Two-dimensional (2D) materials have emerged as promising candidates for various optoelectronic applications based on their diverse electronic properties, ranging from insulating to superconducting. However, cooperative phenomena such as ferroelectricity in the 2D limit have not been well explored. Here, we report room-temperature ferroelectricity in 2D CuInP₂S₆ (CIPS) with a transition temperature of ∼320 K. Switchable polarization is observed in thin CIPS of ∼4 nm. To demonstrate the potential of this 2D ferroelectric material, we prepare a van der Waals (vdW) ferroelectric diode formed by CIPS/Si heterostructure, which shows good memory behaviour with on/off ratio of ∼100. The addition of ferroelectricity to the 2D family opens up possibilities for numerous novel applications, including sensors, actuators, non-volatile memory devices, and various vdW heterostructures based on 2D ferroelectricity.

Two‐dimensional (2D) materials have great potential in the fields of flexible electronics and photoelectronic devices due to their unique properties derived by special structures. The study of the mechanical properties of 2D materials plays an important role in next‐generation flexible mechanical electronic device applications. Unfortunately, traditional experiment models and measurement methods are not suitable for 2D materials due to their atomically ultrathin thickness, which limits both the theoretical research and practical value of the 2D materials. In this review, we briefly summarize the characterization of mechanical properties of 2D materials by in situ probe nanoindentation experiments, and discuss the effect of thickness, grain boundary, and interlayer interactions. We introduce the strain‐induced effect on electrical properties and optical properties of 2D materials. Then, we generalize the mechanical sensors based on various 2D materials and their future potential applications in flexible and wearable electronic devices. Finally, we discuss the state of the art for the mechanical properties of 2D materials and their opportunities and challenges in both basic research and practical applications. image