Ambient Moisture-Induced Self Alignment of Polarization in Ferroelectric Hafnia.

Abstract

The discovery of nanoscale ferroelectricity in hafnia (HfO₂) has paved the way for next generation high-density, non-volatile devices. Although the surface conditions of nanoscale HfO₂ present one of the fundamental mechanism origins, the impact of external environment on HfO₂ ferroelectricity remains unknown. In this study, the deleterious effect of ambient moisture is examined on the stability of ferroelectricity using Hf_0.5Zr_0.5O₂ (HZO) films as a model system. It is found that the development of an intrinsic electric field due to the adsorption of atmospheric water molecules onto the film's surface significantly impairs the properties of domain retention and polarization stability. Nonetheless, vacuum heating efficiently counteracts the adverse effects of water adsorption, which restores the symmetric electrical characteristics and polarization stability. This work furnishes a novel perspective on previous extensive studies, demonstrating significant impact of surface water on HfO₂-based ferroelectrics, and establishes the design paradigm for the future evolution of HfO₂-based multifunctional electronic devices.