Insulating domain walls for colossal dielectric constants

Ferroelectric domain walls are receiving increasing attention as naturally occurring 2D interfaces with distinct properties relative to the surrounding material^1,2. While most of this attention focuses on domain walls with relatively enhanced conductivity, very recent work now also considers the potential of insulating domain wall that form a network of insulating interfaces within improper ferroelectrics³. The focus here is on emulating the dielectrics’ communities` use of internal barrier layers to achieve “colossal” dielectric constants (ε’ > 1000) for capacitor applications, but utilizing insulating domain walls as the barrier layers. As this research concept is still in its infancy, to date, colossal values of dielectric constants have not been achieved via direct control of insulating domain walls.

In this talk, we show how colossal dielectric constants can be achieved via control of domain wall density in our prototypical improper ferroelectrics system, hexagonal-ErMnO₃. We use macroscopic measurements of the dielectric constant, before and after changing the domain wall density - via controlled cooling rates across the Kibble-Zurik-like transition - to show an order-of-magnitude change in dielectric constant. This order-of-magnitude changes in dielectric constant correlate excellently with the order-of-magnitude change in domain wall density, directly imaged with piezoelectric force microscopy and scanning electron microscopy. This shows the potential for using insulating domain walls for colossal dielectric constant in this template materials system and highlights the opportunities of insulating domain walls in other improper ferroelectric systems.

(1) Nataf, G. F. et al. Nat. Rev. Phys. 2020. https://doi.org/10.1038/s42254-020-0235-z.

(2) Evans, D. M. et al. Phys. Sci. Rev. 2020, 5 (9), 20190067. https://doi.org/10.1515/psr-2019-0067.

(3) Puntigam, L. et al. J. Appl. Phys. 2021, 129 (7), 74101. https://doi.org/10.1063/5.0038300.