Intrinsic 90° charged domain wall and its effects on ferroelectric properties

The domain is an important characteristic of ferroelectric materials, and the type of domain can have significant effects on the performance of ferroelectric materials. In particular, the unique wake-up and fatigue effects of Hf0.5Zr0.5O2 (HZO) films severely restrict improvements in terms of film performance. Recently, using integrated differential phase contrast (iDPC) scanning transmission electron microscopy (STEM) imaging, we observed the existence of intrinsic tail-to-tail 90 degrees domain structures, charged do-main walls (CDWs), and polarization relaxation on the TiN/HZO/TiN interfaces of HZO films. Based on this experimental investigation, we establish a phase-field model of the tail-to-tail 90 degrees CDWs based on the time-dependent Ginzburg-Landau equation. In our model, the tail-to-tail 90 degrees CDW affects the mesoscopic domain switching through a built-in electric field, which, in turn, affects the macroscopic ferroelectric properties of the thin film. The following conclusions are drawn: (a) the CDWs that are distributed hori-zontally or vertically along the thickness of the film cause a A-wake-up effect (antiferroelectric-like wake-up) with double hysteresis loops or a S-wake-up effect (spindle-like wake-up), with thick portions in the middle and both ends points of the hysteresis loop; (b) the S-wake-up caused by the CDWs distributed along the thickness of the film performs badly in fatigue tests and is easier to break down. The model proposed herein reveals the mechanism of the wake-up effect in hafnium oxide-based ferroelectric films. It provides a theoretical basis for the development of a new type of hafnium oxide-based ferroelectric memory system. (C) 2022 Acta Materialia Inc. Published by Elsevier Ltd.

Automated summary

This study reveals the effects of tail-to-tail 90 degrees domain structures and charged domain walls (CDWs) on the performance of Hf0.5Zr0.5O2 (HZO) films through experimental observation and the establishment of a phase-field model. It provides a theoretical basis for the development of a new type of hafnium oxide-based ferroelectric memory system.