Impact of misfit dislocations on the polarization instability of epitaxial nanostructured ferroelectric perovskites

Abstract

Defects exist in almost all materials1 and defect engineering at the atomic level is part of modern semiconductor technology2,3. Defects and their long-range strain fields can have a negative impact on the host materials4,5. In materials with confined dimensions, the influence of defects can be even more pronounced due to the enhanced relative volume of the 'defective' regions. Here we report the dislocation-induced polarization instability of (001)-oriented Pb(Zr0.52Ti0.48)O3 (PZT) nanoislands, with an average height of 9 nm, grown on compressive perovskite substrates. Using quantitative high-resolution electron microscopy4, we visualize the strain fields of edge-type misfit dislocations, extending predominantly into a PZT region with a height of 4 nm and width of 8 nm. The lattice within this region deviates from the regular crystal structure. Piezoresponse force microscopy indicates that such PZT nanoislands do not show ferroelectricity. Our results suggest that misfit engineering is indispensable for obtaining nanostructured ferroelectrics with stable polarization.

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Figure 1: Cross-sectional and plan-view micrographs and calculated contrasts of the PZT nanoislands.
Figure 2: Geometric phase analysis of a misfit dislocation in a PZT nanoisland.
Figure 3: Quantitative measurements of long-range strain fields of the misfit dislocations along [100] and [001] axes using geometric phase analysis.
Figure 4: Local piezoelectric hysteresis loops measured by PFM.

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Acknowledgements

Part of this work was supported by Volkswagen Stiftung in the project 'Nano-sized Ferroelectric Hybrids' under the contract No. 5/77737, and part by DFG via FOR 404.

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Correspondence to Ming-Wen Chu.

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Chu, MW., Szafraniak, I., Scholz, R. et al. Impact of misfit dislocations on the polarization instability of epitaxial nanostructured ferroelectric perovskites. Nature Mater 3, 87–90 (2004). https://doi.org/10.1038/nmat1057

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