Water-induced dual ultrahigh mobilities over 400 cm2 V−1 s−1 in 2D MoS2 transistors for ultralow-voltage operation and photoelectric synapse perception

Abstract

Two-dimensional (2D) MoS₂ is regarded as one of the most promising channel materials for field-effect transistors (FETs) due to its thickness-dependent bandgap and high air-stability. However, current MoS₂ FETs generally exhibit high power dissipation and low switching speed because of the general low field-effect mobility (μ ≈ 0.1–20 cm² V⁻¹ s⁻¹). Here, a facile and effective strategy to significantly enhance the μ over 400 cm² V⁻¹ s⁻¹ is proposed by capping the water molecules on the 2D MoS₂ surface of the FET. The device exhibits an ultralow operation voltage of 0.6 V as well as dual ultrahigh mobility behaviors from 409.1 cm² V⁻¹ s⁻¹ to 773.4 cm² V⁻¹ s⁻¹, which can be attributed to the ion-contributed quasi-electric-double-layer effect. More importantly, some intriguing synapse behaviors, such as excitatory/inhibitory postsynaptic current and controllable memory behavior, are successfully realized in our water-induced MoS₂ synapse transistors. This artificial synapse can also decode Morse-coded external electrical signals. Most importantly, the light-dependent accuracy of handwritten digit recognition can be found to be as high as 97.2% based on the proposed artificial visual recognition system. These results can open new avenues for the fascinating applications of high-performance photoelectric perception systems in future, such as autonomous vehicles, man–machine interfaces, etc.