Interface-engineered ferroelectricity of epitaxial Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> thin films.
basic_science · Level V
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- Record sourced from PubMed, PMID 36997572.
- Also identified by DOI 10.1038/s41467-023-37560-3 and PMC identifier 10063548.
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Abstract
Ferroelectric hafnia-based thin films have attracted intense attention due to their compatibility with complementary metal-oxide-semiconductor technology. However, the ferroelectric orthorhombic phase is thermodynamically metastable. Various efforts have been made to stabilize the ferroelectric orthorhombic phase of hafnia-based films such as controlling the growth kinetics and mechanical confinement. Here, we demonstrate a key interface engineering strategy to stabilize and enhance the ferroelectric orthorhombic phase of the Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> thin film by deliberately controlling the termination of the bottom La<sub>0.67</sub>Sr<sub>0.33</sub>MnO<sub>3</sub> layer. We find that the Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> films on the MnO<sub>2</sub>-terminated La<sub>0.67</sub>Sr<sub>0.33</sub>MnO<sub>3</sub> have more ferroelectric orthorhombic phase than those on the LaSrO-terminated La<sub>0.67</sub>Sr<sub>0.33</sub>MnO<sub>3</sub>, while with no wake-up effect. Even though the Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> thickness is as thin as 1.5 nm, the clear ferroelectric orthorhombic (111) orientation is observed on the MnO<sub>2</sub> termination. Our transmission electron microscopy characterization and theoretical modelling reveal that reconstruction at the Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub>/ La<sub>0.67</sub>Sr<sub>0.33</sub>MnO<sub>3</sub> interface and hole doping of the Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> layer resulting from the MnO<sub>2</sub> interface termination are responsible for the stabilization of the metastable ferroelectric phase of Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub>. We anticipate that these results will inspire further studies of interface-engineered hafnia-based systems.