Anisotropic Growth of 2D Nonlayered α‐Fe ₂ O ₃ for Artificial Optoelectronic Synapse

Abstract Inspired by the human visual system, artificial optoelectronic synaptic devices are capable of performing perception, recognition, and memory tasks in a highly efficient and parallel way. Among the materials explored for constructing these devices, 2D transition metal oxides (TMOs) stand out due to their tunable compositions, exceptional stability, and unique optoelectronic properties. However, challenges such as complex device architectures, compromised material quality, and high energy consumption persist. Herein, the successful growth of 2D nonlayered α‐Fe ₂ O ₃ nanoflakes is reported via a molecular sieve‐assisted chemical vapor deposition (CVD) method. These nanoflakes, with a minimum thickness of two unit cells, exhibit high crystallinity, n‐type charge carrier transport properties, and response to 450 nm laser illumination. Notably, the charge trapping/de‐trapping at oxygen vacancies (V _O ) and the light‐induced ionization of V _O contribute to the distinct electron concentration and current hysteresis during cyclic voltage sweeps in the thin α‐Fe ₂ O ₃ nanoflakes. This mechanism results in a significantly prolonged photocurrent decay, enabling the emulation of biological synaptic behaviors such as excitatory postsynaptic current (EPSC), paired‐pulse facilitation (PPF), short‐term potentiation (STP), and long‐term potentiation (LTP). Combined with the scalability of the CVD process, this work highlights the potential of 2D α‐Fe ₂ O ₃ for applications in integrated artificial vision systems.