Ba0.6Sr0.4TiO3 thick film derived by polymer modified MOSD route for tunable microstrip antenna applications

ABSTRACT Frequency and phase agile microstrip antenna applications require relatively thick Barium Strontium Titanate (BST) films for good tunability. In this work, Polymer (PEG-200) modified MOSD process route is developed to produce cracks free (Ba0.6, Sr0.4) TiO3 Thick film on Low loss ST-X quartz substrate. Structural and electrical characteristics of the deposited films were investigated using Atomic Force Microscope, X-Ray Diffraction, C-V and C-F characterizations. XRD characterization conformed the single BST phase with polycrystalline nature of the film. AFM analysis depicted equiaxed shaped grains with average grain size and roughness of 120 nm and 4.15 nm respectively. Dielectric tunability, dielectric constant and loss tangent of the deposited films were 36.46%, 310 and 0.0213 respectively at 1 MHz frequency using MIM capacitive structure where conductive oxide LNO was used as bottom electrode. The applicability of polymer modified BST thick films over low loss substrate as composite substrate for tunable microstrip antenna applications at microwave frequency was demonstrated by design, fabrication and testing of a compact frequency tunable microstrip antenna in coplanar configuration. The tunability exhibited at X band frequency proves the suitability of developed processed route for tunable antenna applications.