Copper Ion Migration in van der Waals CuInP2S6 Devices with Vertical and Lateral Structures

Van der Waals CuInP2S6(CIPS) exhibits interesting functional behaviors, including reversible ferroelectric polarization, copper ion (Cu+) migration and negative capacitance effect. Besides, CIPS are found to persist in both major out-of-plane polarization and minor in-plane polarization. In this work, we fabricate two-terminal CIPS devices based on Au/CIPS/Au heterostructure with vertical and lateral conduction channels respectively. The vertical device exhibits bipolar switching characteristic, while lateral one shows only unipolar switching along with rectification. Moreover, the current is significantly higher in vertical case than that in lateral case, which is explained by carrier transport and Cu+ migration along short and long channels. These experimental results provide physical insight into CIPS conductions as a promising candidate for future information storage devices.