Raman Spectra Study of K_0.5Na_0.5NbO₃ Ferroelectric Thin Films

Abstract

We have fabricated K 0.5 Na 0.5 NbO 3 (KNN) thin films on Pt substrates by a chemical solution deposition method and investigated the effect of K and Na excess (0–30 mol %) for KNN thin film. The KNN film with 20 mol % excess K and Na was an optimized KNN perovskite phase. From the Raman spectra, a change in the scattering mode was observed due to the chemical composition fluctuations of the excess K and Na. The peak of the ( v 1 + v 5 ) internal vibrational mode in the NbO 6 octahedra was split into two vibration modes which were shifted toward lower or higher wavenumbers depending on the K and Na cation deficiencies or redundancies.