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Lead-free ferroelectric K 0:5 Na 0:5 NbO 3 (KNN) thin films have been synthesized by the chemical solution deposition. The optimization of excess amounts of K and Na in KNN precursor solutions was found to be effective for achieving perovskite KNN single-phase thin films with improved leakage current properties. It was revealed from Raman spectroscopic analysis data that a change in scattering mode was observed for the KNN thin films fabricated under various processing conditions. This change was due to the chemical composition fluctuation of K and Na in the KNN thin films after heat treatment. The leakage current and ferroelectric properties of the perovskite KNN thin films were strongly affected by the excess amounts of K and Na as well as the heating conditions of the precursor films. Optimized KNN thin films with 10 mol % excess K and Na exhibited a ferroelectric polarization-electric field (P-E) hysteresis loop with 2P r and 2E c values of 14 mC/cm 2 and 140 kV/ cm, respectively.

Lead-free piezoelectric K0.5Na0.5NbO3 thin films for microelectromechanical systems were fabricated via chemical solution process using metal alkoxide. Perovskite K0.5Na0.5NbO3 (KNN) single-phase thin films with good leakage current properties were successfully prepared by optimizing the KxNaxNbO3 (x≧0.5) composition of the precursor solution. The KNN thin films prepared from the solution with K0.55Na0.55NbO3 composition showed typical ferroelectric P–E hysteresis and field-induced strain loops. The 2Pr and 2Ec values of the K0.55Na0.55NbO3 films were 14 µC/cm2 and 140 kV/cm, respectively. From the slope of the field-induced butterfly loop, the effective d33 was found to be 46 pm/V.

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