Ionic Pathways to Neuromorphic Function: Direct Visualization of Oxygen Migration in Interface Synaptic Memristive...

Neuromorphic computing mimics the adaptive and energy efficient information processing of biological synapses, yet the atomic-scale ionic mechanisms underlying synaptic behavior remain largely unexplored. In oxide-based resistive switching devices, oxygen migration dictates conductance modulation, but direct, cycle-resolved visualization of these dynamics has been limited. Here, we demonstrate that co-doping and engineered oxide-metal interfaces in HfO2 based devices enable p-n-like memristors with reversible interfacial ionic motion, leading to robust, high-performance neuromorphic operation compared to undoped HfO2. Our results establish that co-doping not only stabilizes oxygen vacancies but also facilitates interfacial oxygen migration, enabling tunable, multilevel conductance states and reliable synaptic plasticity in oxide-based memristors, which these dynamics directly visualized via in-operando optical spectroscopies. By correlating electrical performance with Raman, photoluminescence, and dark-field signatures, this work provides the first direct, cycle-resolved evidence linking interface and defect engineering to controllable ionic motion and emergent neuromorphic functionality, highlighting a general strategy for designing high-endurance, optically trackable memristive devices.