Stochastic behaviors of electrons through atom-vacancy defects in few atom-layer MoS2-FETs and neuromorphic device application

Atom-vacancy defects existing in various materials yield numerous physical phenomena, hindering high performance in electronic and photonic devices in some cases. These become more significant in two-dimensional (2D) (atomically) thin van der Waals (vdW) layers. Meanwhile, their applications to novel devices have gathered significant attention. Neuromorphic (NM) computation, which directly mimics the probabilistic operation of the human brain through ion transport, is such an effective example due to its potential in developing power- and size-efficient artificial intelligence applications. While magnetic tunnel junctions currently represent the mainstream approach in NM computation, they require local magnetic fields, posing integration challenges with CMOS circuits. Here, we demonstrate that sigmoid circuits—representative NM circuits—can be operated only by leveraging low-frequency noises [noise currents (IN) and power spectrum density (PSD)]—originating from the stochastic capture and emission of electrons through atom-vacancy defects—in few-atom-layer semiconductor molybdenum disulfide field-effect transistors. Modulating the back-gate voltage allows control of the magnitude of electrical hysteresis loops in the current and IN (PSDs), thereby enabling and regulating the stochastic electron behaviors and emergence of the observed sigmoid operation. This work paves the way for the development of NM circuits through defect engineering in vdW 2D semiconductors, eliminating the need for magnetic fields.