Depletion Layers and Domain Walls in Semiconducting Ferroelectric Thin Films

Commonly used ferroelectric perovskites are also wide-band-gap semiconductors. In such materials, the polarization and the space-charge distribution are intimately coupled, and this Letter studies them simultaneously with no a priori ansatz on either. In particular, we study the structure of domain walls and the depletion layers that form at the metal-ferroelectric interfaces. We find the coupling between polarization and space charges leads to the formation of charge double layers at the 90\ifmmode^\circ\else\textdegree\fi{} domain walls, which, like the depletion layers, are also decorated by defects like oxygen vacancies. In contrast, the 180\ifmmode^\circ\else\textdegree\fi{} domain walls do not interact with the defects or space charges. Implications of these results to domain switching and fatigue in ferroelectric devices are discussed.