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

Abstract

Van der Waals layered ferroelectrics, such as CuInP2S6 (CIPS), offer a versatile platform for miniaturization of ferroelectric device technology. Control of the targeted composition and kinetics of CIPS synthesis, enables the formation of stable self-assembled heterostructures of ferroelectric CIPS and non-ferroelectric In4/3P2S6 (IPS). Here, we use advanced quantitative scanning probe microscopy and density-functional-theory to explore in detail the nanoscale variability in dynamic functional properties of the CIPS-IPS heterostructure. We report evidence of fast ionic transport mediating an appreciable out-of-plane electromechanical response of CIPS in the paraelectric phase. Further, we map the local dielectric constant and ionic conductivity on the nanoscale as we thermally stimulate the ferroelectric-paraelectric phase transition, recovering the bulk dielectric peak of the transition at the nanoscale. Finally, we discover a conductivity enhancement at the CIPS/IPS interface, indicating the possibility of engineering its interfacial properties for next generation device applications.