In situ observation of oxygen ion dynamics in topological phase change memristors through self-assembled interface design.

Resistive switching memory represents a potentially transformative advancement in next-generation nonvolatile memory and neuromorphic technologies. Recently, vertically aligned nanocomposites (VANs) have been proposed to optimize the memristive performance of single-phase memories. However, the microscopic mechanism of dynamic resistive switching in these VAN architectures is still elusive. Here, we built up a VAN structure with brownmillerite SrCoO (BM-SCO) and magnesium oxide (MgO), where the topological phase transformation in BM-SCO provides a well-defined facile vertical path for oxygen ion migration within the vertical interfaces between BM-SCO and MgO phases. Compared with the BM-SCO memristor, the (BM-SCO):(MgO) VAN memristor exhibits advantages in resistive switching and simulates various synaptic functions, achieving high accuracy in image recognition tasks. Using in situ scanning transmission electron microscopy, we revealed the microscopic mechanism of oxygen ion migration dynamics along the vertical interfaces. Our work substantially advances the understanding of resistive switching mechanism and further demonstrates the great potential of VAN architectures for practical application in high-performance resistive memory.