STM Observation of Atomistic Memory Effect in MoS2 Monolayers*

Field-driven non-volatile change in resistance, also known as memristor effect, has emerged as one of the most important phenomena in the development of components for high-density information storage and brain-inspired or neuromorphic computing. Recently, we discovered memristor effect in atomic monolayers of transitional metal dichalcogenide sandwich structures which has provided a new dimension of interest owing to the prospects of size scaling and the associated benefits. However, the origin of the switching mechanism in atomic sheets remains unclear. Here, using monolayer MoS₂ as a model material, atomistic imaging and spectroscopy reveal that metal substitution into sulfur vacancy results in a non-volatile resistance change. The experimental observations are supported by computational studies of defects and electronic states. These unexpected findings provide an atomistic understanding on the non-volatile switching mechanism and open new avenues for precision defect engineering, down to a singular defect, for realizing the smallest memristor for ultra-dense memory and computing.