Nonvolatile Ferroelectric-Domain-Wall Memory Embedded in a Complex Topological Domain Structure.

The discovery and precise manipulation of atomic-size conductive ferroelectric domain walls offers new opportunities for a wide range of prospective electronic devices, and the emerging field of walltronics. Herein, a highly stable and fatigue-resistant nonvolatile memory device is demonstrated, which is based on deterministic creation and erasure of conductive domain walls that are geometrically confined in a topological domain structure. By introducing a pair of delicately designed coaxial electrodes onto the epitaxial BiFeO3  film, a center-type quadrant topological domain with conductive charged domain walls can be easily created. More importantly, reversible switching of the quadrant domain between the convergent state with highly conductive confined walls and the divergent state with insulating confined walls can be realized, resulting in an apparent resistance change with a large on/off ratio of >104  and a technically preferred readout current (up to 40 nA). Owing to restrictions from the clamped quadrant ferroelastic domain, the device exhibits excellent restoration repeatability over 108  cycles and a long retention of over 12 days (>106  s). These results provide a new pathway toward high-performance ferroelectric-domain-wall memory, which may spur extensive interest in exploring the immense potential in the emerging field of walltronics.