Tailoring polarization homogeneity in discontinuous-columnar Bi(Fe,Mn)O₃ thin films via dislocation engineering with controlled self-assembly.

Abstract

Defect microstructures, particularly dislocations, are pivotal in determining the functional properties of ferroelectric thin films. While their density is routinely considered, the critical role of their spatial configuration has remained largely unexplored and difficult to control. Here, we develop a controlled self-assembly strategy for dislocations in Bi(Fe,Mn)O₃ thin films on Ni-Cr that directly addresses this challenge. By employing a LaNiO₃ buffer layer, we template a discontinuous-columnar grain structure and guide the self-assembly of edge dislocations along grain boundaries in a topologically-protected configuration. The resulting ordered microstructure promotes a more uniform strain field and more coherent FeO₆ octahedral tilting, significantly enhances polarization homogeneity, leading to a lower domain-switching barrier and a more uniform domain pinning effect. Consequently, the BFMO thin film exhibits dramatically superior aging stability after 60 days at 60 °C, exhibiting far smaller reductions in remanent polarization (~20%) and coercive field (~35%) compared to the BFMO thin film grown directly on Ni-Cr. These findings establish a defect engineering paradigm wherein the deliberate dislocation rearrangement is leveraged to unlock superior ferroelectric performance.