Programmable Synapse-Like MoS₂ Field-Effect Transistors Phase-Engineered by Dynamic Lithium Ion Modulation

Synaptic transistors, inspired by brain plasticity, have shown strong potential as neuromorphic computing elements. Employing 2D materials for synaptic devices can provide an additional degree-of-freedom for monolithically integrated circuits owing to their atomically thin body and suitable electrical properties. Herein, a programmable molybdenum disulfide (MoS₂) field-effect transistor (FET) that emulates synaptic interaction via phase engineering, which is assisted by field-driven ionic modulation, is reported. Li⁺ ions selectively introduced into the van der Waals gap of the multilayer MoS₂ convert the 2H phase (semiconducting) into the 1T' phase (metallic), resulting in a seamless and reversible 1T'/2H heterophase homojunction device. The 1T'-MoS₂ region exhibits dynamic resistive switching behavior in a non-volatile fashion with a switching ratio of ≈10 owing to the Li⁺ ion redistribution under the applied electric field. By controlling the Schottky barrier height of the 1T'-MoS₂ channel, the behaviors of the monolithically integrated 1T'/2H-MoS₂ FET can be programmed with non-volatility. The 1T'/2H-MoS₂ heterophase homojunction device shows multilevel current output with a multistate computing window, indicating its potential as a stable multilevel neuro synaptic device. These results could enable the development of highly functional and energy-efficient neuromorphic systems via the monolithic integration of 2D materials.