Unconventional Thermal Stability of Domain Framework in Ferroelectric CuInP₂S₆

Achieving stable and persistent polarization characteristics in ferroelectric (FE) materials is crucial for fabricating high-density, low-power multifunctional memories. In this study, we conducted a comprehensive investigation of the 2D FE material CuInP₂S₆ (CIPS), employing piezoelectric force microscopy (PFM), scanning transmission electron microscopy (STEM), and Raman spectroscopy. By comparing CIPS with and without the nonferroelectric (NFE) phase, we observed unexpected stability of the domain framework at high temperatures. This was evidenced by in situ temperature-dependent PFM measurements and Raman spectra. STEM analysis revealed Cu ion defects and charge accumulation at the FE/NFE interface, which contributed to the thermal stability due to a strong pinning effect. This work highlights the significant positive impact of NFE phases on the thermal stability of FE CIPS, providing insights into the development of controllable FE polarization switching and the potential application of highly reliable and durable multifunctional devices.