3D Geometry and Functional Properties of Ferroelectric Domain Walls

Ferroelectric domain walls are quasi-2D interfaces that show great promise for nanoelectronic applications, including non-volatile memory, memristor technology and circuity components with ultra-small feature size. The functional properties of domain walls are mainly determined by their charge state, <i>i.e.,</i> the domain wall orientation relative to the spontaneous polarization. Being embedded in a 3D material, however, the domain walls are usually not strictly planar. In contrast, they can develop strongly corrugated 2D morphologies within the material that are inaccessible to standard microscopy techniques.<br/><br/>Using a combination of high-resolution FIB- and AFM-based tomographic methods and finite element modelling, we reveal the 3D domain wall structure in ErMnO₃ with nanoscale spatial resolution and correlate it with the emergent electronic transport properties. We show that the sub-surface domain wall curvature substantially contributes to the properties measured at the surface, which we demonstrate by simulating the spreading of injected currents within the measured domain wall network. Our findings confirm the importance of the 3D nanoscale structure of functional domain walls, establishing curvature as a new degree of freedom for controlling their electronic properties in future technological applications.