First-principles study of charged steps on 180° domain walls in ferroelectric PbTiO3.

The atomic-scale mechanism of domain wall motion in ferroelectrics is commonly accepted to be nucleation and the movement of steps on the domain walls. Although very important in understanding the mechanism of domain wall motion and domain switching, the detailed atomic structures of steps have nevertheless been scarcely explored. In this work, the charged steps of these structures on 180° domain walls in PbTiO₃ were investigated using first-principles computations. Contrary to the previous understanding that there is a sudden jump at a step from one atomic plane to an adjacent plane, our computation results suggest that it is actually a gradual transition and the actual steps lie at atomic planes with the approximate Miller indices (3 0 ...). A large polarization rotation was found around the steps, making the polarization distribution Ising–Néel-like. The barriers for the motion of steps along domain walls were found to be much lower than those for which the domain wall is moving as a whole. These findings provide valuable information for further investigations of the domain switching mechanism at the atomic scale. [ABSTRACT FROM AUTHOR]