Engineering ferroelectricity in monoclinic hafnia

Abstract

Ferroelectricity in the complementary metal-oxide semiconductor (CMOS)-compatible hafnia (HfO${}_2$) is crucial for the fabrication of high-integration nonvolatile memory devices. However, the capture of ferroelectricity in HfO${}_2$ requires the stabilization of thermodynamically-metastable orthorhombic or rhombohedral phases, which entails the introduction of defects (e.g., dopants and vacancies) and pays the price of crystal imperfections, causing unpleasant wake-up and fatigue effects. Here, we report a theoretical strategy on the realization of robust ferroelectricity in HfO${}_2$-based ferroelectrics by designing a series of epitaxial (HfO${}_2$)${}_1$/(CeO${}_2$)${}_1$ superlattices. The advantages of the designated ferroelectric superlattices are defects free, and most importantly, on the base of the thermodynamically stable monoclinic phase of HfO${}_2$. Consequently, this allows the creation of superior ferroelectric properties with an electric polarization $>$25 $\hat{I}¼$C/cm${}^2$ and an ultralow polarization-switching energy barrier at $\sim$2.5 meV/atom. Our work may open an entirely new route towards the fabrication of high-performance HfO${}_2$ based ferroelectric devices.