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

We report on the microstructural and electrical properties of Mg-doped Ba0.6Sr0.4TiO3 thin films prepared by the metalorganic solution deposition technique using carboxylate-alkoxide precursors at a postdeposition annealing temperature of 750 degrees 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 Ba0.6Sr0.4TiO3 thin films at a frequency of 100 kHz were 450 and 0.013, respectively. The undoped Ba0.6Sr0.4TiO3 thin films exhibited a high tunability of 28.1% and resistivity of 0.4 x 10(12) Ohm cm at an applied electric field of 200 kV/cm. The Mg-doped Ba0.6Sr0.4TiO3 thin films exhibited significantly improved dielectric loss and insulating characteristics compared to undoped Ba0.6Sr0.4TiO3 thin films. The effects of Mg doping on the microstructural, dielectric, and insulating properties of Ba0.6Sr0.4TiO3 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 Ba0.6Sr0.4TiO3 thin films for integrated capacitor and microwave communication devices. (C) 2000 American Institute of Physics. [S0003-6951(00)02628-0].