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Strain-Mediated Substrate Effect on the Dielectric and Ferroelectric Response of Potassium Sodium Niobate Thin Films

1
Department of Materials and Ceramics Engineering, CICECO–Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal
2
Institute of Electronic Materials Technology (ITME), Wolczynska 133, 01-919 Warsaw, Poland
3
Nanotechnology Research Division, Centre for Mechanical Technology and Automation (TEMA), Department of Mechanical Engineering, University of Aveiro, 3810-193 Aveiro, Portugal
*
Author to whom correspondence should be addressed.
Coatings 2018, 8(12), 449; https://doi.org/10.3390/coatings8120449
Received: 28 September 2018 / Revised: 22 November 2018 / Accepted: 3 December 2018 / Published: 6 December 2018
(This article belongs to the Special Issue Piezoresistive and Piezoelectric Thin Films for Sensors)
If piezoelectric thin films sensors based on K0.5Na0.5NbO3 (KNN) are to achieve commercialization, it is critical to optimize the film performance using low-cost scalable processing and substrates. Here, sol–gel derived KNN thin films are deposited using a solution with 5% of potassium excess on Pt/TiO2/SiO2/Si and Pt/SrTiO3 substrates, and rapid thermal annealed at 750 °C for 5 min. Despite an identical film morphology and thickness of ~335 nm, an in-plane stress/strain state is found to be tensile for KNN films on Pt/TiO2/SiO2/Si, and compressive for those on Pt/SrTiO3 substrates, being related to thermal expansion mismatch between the substrate and the film. Correspondingly, KNN films under in-plane compressive stress possess superior dielectric permittivity and polarization in the parallel-plate-capacitor geometry. View Full-Text
Keywords: KNN thin films; sol–gel; thermal expansion; stress/strain; ferroelectric hysteresis; dielectric properties KNN thin films; sol–gel; thermal expansion; stress/strain; ferroelectric hysteresis; dielectric properties
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MDPI and ACS Style

Tkach, A.; Santos, A.; Zlotnik, S.; Serrazina, R.; Okhay, O.; Bdikin, I.; Costa, M.E.; Vilarinho, P.M. Strain-Mediated Substrate Effect on the Dielectric and Ferroelectric Response of Potassium Sodium Niobate Thin Films. Coatings 2018, 8, 449.

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