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

Alexander Tkach, André Santos, Sebastian Zlotnik, Ricardo Serrazina, Olena Okhay, Igor Bdikin, Maria Elisabete Costa, Paula M. Vilarinho
2018 Coatings  
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
more » ... sile 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.
doi:10.3390/coatings8120449 fatcat:gidmd7wsmbdelaq5jhpshrmdjm