Ferroelectric HfO$_2$-ZrO$_2$ multilayers with reduced wake-up

TL;DR

This study demonstrates ferroelectricity in a thick, multilayer HfO₂-ZrO₂ film, showing stabilized polar phases and improved wake-up behavior, advancing the potential for high-performance ferroelectric devices.

Contribution

It introduces the first demonstration of ferroelectricity in a 50 nm thick multilayer HfO₂-ZrO₂ film, highlighting enhanced wake-up behavior due to multilayer interfaces.

Findings

Achieved ferroelectricity in the thickest multilayer film to date.

Multilayer structure stabilizes polar phase in ZrO₂ layers.

Higher breakdown strength accelerates wake-up behavior.

Abstract

Since the discovery of ferroelectricity in HfO$_2$ thin films, significant research has focused on Zr-doped HfO$_2$ and solid solution (Hf,Zr)O$_2$ thin films. Functional properties can be further tuned via multilayering, however, this approach has not yet been fully explored in HfO$_2$-ZrO$_2$ films. This work demonstrates ferroelectricity in a 50 nm thick, solution-processed HfO$_2$-ZrO$_2$ multilayer film, marking it as the thickest multilayer film to date exhibiting ferroelectric properties. The multilayer structure was confirmed through transmission electron microscopy (TEM) and energy dispersive x-ray spectroscopy, with high-resolution TEM revealing grain continuity across multiple layers. This finding indicates that a polar phase in the originally paraelectric ZrO$_2$ layer, can be stabilized by the HfO$_2$ layer. The film attains a remanent polarization of 9 uC/cm$^2$ and exhibits accelerated wake-up behavior, attributed to its higher breakdown strength resulting from the incorporation of multiple interfaces. These results offer a faster wake-up mechanism for thick ferroelectric hafnia films.