Atomic level study of charge-compensations at ferroelectric interfaces

Understanding the charge-compensation mechanism at oxide hetero-interfaces is important for fundamental science and also for practical applications. Here, using high resolution STEM, we found that the depolarization field induced by polarization discontinuity at (110) BiFeO₃/GdScO₃(010)_O (where the subscript “O” denotes orthorhombic indices) heteor-interfaces are compensated by different mechanisms evolving with film thickness. Thin films with thickness <30nm were screened by 180° and 109° ferroelectric stripe domains, where the vortex arrays at the end of the 109° domain walls were also found. Interestingly, thicker films with ~70nm thicknesses were compensated by an interfacial layer exhibiting exact in-plane polarizations with several nanometers thicknesses, which has not been observed before. Our results are important for understanding the interfacial charge compensations of ferroelectric films and thus designing novel ferroelectric based electric devices.