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

ABSTRACT 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 Fe 2 Mo 3 O 8 . The unique FeO 4 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/cm 2 and ultralong endurance (4 × 10 9 cycles) are achieved in 2D Fe 2 Mo 3 O 8 , ten to one hundred times larger than most 2D ferroelectric materials. Concurrently, ferroelectric tunnel junctions based on 2D Fe 2 Mo 3 O 8 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.