Influence of Aliovalent Doping on Dielectric Properties of Ba0.6Sr0.4TiO3 Thin Film for Voltage Tunable Applications

Ba0.6Sr0.4TiO3 thin film with aliovalent doping of acceptor nature at 'A' lattice sites of ABO(3) structure were prepared by a metal organic solution deposition (MOSD) technique on low loss quartz substrate. Oxide thin film having perovskite structure, namely, lanthanum nicklate (LaNiO3), also deposited using chemical solution deposition technique (CSD), was used as conductive bottom electrode. Solution properties and deposition process parameters were optimized for crack-free, uniform and smooth, pure and doped BST films on LNO electrode. The structural and microstructural analyses of the film were done using X-ray diffraction (XRD) and atomic force microscopy (AFM). Dielectric properties of the deposited film were studied using C-V and C-F electrical characterizations. The results indicate high tunability of 46%, very low loss tangent of 0.0065 with corresponding figure of merits of 71 for 2% K doped BST films at 1 MHz. The considerable improvement of dielectric properties of doped films compare to pure BST film is due to combined effect of perovskite lattice matched conductive bottom electrode and optimum doping level. These films had moderate dielectric constant, very low loss with good tunability which is suitable for tunable microwave applications.