Tailoring Polarization Homogeneity in Discontinuous-Columnar Bi(Fe,Mn)O3 Thin Films through Strain Engineering via Controlled Dislocation Self-Assembly

Strain engineering in ferroelectric thin films is crucial for advancing next-generation electronic devices, yet conventional approaches relying on dislocation-density approaches often compromise structural integrity and electromechanical performance. Here, we develop a reduced-dislocation self-assembly strategy for Bi(Fe,Mn)O3 (BFMO) thin films that overcomes these constraints. By employing LaNiO3 (LNO) buffer layer, the interfacial lattice mismatch between BFMO and Ni-Cr substrate is reduced from ~3.8% to ~1.0%, suppressing dislocation density while promoting strain anisotropy. This guides discontinuous-columnar grains in BFMO, confining dislocations to self-assembly along grain boundaries in a topologically-protected configuration. The interaction creates periodic strain fluctuations and coordinated FeO6 octahedral tilting, significantly enhancing polarization homogeneity. This overcomes reliability challenges during aging, exhibiting ~10% higher remanent polarization, ~26% lower coercive field at RT, and ~62% better retention at industry-standard 60 °C after 60-day aging. These findings redefine defect engineering paradigms, showing how controlled dislocation rearrangement and strain-field mediation can unlock superior ferroelectric performance.