Reduced Variability in Threshold Switches Using Heterostructures of SiO x and Vertically Aligned MoS ₂

Two‐dimensional (2D) materials and their heterostructures offer promising pathways for intercalated ion migration and regulated filament growth in resistive switching (RS) devices, enabled by their van der Waals (vdW) gaps. In vertically aligned 2D materials, this vdW gap‐mediated ion transport holds great potential for high‐density integration and reliable RS performance for memristor crossbar arrays. However, the fundamental switching mechanisms and their contributions to the RS remain inadequately understood. In this work, we investigate silver (Ag) filament‐based threshold switching (TS) in heterostructures comprising vertically aligned 2D molybdenum disulfide (VAMoS 2 ) grown via sulfurization and silicon oxide (SiO x ). Compared to SiO x ‐only devices, the SiO x /VAMoS 2 devices exhibit TS with higher on‐threshold and hold voltages, each approximately 0.4 V, faster switching times down to 356 ns under a 4 V pulse, and a lower cycle‐to‐cycle on‐current variability of 3.0%. A physics‐based, variability‐aware model reveals that confined Ag ion migration within the vdW gaps in VAMoS 2 forms ultrathin seed filaments, which guide filament growth in the SiO x layer. These findings establish SiO x /VAMoS 2 heterostructures as a promising concept for reliable TS in vertical device architectures for emerging memories and neuromorphic computing.