Comprehensive Study of Electrode Effect in Metal/CuInP₂S₆/Metal Heterostructures

The layered van der Waals CuInP2S6 (CIPS) features interesting functional behaviors, including reversible ferroelectric polarization, Cu ion migration, negative capacitance effect, etc. Here, the CIPS flakes were exfoliated from the CVT-grown high-quality single crystals, which were fabricated into metal/CIPS/metal heterostructures by conventional photolithography. It was found that the CIPS flakes persisted in the dominant out-of-plane polarization and the minor in-plane polarization. Clear hysteresis current–voltage (I–V) loops, as well as the rectifying character, were revealed in metal/CIPS/metal heterostructures, indicating the potential application as a memory device. Additionally, the different metal electrode could significantly modulate the Schottky-like barrier at metal/CIPS interfaces, resulting in symmetric or asymmetric I–V loops. The complicated I–V curves may have originated from the voltage-induced Cu ion migration, reversible ferroelectric polarization, and carrier (ion) trapping/detrapping. This work may facilitate the metal electrode selection for the ferroelectric CIPS-based device application.