Effect of potassium-doped concentration on structures and dielectric performance of barium-strontium-titanate films

•K-doping is shown to enhance crystallization and refines grains.•K-doping can decrease surface non-perovskite structures.•K-doping improves dielectric properties especially enhances tunabilities.•5% doping gives the best structure and combination of dielectric properties.

Potassium-doped barium strontium titanate films were prepared, and the effect of K-doped concentration on the structures and dielectric properties has been studied. XRD patterns exhibit that all films mainly grow along (110) orientation and reveal a cubic ABO3 perovskite structure. K+ ions first enter A sites then B sites, but the lattice parameters are a little larger than that of the pure film. The doped films show average grain sizes of 18–27 ± 3 nm. K-doping enhances crystallization, and 5% mol ratio corresponds to a moderate crystallization. XPS reveals that non-perovskite structures on doped film surfaces are less than that on the pure film surface, first decrease then increase with increasing concentration, and are associated with adsorbed carbon contaminants. The dielectric properties are significantly improved with high tunable capabilities. 5% doping corresponds to the best combination of dielectric properties, which is consistent with the structures.