General Synthesis Strategy of 2D Transition Metal Dichalcogenide Gradient Alloys for High‐Performance Optoelectronic Synapses

Abstract 2D transition metal dichalcogenide (TMD) gradient alloys hold great promise for electronic and optoelectronic applications, benefiting from their structural and compositional diversity as well as potential multifunctionalities. However, critical challenges remain in the controlled synthesis and unexplored uses of 2D TMD gradient alloys compared to single‐composition 2D TMDs. Herein, a “Face‐to‐Face” general synthesis strategy, which enables large‐area, uniform, and highly reproducible preparation of multiple types of 2D TMD gradient alloys in a single configuration through precise control on precursor supply, and the spatial confinement effect is reported. The synthesized single‐layer Mo 1‐x W x S 2 gradient alloy features a graded energy band and an alloyed region with moderate intrinsic sulfur vacancies, which is beneficial to achieving the high photo‐synaptic response. Optoelectronic synaptic devices utilizing the unique properties of 2D gradient alloys demonstrate various neuromorphic behaviors, such as outstanding‐index 161% paired‐pulse facilitation, stimuli‐dependent transition from short‐term plasticity to long‐term plasticity, emulation of the brain‐like learning processes, and simulation of neuromorphic vision on artificial neural network for handwritten digit recognition with over 95.6% accuracy. The present general synthesis method of 2D gradient alloys and their great potential as high‐performance optoelectronic synapses may open new frontiers for the 2D TMD family.