Nonvolatile Memristor Based on WS2/WSe2 van der Waals Heterostructure with Tunable Interlayer Coupling

Abstract

Few-layered 2D materials are promising candidates to build highly integrated memristors. The interlayer coupling between two different 2D materials in heterostructure is crucial for their band structure modulation. In this study, an Au/WS₂/WSe₂/Au van der Waals heterostructure memristor is reported, the type-II band alignment heterostructure formed by few-layered WS₂ and WSe₂. The interlayer coupling of the heterostructure is tuned by annealing at different temperatures under argon atmosphere. The switching ratio and I–V cycle number of the memristor annealed at 350 °C is increased to 10⁵ and 300, which are 1000 times and 6 times that of unannealed memristor, respectively. The first-principle density functional theory (DFT) calculations indicate that the enhanced interlayer coupling caused by annealing significantly reduces the bandgap of heterojunction under applied voltage, thereby improving the electrical performance of the memristor. Additionally, the memristor exhibits notable synaptic plasticity, and simulations applied in the handwritten digit recognition classification achieve the highest accuracy of 92%. This work highlights a novel approach for improving the performance of memristors based on 2D heterostructure by tuning the interlayer coupling of the heterojunction.