Synergistic Regulation of Filament Dynamics in Ag/SiOx/TiOy Memristors by Bilayer Thickness Matching and Compliance Current

Ag-based electrochemical metallization (ECM) memristors offer low operating voltages and high ON/OFF ratios, but stochastic filament formation and rupture lead to severe switching variability. To address this, Ag/SiOx/TiOy/p++-Si memristors were systematically studied by separately varying the TiOy thickness, SiOx thickness, and compliance current (Icc). Moderate TiOy thickness and SiOx thickness yielded improved voltage uniformity and a larger switching window, whereas excessive SiOx thinning degraded the ON/OFF ratio. Moderate Icc was consistent with more complete filament dissolution and stable switching, while excessive Icc was consistent with filament overgrowth and residual channels after RESET, leading to a compressed resistance window. Conduction and XPS analyses suggest trap-related transport in the HRS and quasi-Ohmic conduction in the LRS, consistent with defect-assisted Ag+ migration mediated by oxygen vacancies and low-valence cations. Based on these results, a SiOx/TiOy bilayer thickness synergistic matching model is proposed: SiOx is proposed to mainly regulate Ag+ supply/injection, while TiOy is proposed to provide a defect-rich environment for Ag+ migration and nucleation and to determine the migration distance. Icc acts as an external control that governs the extent of filament growth without introducing an additional switching mechanism. The optimized device exhibited stable bipolar switching, preliminary endurance, retention, and preliminary device-to-device consistency under the optimized condition. This work provides a practical strategy for regulating filament dynamics through thickness-engineered bilayer design in Ag-based ECM memristors.