Dielectric and optical properties of Ba0.6Sr0.4Ti0.99Fe0.01O3 thin films deposited by pulsed laser deposition technique for microwave tunable devices

Ba0.6Sr0.4Ti0.99Fe0.01O3 films were deposited by Pulsed Laser Deposition (PLD) technique on two different substrates viz. Pt/Si and quartz, which were ex situ annealed at 700 °C in normal air atmosphere. The formation of single phase with perovskite structure and nanosize surface morphology of the films was ascertained by X-ray Diffraction studies and Atomic Force Microscopy (AFM) respectively. The detailed electrical properties like dielectric constant, loss tangent and tunability at low frequency were measured. The dielectric properties at microwave frequencies are also investigated in order to find suitability of the films for microwave tunable device applications. With the substitution of Fe3+ at B-site (1 mol%), the dielectric loss has been brought down due to better compensation of charges in the composition to 0.003 (measured at 11.06 GHz) in BST system. The optical properties of the film were also measured and the band gap of the films was calculated to ascertain the dielectric insulating properties. P-E hysteresis loop confirms its paraelectric behavior, which is one of the essential criterion for the films in tunable applications.