Mg-doped Ba0.6Sr0.4TiO3 thin films for tunable microwave applications

We report on the microstructural and electrical properties of Mg-doped ${\mathrm{Ba}}_{\mathrm{0.6}}{\mathrm{Sr}}_{\mathrm{0.4}}{\mathrm{TiO}}_3$ thin films prepared by the metalorganic solution deposition technique using carboxylate-alkoxide precursors at a postdeposition annealing temperature of 750 °C. The structure and morphology of the films were analyzed by x-ray diffraction and atomic force microscopy studies. The electrical measurements were conducted on metal-ferroelectric-metal capacitors using Pt as the top and bottom electrode. The typical measured small signal dielectric constant and dissipation factor of undoped ${\mathrm{Ba}}_{\mathrm{0.6}}{\mathrm{Sr}}_{\mathrm{0.4}}{\mathrm{TiO}}_3$ thin films at a frequency of 100 kHz were 450 and 0.013, respectively. The undoped ${\mathrm{Ba}}_{\mathrm{0.6}}{\mathrm{Sr}}_{\mathrm{0.4}}{\mathrm{TiO}}_3$ thin films exhibited a high tunability of 28.1% and resistivity of ${\text{0.4×10}}^{12}$ Ω cm at an applied electric field of 200 kV/cm. The Mg-doped ${\mathrm{Ba}}_{\mathrm{0.6}}{\mathrm{Sr}}_{\mathrm{0.4}}{\mathrm{TiO}}_3$ thin films exhibited significantly improved dielectric loss and insulating characteristics compared to undoped ${\mathrm{Ba}}_{\mathrm{0.6}}{\mathrm{Sr}}_{\mathrm{0.4}}{\mathrm{TiO}}_3$ thin films. The effects of Mg doping on the microstructural, dielectric, and insulating properties of ${\mathrm{Ba}}_{\mathrm{0.6}}{\mathrm{Sr}}_{\mathrm{0.4}}{\mathrm{TiO}}_3$ thin films were analyzed. The high dielectric constant, low dielectric loss, high tunability, and low leakage current show the potential of pure and Mg-doped ${\mathrm{Ba}}_{\mathrm{0.6}}{\mathrm{Sr}}_{\mathrm{0.4}}{\mathrm{TiO}}_3$ thin films for integrated capacitor and microwave communication devices.