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arXiv · 2204.05252

Finite-size effects on the ferroelectricity in rhombohedral HfO$_2$

Francesco Delodovici·Paolo Barone·Silvia Picozzi
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Abstract

In this work we analyze the finite-size effects on the structural properties and on the polarization of the rhombohedral phase of HfO$_2$ subjected to a biaxial compressive strain. We show how the presence of surface charges affects the polarization, leading to a strong reduction with respect to its bulk value. This reduction can be ascribed to two mechanisms: the coupling between compressive strain and the phase-transition order parameter; the changes in the ferroelectric distortion. We give two alternative explanations of this phenomenon: from an atomistic point of view, analyzing the evolution of the bond lengths, and from a symmetry-analysis point of view, considering the changes in the amplitude of the symmetry-allowed distortions, when a slab configuration is considered. These results are independent on the slab-thickness in the considered range, suggesting the absence of a critical thickness for ferroelectricity in HfO$_2$, in agreement with the proposed improper nature of hafnia ferroelectricity.

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Francesco Delodovici, Paolo Barone, Silvia Picozzi. 2022-04-11. Finite-size effects on the ferroelectricity in rhombohedral HfO$_2$. https://doi.org/10.1103/physrevb.106.115438

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