Emerging van der Waals ferroelectrics: Unique properties and novel devices

Abstract

The past few decades have witnessed extensive and intensive studies on ferroelectric materials with switchable electric polarization due to their broad device applications. Emerging van der Waals (vdW) layered ferroelectrics ingeniously assemble strong covalent-bonded polar or non-polar monolayers through weak vdW forces. These atom arrangements contrast with the stacking of conventional oxide ferroelectrics, enabling unprecedented ferroelectric physics in terms of polarization origin, polar stabilization, and switching kinetics. Combined with other inherent optical and electrical features, the vdW ferroelectrics can undoubtedly provide a new, versatile platform for advancing fundamental physics and revolutionizing device technology. In this review, we summarize the unique ferroelectric properties in experimentally confirmed vdW ferroelectrics, particularly those properties that expand our understanding of ferroelectric switching. We also elucidate how some of these properties can intrinsically reduce depolarized instability at the atomic limit. Finally, we discuss innovative devices enabled by distinct properties of vdW ferroelectrics for electronic, optoelectronic, and energy-harvesting applications, and highlight possible future research lines.