Scaling Effects on Ferroelectric Polarization Switching and Activation Electric Field in Epitaxial Hf _0.5 Zr _0.5 O ₂ Nanodots

Abstract Hafnium oxide (HfO 2 )‐based ferroelectric thin films, particularly Hf 0.5 Zr 0.5 O 2 (HZO), have emerged as promising candidates for next‐generation nonvolatile memory due to their stable ferroelectricity at sub‐10 nm thicknesses. While HZO thin films have been widely studied, nanoscale ferroelectric architectures such as nanodots remain largely unexplored, especially in the context of polarization switching and domain wall dynamics. Here, the switching behavior and domain wall migration kinetics in epitaxial HZO nanodots with diameters of 30, 40, and 50 nm and thicknesses of 7, 10, and 13 nm are systematically investigated, using time‐resolved piezoresponse force microscopy. The domain wall velocity is found to increase with nanodot diameter but decrease with thickness, ranging from 1.2 to 2.1 m s −1 . A maximum velocity of 2.3 m s −1 is observed in a 10 nm thick HZO thin film. The piezoelectric response also improves with increasing aspect ratio, consistent with enhanced depolarization fields. Activation electric fields, determined via Merz's law, increase with decreasing nanodot thickness and diameter, reaching 6.65 MV cm −1 in the thinnest configuration. These behaviors are attributed to electrostatic boundary effects and depolarization charges surrounding the switching region. These results provide critical insights into ferroelectric scaling limits and offer design guidelines for high‐density, energy‐efficient ferroelectric memory and logic devices.