Facile preparation KNN thin film with purity phase and excellent electrical properties

Abstract

Abstract Obtaining high purity alkali niobate (KxNa1-xNbO3) thin films without secondary phase on metal coated traditional silicon (Si) substrates via sol-gel technique has remained great challenges until now. Herein, we report (K0.5Na0.5NbO3; KNN) thin films successfully deposited on Pt/Ti/SiO2/Si(100) substrates by a simply effective sol-gel process. A comprehensive and systematic investigation of processing conditions on the microstructures and electrical properties of spin-coated KNN films were presented. We have found that phase purity and microstructures of KNN films are strongly influenced by content of alkali excess and the annealing temperature. Thin films with an equal excess amount of 10% mol K and Na (KNN1) sintered at 650 oC show high crystallinity with a preferred (100)-orientation degree of 78%, and homogeneous and dense surface with columnar structure and large grain size up to 254 nm. The result of quantitative XPS analysis has proved that the composition of the film is close to the chemical stoichiometry. As a consequence, the obtained films exhibit a large dielectric constant of 775 and low dielectric loss of 0.020 in the wide frequency range from 1 kHz up to 10 MHz. Furthermore, well ferroelectric behavior of KNN films showed remnant polarization, Pr of 10.73 µC/cm2, coercive field Ec of 74.48 kV/cm and lowest leakage current density of 9.23×10–10 A/cm2 at E ≈ 5 kV/cm.