Atomic-resolution Imaging of Functional Electronic Inversion Layers at Ferroelectric Domain Walls

Ferroelectric domain walls hold great promise as functional two-dimensional materials because of their unusual electronic properties. Particularly intriguing are the so-called charged walls where a polarity mismatch causes local, diverging electrostatic potentials requiring charge compensation and hence a change in the electronic structure. These walls can exhibit significantly enhanced conductivity and serve as a circuit path. Here we use atomic-resolution STEM-EELS to directly probe the charge transfer at these charged ferroelectric domain walls in ErMnO3. Our direct quantification of the charge transfer to the domain boundary gives insight into the the formation—and eventual activation—of an inversion layer that acts as the channel for the charge transport. The findings provide new insight into the domain-wall physics in ferroelectrics and foreshadow the possibility to design elementary digital devices for all-domain-wall circuitry.