Optical properties of lead- free ferroelectric potassium sodium niobate (KxNa1-xNbO3) thin films

Potassium Sodium Niobate (KxNa1-xNbO3 or KNN) is the most attractive lead- free ferroelectric material used in sensor and transducer applications due to its promising piezoelectric properties and high electromechanical coupling coefficient. Besides that, KNN also has good non-linear optical properties and high transparency in the visible range. In the present work, high quality KxNa1-xNbO3 (x=0.35; KNN) thin film has been synthesized on quartz substrate by means of pulsed laser deposition (PLD) process under optimized processing conditions and later post- annealed for better crystallinity. X-Ray Diffraction (XRD) pattern and Raman scattering spectroscopy confirm the highly crystalline nature of KNN thin film. The optical properties of annealed KNN thin film are interrogated from the UV- Visible transmittance spectra. The band-gap of the KNN thin film in optical region is calculated to be equal to 3.75 eV.