Microwave Properties of Ferroelectric (BaxSr1-x)TiO3 Thin Films for Microwave Tunable Devices
Dr. Won-Jeong Kim
Microwave tunable devices have been extensively studied due to increased demands for high quality wireless communications and radar applications. Electric field dependent dielectric constant of ferroelectrics allow us to develop electrically tunable microwave devices, which have advantages over other tunable technologies.
Ferroelectric (BaxSr1-x)TiO3 (BST) has been investigated to develop a new class of electrically tunable microwave devices, such as tunable oscillators, tunable filters, delay lines and phase shifters. Thin BST films were deposited onto (001) MgO single crystals by pulsed laser deposition. The output of a short pulse excimer laser with = 248 nm was focused onto a stoichiometric BST target with energy density of ~ 2 J/cm2. Electrodes of the devices have been fabricated by a standard MMIC procedure. Microwave properties of the BST films were measured using a HP 8510C network analyzer at frequency range of 0.045-20 GHz from coplanar type phase shifters. Dielectric constant of ferroelectric BST films were extracted using a modified conformal-mapping partial-capacitance method from measured scattering S-parameters. In this presentation, ferroelectric film growth and device properties will be discussed further.