A grease for domain walls motion in HfO2-based ferroelectrics

A large coercive field E (C) of HfO2 based ferroelectric devices poses critical performance issues in their applications as ferroelectric memories and ferroelectric field effect transistors. A new design to reduce E (C) by fabricating nanolaminate Hf0.5Zr0.5O2/ZrO2 (HZZ) thin films is used, followed by an ensuing annealing process at a comparatively high temperature 700 degrees C. High-resolution electron microscopy imaging detects tetragonal-like domain walls between orthorhombic polar regions. These walls decrease the potential barrier of polarization reversal in HfO2 based films compared to the conventional domain walls with a single non-polar spacer, causing about a 40% decrease in E (C). Capacitance versus electric field measurements on HZZ thin film uncovered a substantial increase of dielectric permittivity near the E (C) compared to the conventional Hf0.5Zr0.5O2 thin film, justifying the higher mobility of domain walls in the developed HZZ film. The tetragonal-like regions served as grease easing the movement of the domain wall and reducing E (C).