Electric properties of barium–strontium titanate thin films deposited by two-step radio-frequency sputtering

Barium-strontium titanate (BST) thin films were prepared by a two-step deposition using radio-frequency magnetron sputtering on Pt/Ti/SiO2-buffered Si(100) substrate. The initial BST layer thickness and intermediate annealing strongly affect the resultant electric properties of the two-step BST thin films. The optimal two-step BST films, with a first-layer thickness of 30 nm intermediate annealed at 610 °C under 1 torr oxygen. The dielectric breakdown and leakage current density of the two-step film are above 625 kV/cm and 9.5 nA/cm2 at 100 kV/cm, respectively, compared with 400 kV/cm and 17 nA/cm2 for the one-step films. We conclude that the two-step deposition dramatically improves dielectric breakdown and enhances leakage current density while keeping the dielectric constant uninfluenced.