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

• Published in: ACS nano 2022-09, Vol.16 (9), p.15347-15357
• Main Authors: Checa, Marti, Jin, Xin, Millan-Solsona, Ruben, Neumayer, Sabine M., Susner, Michael A., McGuire, Michael A., O’Hara, Andrew, Gomila, Gabriel, Maksymovych, Petro, Pantelides, Sokrates T., Collins, Liam
• Format: Article
• Language: English
• Subjects: copper indium thiophosphate; ferroelectrics; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; ionic conductor; phase transition; piezoresponse force microscopy; scanning dielectric microscopy
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/acsnano.2c06992

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.