Revealing Fast Cu-Ion Transport and Enhanced Conductivity at the CuInP2S6-In4/3P2S6 Heterointerface

Van der Waals layered ferroelectrics, such as CuInP2S6 (CIPS), offer a versatile platform for miniaturization of ferroelectric device technologies. Control of the targeted composition and kinetics of CIPS synthesis enables the formation of stable self-assembled heterostructures of ferroelectric CIPS and nonferroelectric In4/3P2S6 (IPS). Here, we use quantitative scanning probe microscopy methods combined with density functional theory (DFT) to explore in detail the nanoscale variability in dynamic functional properties of the CIPS-IPS heterostructure. We report evidence of fast ionic transport which mediates an appreciable out-of-plane electromechanical response of the CIPS surface in the paraelectric phase. Further, we map the nanoscale dielectric and ionic conductivity properties as we thermally stimulate the ferroelectric-paraelectric phase transition, recovering the local dielectric behavior during this phase transition. Finally, aided by DFT, we reveal a substantial and tunable conductivity enhancement at the CIPS/IPS interface, indicating the possibility of engineering its interfacial properties for next generation device applications.

Automated summary

This study uses quantitative scanning probe microscopy methods combined with density functional theory to explore the nanoscale variability in the dynamic functional properties of the ferroelectric material CIPS and the nonferroelectric material IPS. It reveals evidence of fast ionic transport that mediates a significant out-of-plane electromechanical response of the CIPS surface in the paraelectric phase. It also recovers the local dielectric behavior during the ferroelectric-paraelectric phase transition and demonstrates the tunable conductivity enhancement at the CIPS/IPS interface.