Origin of the Critical Thickness in Improper Ferroelectric Thin Films
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Date
2023-04-12
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Journal Article
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Abstract
Improper ferroelectrics are expected to be more robust than conventional ferroelectrics against depolarizing field effects and to exhibit a much-desired absence of critical thickness. Recent studies, however, revealed the loss of ferroelectric response in epitaxial improper ferroelectric thin films. Here, we investigate improper ferroelectric hexagonal YMnO3 thin films and find that the polarization suppression, and hence functionality, in the thinner films is due to oxygen off-stoichiometry. We demonstrate that oxygen vacancies form on the film surfaces to provide the necessary charge to screen the large internal electric field resulting from the positively charged YMnO3 surface layers. Additionally, we show that by modifying the oxygen concentration of the films, the phase transition temperatures can be substantially tuned. We anticipate that our findings are also valid for other ferroelectric oxide films and emphasize the importance of controlling the oxygen content and cation oxidation states in ferroelectrics for their successful integration in nanoscale applications.
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published
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Journal / series
Volume
15 (14)
Pages / Article No.
18482 - 18492
Publisher
American Chemical Society
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Subject
YMnO3; Improper ferroelectricity; Critical thickness; Interfaces; Oxygen vacancies; Transmission electron microscopy; Electron energy loss spectroscopy
Organisational unit
03918 - Fiebig, Manfred / Fiebig, Manfred
03903 - Spaldin, Nicola A. / Spaldin, Nicola A.
Notes
Funding
188414 - Multifunctional oxide electronics using natural ferroelectric superlattices (SNF)
810451 - Hidden, entangled and resonating orders/HERO (EC)
810451 - Hidden, entangled and resonating orders/HERO (EC)
Related publications and datasets
Is previous version of: 10.1021/acsami.3c00412