Structural and nanomechanical properties of sol-gel prepared (K, Na)NbO3 thin films

Perovskite (K, Na)NbO3 (KNN) thin films (similar to 100nm) were prepared by sol-gel/spin coating process on Pt/SiO2/Si substrates and annealed at 650 degrees 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 K0.65Na0.35NbO3 in nonstoichiometric composition with monoclinic symmetry in film was revealed. Uniform homogeneous microstructure of KNN film with the roughness (similar to 6.9nm) contained spherical particles (similar to 50-90nm). Nanoindentation technique was used to characterize the mechanical properties of KNN films. Elastic modulus and hardness of Pt, SiO2 and KNN thin films were calculated from their composite values of KNN/Pt/SiO2/Si film/substrate system. The modulus and hardness of KNN film (71 and 4.5GPa) were lower in comparison with SiO2 (100 and 7.5GPa). Pt film (similar to 30nm) did not influence the composite modulus, but had effect on hardness of KNN film. Copyright (c) 2015 John Wiley & Sons, Ltd.