Ion-migration memristive synaptic devices: mechanisms, device architectures, and integration strategies

Abstract Ion-migration memristive synaptic devices provide a physical route for hardware neuromorphic computing by using ionic redistribution, conductive-filament evolution, and interfacial barrier modulation to regulate synaptic weights. However, existing studies are often discussed according to specific material systems or individual device demonstrations, which makes it difficult to compare how different ion-migration mechanisms determine synaptic behavior, device stability, and integration potential. This mini review organizes recent progress from the perspective of operating mechanism and device type. Electrochemical metallization (ECM)-based synaptic devices are discussed with emphasis on metallic-filament formation and the challenge of achieving gradual and reproducible conductance modulation. Filamentary valence-change memory (VCM)-based devices are reviewed in terms of oxygen-vacancy channel evolution, while interfacial VCM devices are examined through interfacial ionic modulation and barrier-controlled analog switching. Hybrid ECM-VCM devices are further discussed as integrated designs that couple multiple ionic processes to balance switching window, stability, and multifunctionality. By linking mobile ionic species, switching pathways, and synaptic functions, this review provides a mechanism-based framework for understanding ion-migration memristive synaptic devices and for identifying the material, interface, and device-level issues that remain before scalable neuromorphic hardware can be realized.