Spontaneous pattern of orthogonal ferroelectric domains in epitaxial KNN films.
In: Journal of Applied Physics, Jg. 134 (2023-11-28), Heft 20, S. 1-12
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Zugriff:
Lead-free piezoelectric (K, Na)NbO 3 (KNN) is considered one of the promising candidates for the replacement of Pb(Zr x Ti 1−x )O 3 . Several studies underlined the issue of K and Na volatility with increasing deposition temperatures, leading to high leakage currents in thin films, which still represents a major drawback for applications. This paper shows how epitaxial growth with concomitant preferred orientation of KNN films on niobium-doped strontium titanate (Nb:STO) depends on growth temperature and substrate strain. A preferred out-of-plane polar (001) orientation of KNN is obtained at high temperatures (>600 °C), while (100) orientation is dominant for lower ones. The (001) orientation is forced out-of-plane due to the sizeable in-plane stress derived from a negative lattice mismatch of pseudo-cubic KNN with respect to the underlying cubic (001) Nb:STO substrate. Moreover, we show that K-Na deficiency and high leakage of epitaxial KNN films deposited at high temperatures are accompanied by the appearance of a pattern of orthogonal spontaneous ferroelectric domains aligned to the [100] and [010] directions of Nb:STO. This pattern, visible in secondary electron microscopy, piezoforce response microscopy, and conductive atomic force microscopy images, is uncorrelated to the surface morphology. Supported by reciprocal space mapping by x-ray diffraction, this phenomenon is interpreted as the result of strain relaxation via ferroelectric domain formation related to K-Na deficient films displaying a sizable and increasing compressive strain when grown on Nb:SrTiO 3 . Our findings suggest that strain engineering strategies in thin films could be used to stabilize specific configurations of piezo- and ferroelectric domains. [ABSTRACT FROM AUTHOR]
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Titel: |
Spontaneous pattern of orthogonal ferroelectric domains in epitaxial KNN films.
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Autor/in / Beteiligte Person: | Groppi, C. ; Maspero, F. ; Asa, M. ; Pavese, G. ; Rinaldi, C. ; Albisetti, E. ; Badillo-Avila, M. ; Bertacco, R. |
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Zeitschrift: | Journal of Applied Physics, Jg. 134 (2023-11-28), Heft 20, S. 1-12 |
Veröffentlichung: | 2023 |
Medientyp: | academicJournal |
ISSN: | 0021-8979 (print) |
DOI: | 10.1063/5.0171349 |
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