Structural and mechanical properties of La 1/3 NbO 3 and La 1/3 TaO 3 thin films prepared by chemical solution deposition

In this work, properties of perovskite lanthanum niobate La1/3NbO3 (LN) and tantalate La1/3TaO3 (LT) transparent thin films (∼200 nm thickness) prepared by chemical solution deposition on Pt/SiO2/Si substrates were described. The precursors and films were analyzed using FTIR and XPS spectra, XRD and SEM imaging. The both films after annealing at 1100 °C contained perovskite phase with a small fraction of pyrochlore LaNb5O14 (in LN). The heterogeneous microstructure of LN film was composed from spherical or needle-like particles and homogeneous LT film that resulted in significant changes of their mechanical properties. The elastic modulus and hardness of these films were characterized for the first time by conventional and continuous stiffness (CSM) nanoindentation. The LT film modulus (E) and hardness (H) were higher (∼105.7 and 5.3 GPa) than LN (∼91.5 and 3.8 GPa). The effect of microstructure on mechanical properties is significant. In addition, the average Derjaguin–Muller–Toporov (DMT)-based elastic modulus of LN film surface were estimated ∼50 GPa using AFM PeakForce QNM elastic mapping. The findings presented here can contribute to the fabrication of LN and LT films for the application to electrolytic thin film devices.