Realizing Electronic Synapses by Defect Engineering in Polycrystalline Two-Dimensional MoS 2 for Neuromorphic Computing.

Neuromorphic computing based on two-dimensional transition-metal dichalcogenides (2D TMDs) has attracted significant attention recently due to their extraordinary properties generated by the atomic-thick layered structure. This study presents sulfur-defect-assisted MoS 2 artificial synaptic devices fabricated by a simple sputtering process, followed by a precise sulfur (S) vacancy-engineering process. While the as-sputtered MoS 2 film does not show synaptic behavior, the S vacancy-controlled MoS 2 film exhibits excellent synapse with remarkable nonvolatile memory characteristics such as a high switching ratio (∼10 3 ), a large memory window, and long retention time (∼10 4 s) in addition to synaptic functions such as paired-pulse facilitation (PPF) and long-term potentiation (LTP)/depression (LTD). The synaptic device working mechanism of Schottky barrier height modulation by redistributing S vacancies was systemically analyzed by electrical, physical, and microscopy characterizations. The presented MoS 2 synaptic device, based on the precise defect engineering of sputtered MoS 2 , is a facile, low-cost, complementary metal-oxide semiconductor (CMOS)-compatible, and scalable method and provides a procedural guideline for the design of practical 2D TMD-based neuromorphic computing.