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

authors	Tkach, A; Santos, A; Zlotnik, S; Serrazina, R; Okhay, O; Bdikin, I; Costa, ME; Vilarinho, PM
nationality	International
journal	COATINGS
author keywords	KNN thin films; sol-gel; thermal expansion; stress/strain; ferroelectric hysteresis; dielectric properties
keywords	ELECTRICAL-PROPERTIES; THERMAL-EXPANSION; CERAMICS; SRTIO3
abstract	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.
publisher	MDPI
issn	2079-6412
year published	2018
volume	8
issue	12
digital object identifier (doi)	10.3390/coatings8120449
web of science category	Materials Science, Coatings & Films
subject category	Materials Science
unique article identifier	WOS:000455200300035