Nearly Barrierless\nPolarization Switching Mechanisms\nin ZrO<sub>2</sub> Having Perpendicular In-Plane Domain Walls

The polarization switching mechanism in ferroelectric\nZrO<sub>2</sub> involves the nucleation and subsequent migration of\nnonpolar domain\nboundaries; however, the fundamental mechanism driving this process\nremains inadequately understood. The present study introduces a mechanism\nfor nearly barrierless polarization switching in 180° domain\nwalls, facilitated by a the half-unit-cell nonpolar phase between\noppositely polarized domains. Based on density functional theory (DFT)\ncalculations, two types of 180° domain walls are explored, featuring\nhead-to-head and tail-to-tail polarization boundaries, with nonpolar\northorhombic <i>Pbcm</i> and tetragonal <i>P</i>4<sub>2</sub>/<i>nmc</i> phases as the respective domain\nwalls. The calculations reveal exceptionally low energy barriers of\n17.5 and 10.1 meV for migrating these <i>Pbcm</i> and <i>P</i>4<sub>2</sub>/<i>nmc</i> boundaries by half a\nunit cell through the domains. An evaluation of the impact of defects\non domain wall motion is achieved by introducing 2% oxygen vacancies\nor 3% Si doping, which induces a significant increase in the barrier\nmotion activation energy, suggesting that defects serve as barriers\nto polarization switching.