Oxygen‐Self‐Supply Synthesis of Two‐Dimensional Fe ₂ Mo ₃ O ₈ Semiconductor Single Crystal With Colossal Ferroelectric Polarization

Developing ferroelectric semiconductors with colossal polarizations is crucial for fabricating large-capacity/high-density memory devices to meet the artificial intelligence demands. Although remarkable ferroelectric polarizations have been uncovered in perovskite-type oxides, the compatibility with electronic device scaling is becoming an insurmountable bottleneck. Here, we design an oxygen-self-supply chemical vapor deposition strategy to synthesize a 2D ferroelectric semiconductor single crystal of Fe₂Mo₃O₈. The unique FeO₄ tetrahedral cage contributes to the long displacement of the iron ion and induces the generation of large polarization. In parallel, the oxygen-deficient growth environment and ultrathin thickness enable the generation of oxygen vacancies and lattice distortion, which further enhance the ferroelectric polarization. As expected, ultrahigh polarization value up to 230 µC/cm² and ultralong endurance (4 × 10⁹ cycles) are achieved in 2D Fe₂Mo₃O₈, ten to one hundred times larger than most 2D ferroelectric materials. Concurrently, ferroelectric tunnel junctions based on 2D Fe₂Mo₃O₈ exhibit high switching speed and long retention time. This work represents a substantial leap for developing new 2D ferroelectric semiconductors with giant polarizations, which will stimulate the further exploration of large-capacity/high-density memory chips to overcome von Neumann architecture bottlenecks.