Statistical Analysis of Uniform Switching Characteristics of Ta₂O₅-Based Memristors by Embedding In-Situ Grown 2D-MoS₂ Buffer Layers

A memristor based on emerging resistive random-access memory (RRAM) is a promising candidate for use as a next-generation neuromorphic computing device which overcomes the von Neumann bottleneck. Meanwhile, due to their unique properties, including atomically thin layers and surface smoothness, two-dimensional (2D) materials are being widely studied for implementation in the development of new information-processing electronic devices. However, inherent drawbacks concerning operational uniformities, such as device-to-device variability, device yield, and reliability, are huge challenges in the realization of concrete memristor hardware devices. In this study, we fabricated Ta₂O₅-based memristor devices, where a 2D-MoS₂ buffer layer was directly inserted between the Ta₂O₅ switching layer and the Ag metal electrode to improve uniform switching characteristics in terms of switching voltage, the distribution of resistance states, endurance, and retention. A 2D-MoS₂ layered buffer film with a 5 nm thickness was directly grown on the Ta₂O₅ switching layer by the atomic-pressure plasma-enhanced chemical vapor deposition (AP-PECVD) method, which is highly uniform and provided a superior yield of 2D-MoS₂ film. It was observed that the switching operation was dramatically stabilized via the introduction of the 2D-MoS₂ buffer layer compared to a pristine device without the buffer layer. It was assumed that the difference in mobility and reduction rates between Ta₂O₅ and MoS₂ caused the narrow localization of ion migration, inducing the formation of more stable conduction filament. In addition, an excellent yield of 98% was confirmed while showing cell-to-cell operation uniformity, and the extrinsic and intrinsic variabilities in operating the device were highly uniform. Thus, the introduction of a MoS₂ buffer layer could improve highly reliable memristor device switching operation.