2</sub>.