Effect of multi-domain structure on ionic transport, electrostatics, and current evolution in BaTiO₃ ferroelectric capacitor

The semiconducting properties of certain ferroelectric materials, partially caused by the interactions among ferroelectric polarizations, charged domain walls, and conducting point defects, pose a threat to the reliability of ferroelectrics used as dielectric material in capacitor devices, and is not yet fully understood. We proposed a physical model combining the phase-field method for ferroelectric domain structures and diffusion equations for defect transport to study the resistance degradation behavior in multi-domain tetragonal BaTiO₃ capacitors. We considered a hypothetical Ni/BaTiO₃/Ni single parallel plate capacitor configuration subject to 0.5 V dc bias at 25°C. It is found that 90° domain walls are charged, induce local space charge segregation, and form local electric potential barriers upon external bias that significantly influence the ionic transport behavior. Additionally, the 180° domain walls remain nearly charge neutral and have much less influence on ionic transport. The effect of domain wall and polarization orientations on the leakage current evolution is investigated. Our study could necessitate further understanding on the influence of ferroelectric state, ionic interactions, transport barriers, spatial distributions, and breakdown phenomena.