Threading dislocations in epitaxial ferroelectric PbZr_0.2Ti_0.8O₃ films and their effect on polarization backswitching

Abstract

The existence of threading dislocations in ferroelectric heterostructures has been frequently reported. However, their origin and impact on the ferroelectric properties are not sufficiently understood. PbZr_0.2Ti_0.8O₃/SrRuO₃ heterostructures were epitaxially grown by pulsed-laser deposition (PLD) onto vicinal SrTiO₃(001) substrates. The threading dislocations exhibited by the PbZr_0.2Ti_0.8O₃ films were investigated by cross-sectional and plan-view (high-resolution) transmission electron microscopy. Many threading dislocations were dissociated into dipoles spanning a, most probably lead-rich, stacking fault. It is likely that these dislocations are able to pin 180° ferroelectric domains, as suggested by a comparison between piezo-force microscope and transmission electron micrographs obtained on identical samples. Local backswitching of the polarization was observed in the vicinity of such threading dislocations.

Acknowledgements

The work has been partly funded by Volkswagen Foundation, through the “Nanosized ferroelectric hybrids” project no I/80897 and partly by DFG through FOR 404. Sincere thanks are due to S. Swatek and N. Schammelt (MPI, Halle) for the TEM sample preparation and assistance in PLD-system maintenance, respectively.