Post-synthesis tuning of dielectric constant via ferroelectric domain wall engineering

A promising mechanism for achieving colossal dielectric constants involves the use of insulating internal barrier layers, such as insulating domain walls in ferroelectrics. A key advantage of domain walls, compared to other stationary interfaces, is their mobility, offering the potential for post-synthesis adjustment of the dielectric constant. In this work, we demonstrate that altering the domain wall density enables the tuning of the dielectric constant in our template material, i.e., hexagonal ErMnO₃ single crystals. Through microscopy and macroscopic dielectric spectroscopy, we quantify changes in domain wall density and correlated these with changes in dielectric constant within a single sample. Analysis of the dielectric data suggests that the insulating domain walls act as “ideal” capacitors connected in series. Our approach to engineering the domain wall density can be readily extended to other control methods, e.g., electric fields or mechanical stresses, providing a degree of flexibility to in situ tune the dielectric constant.