Anomalous polarization enhancement in a van der Waals ferroelectric material under pressure

Abstract

CuInP2S6 with robust room-temperature ferroelectricity has recently attracted much attention due to the spatial instability of its Cu cations and the van der Waals (vdW) layered structure. Herein, we report a significant enhancement of its remanent polarization by more than 50% from 4.06 to 6.36 µC cm−2 under a small pressure between 0.26 to 1.40 GPa. Comprehensive analysis suggests that even though the hydrostatic pressure suppresses the crystal distortion, it initially forces Cu cations to largely occupy the interlayer sites, causing the spontaneous polarization to increase. Under intermediate pressure, the condensation of Cu cations to the ground state and the polarization increase due cell volume reduction compensate each other, resulting in a constant polarization. Under high pressure, the migration of Cu cations to the center of the S octahedron dominates the polarization decrease. These findings improve our understanding of this fascinating vdW ferroelectric material, and suggest new ways to improve its properties.

Advances in the modulation engineering of ferroelectrics and multiferroics with non-chemical agents and factors: a review

“…Investigations have found that hydrostatic-pressure is a unique method for the enhancement of spontaneous polarization. As revealed by the experiment by Zhu et al , the 2D van der Waals ferroelectric CuInP 2 S 6 , 92 which was approximately 10 μm thick, was positioned on a plastic holder and electrically linked to a ferroelectric tester via copper wires (Fig. 7a).…”