Low-coercive-field ferroelectric hafnia with mobile domain walls

Abstract

The high coercive field ($\mathcal{E}_c$) of hafnia-based ferroelectrics presents a major obstacle to their applications. The ferroelectric switching mechanisms in hafnia that dictate $\mathcal{E}_c$, especially those related to nucleation-and-growth at the domain wall (DW), have remained elusive. Through deep-learning-assisted multiscale simulations, we determine the finite-temperature thermodynamics and switching mechanisms for diverse types of 180$^\circ$ DWs, revealing a complex, stress-sensitive mobility landscape. The propagation velocities for mobile DW types under various thermal conditions can be characterized with a single creep equation, featuring a creep exponent of 2. This unconventional critical exponent results from the nucleation of a half-unit-cell-thin, elliptically-shaped critical nucleus. Our multiscale approach not only reproduces the experimental thickness ($d$) scaling, $\mathcal{E}_c\propto d^{-\frac{2}{3}}$, but also predicts that $\mathcal{E}_c$ of HfO$_2$ can be engineered to $\approx$0.1 MV/cm, even lower than perovskite ferroelectrics. The theoretical lower bound of $\mathcal{E}_c$ afforded by ferroelectric hafnia offers opportunities to realize power-efficient, high-fidelity ferroelectric nanoelectronics.Comment: 19 pages, 4 figure