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


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 degrees C for 5 min. Despite an identical film morphology and thickness of similar to 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.



subject category

Materials Science


Tkach, A; Santos, A; Zlotnik, S; Serrazina, R; Okhay, O; Bdikin, I; Costa, ME; Vilarinho, PM

our authors


This work was funded by FEDER funds via Programa Operacional Factores de Competitividade-COMPETE and National funds via FCT (Fundacao para a Ciencia e a Tecnologia) within the Project CICECO-FCOMP-01-0124-FEDER-037271 (FCT PEst-C/CTM/LA0011/2013) as well as within FCT independent researcher grants (IF/00602/2013 and IF/00582/2015).

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