Improvement of dielectric tunability and loss tangent of (Ba,Sr)TiO3 thin films with K doping

Ba0.6Sr0.4TiO3 thin films doped with K were deposited on Pt/Ti/SiO2/Si substrates by the chemical solution deposition method. The structure, surface morphology and the dielectric and tunable properties of Ba0.6Sr0.4TiO3 thin films have been studied in detail. The K content in Ba0.6Sr0.4TiO3 thin films has a strong influence on the material's properties including surface morphology and the dielectric and tunable properties. It was found that the Curie temperature of K-doped Ba0.6Sr0.4TiO3 films shifts to a higher value compared with that of undoped Ba0.6Sr0.4TiO3 thin films, which leads to a dielectric enhancement of K-doped Ba0.6Sr0.4TiO3 films at room temperature. At the optimized content of 0.02 mol, the dielectric loss tangent is reduced significantly from 0.057 to 0.020. Meanwhile, the tunability is enhanced obviously from 26% to 48% at the measured frequency of 1 MHz and the maximum value of the figure of merit is 23.8. This suggests that such films have potential applications for tunable devices