Subunit cell-level measurement of polarization in an individual polar vortex.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31700996.
- Also identified by DOI 10.1126/sciadv.aav4355 and PMC identifier 6824850.
- Licence recorded as CC BY-NC.
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Abstract
Recently, several captivating topological structures of electric dipole moments (e.g., vortex, flux closure) have been reported in ferroelectrics with reduced size/dimensions. However, accurate polarization distribution of these topological ferroelectric structures has never been experimentally obtained. We precisely measure the polarization distribution of an individual ferroelectric vortex in PbTiO<sub>3</sub>/SrTiO<sub>3</sub> superlattices at the subunit cell level by using the atomically resolved integrated differential phase contrast imaging in an aberration-corrected scanning transmission electron microscope. We find, in vortices, that out-of-plane polarization is larger than in-plane polarization, and that downward polarization is larger than upward polarization. The polarization magnitude is closely related to tetragonality. Moreover, the contribution of the Pb─O bond to total polarization is highly inhomogeneous in vortices. Our precise measurement at the subunit cell scale provides a sound foundation for mechanistic understanding of the structure and properties of a ferroelectric vortex and lattice-charge coupling phenomena in these topological ferroelectric structures.