Structure and piezo-ferroelectricity relationship study of (K0.5Na0.5)0.985La0.005NbO3 epitaxial films deposited on SrTiO3 by sputtering

• Published in: Scientific reports Vol. 7; no. 1; pp. 1 - 12
• Main Authors: H´Mŏk, H´Linh, Martínez-Aguilar, E., Gervacio-Arciniega, J. J., Vendrell, X., Siqueiros-Beltrones, J. M., Raymond-Herrera, O.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 18-12-2017; Nature Publishing Group
• Subjects: 639/301/1005/1007; 639/766/1130/2798; Heat treatment; Heat treatments; Humanities and Social Sciences; Microscopy; Microstructure; multidisciplinary; Physical properties; Polarization; Science; Science (multidisciplinary); Thin films; Transmission electron microscopy; X-ray diffraction
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-017-17767-3

This work demonstrates that the rf-sputtering technique, combined with appropriate heat treatments, is potentially effective to develop new materials and devices based on oxide-interface and strain engineering. We report a study of the structural-physical properties relationship of high crystalline quality, highly oriented and epitaxial thin films of the lead-free (K
0.5
Na
0.5
)
0.985
La
0.005
NbO
3
(KNNLa) compound which were successfully deposited on Nb-doped SrTiO
3
substrates, with orientations [100] (NSTO100) and [110] (NSTO110). The crystalline growth and the local ferroelectric and piezoelectric properties were evaluated by piezoresponse force microscopy combined with transmission electron microscopy and texture analysis by X-ray diffraction. Conditioned by the STO surface parameters, in the KNNLa films on NSTO100 coexist a commensurate [001]-tetragonal phase and two incommensurate [010]-monoclinic phases; while on NSTO110 the KNNLa films grew only in an incommensurate [101]-monoclinic phase. Both samples show excellent
out-of-plane
polarization switching patterns consistent with 180° domains walls; while for KNNLa/NSTO100 ferroelectric domains grow with the polarization pointing
down
, for KNNLa/NSTO110 they prefer to grow with the polarization pointing
up
. Comparing with previous reports on epitaxial KNN films, we find our samples to be of very high quality regarding their crystalline growth with highly ordered ferroelectric domains arrangements and, consequently, great potential for domain engineering.