MICROWAVE MEASUREMENT OF THE DIELECTRIC-CONSTANT OF SR0.5BA0.5TIO3 FERROELECTRIC THIN-FILMS

Measurement of the relative dielectric constant of a Sr0.5Ba0.5TiO3 (SBT) thin film is presented as a function of electric field strength and temperature over a broad frequency range using a microstrip transmission line. The transmission line was fabricated from a trilayer structure where the SBT film, grown by pulsed laser deposition, was bounded by silver and platinum metallization layers. Such structures involving ferroelectric films could be useful for microwave applications because of the substantially smaller bias voltages (almost-equal-to 1-10 V) compared to those required for bulk material. The SBT film was found to exhibit a dielectric constant of almost-equal-to 120-250 and a large electric field modulation of almost-equal-to 50% at 200 kV/cm. These properties of the material as well as the Curie temperature are compared to those of bulk SBT.