Structural, optical and electrical characteristics BaSrTiOx thin films: Effect of deposition pressure and annealing

Among perovskite oxide materials, BaSrTiOx (BST) has attracted great attention due to its potential applications in oxide-based electronics. However, reliability and efficiency of BST thin films strongly depend on the precise knowledge of the film microstructure, as well as optical and electrical properties. In the present work, BST films were deposited at room temperature using radio frequency magnetron sputtering technique. The impact of deposition pressure, partial oxygen flow, and post-deposition annealing treatment on film microstructure, surface morphology, refractive index, and dielectric constants were studied by X-ray diffraction, scanning electron microscopy, spectrophotometry, ellipsometry, photoluminescence, as well as capacitance-voltage measurements. Well-adhered and uniform amorphous films were obtained at room temperature. For all as-deposited films, the average optical transmission was ~ 85% in the VIS-NIR spectrum. The refractive indices of BST films were in the range of 1.90-2.07 (λ = 550 nm). Post-deposition annealing at 800 °C for 1 h resulted in polycrystalline thin films with increased refractive indices and dielectric constants, however reduced optical transmission values. Frequency dependent dielectric constants were found to be in the range of 46-72. However, the observed leakage current was relatively small, about 1 μA. The highest FOM values were obtained for films deposited at 0.67 Pa pressures, while charge storage capacity values increased with increased deposition pressure. Results show that room-temperature grown BST films have potential for device applications.