Structural and nanomechanical properties of sol–gel prepared (K, Na)NbO 3 thin films

Perovskite (K, Na)NbO 3 (KNN) thin films (~100 nm) were prepared by sol–gel/spin coating process on Pt/SiO 2 /Si substrates and annealed at 650 °C. The structural properties of KNN films were confirmed by X‐ray diffraction analysis (XRD), Raman spectroscopy and scanning electron, transmission electron and atomic force microscopy (SEM, TEM and AFM) analysis. Pure perovskite phase of K 0.65 Na 0.35 NbO 3 in nonstoichiometric composition with monoclinic symmetry in film was revealed. Uniform homogeneous microstructure of KNN film with the roughness (~6.9 nm) contained spherical particles (~50–90 nm). Nanoindentation technique was used to characterize the mechanical properties of KNN films. Elastic modulus and hardness of Pt, SiO 2 and KNN thin films were calculated from their composite values of KNN/Pt/SiO 2 /Si film/substrate system. The modulus and hardness of KNN film (71 and 4.5 GPa) were lower in comparison with SiO 2 (100 and 7.5 GPa). Pt film (~30 nm) did not influence the composite modulus, but had effect on hardness of KNN film. Copyright © 2015 John Wiley & Sons, Ltd.