Encapsulation and stability challenges in air-sensitive 2D ferroelectric materials

Two-dimensional (2D) ferroelectrics pair atomic-scale thickness with switchable polarization, but many promising chalcogenides and halides are severely air-sensitive. This review maps the mechanisms (displacive, interlayer sliding, electronic, dipolar, and topological) that govern in-plane and out-of-plane polarization, then examines how oxygen, moisture, and electrothermal stress drive oxidation, hydrolysis, blistering, and morphological failure that destabilize domains in the ultrathin limit. We compare synthesis and handling routes and also highlight encapsulation strategies and their impact on FeFETs, memristors, and vdW heterostructures. Our review shows the requirement for practical 2D ferroelectrics to develop standardized stability metrics, humidity/temperature-controlled testing, interfacial engineering, and scalable, atomically thin encapsulation compatible with wafer-level device integration. This review identifies environmental instability as the principal barrier to deploying 2D ferroelectrics and shows that atomically thin encapsulation and inert-atmosphere handling are essential rather than optional strategies for preserving polarization in the ultrathin limit.