Tunable ferroelectric thin film devices for microwave applications

Abstract

This work deals with the development of tunable microwave devices based on ferroelectric BaxSr1-xTiO3 (BST) thin films. Our work mainly includes improvement of dielectric properties, microwave characterization, integration of ferroelectric thin films for tunable microwave device applications. A reliable measurement method for microwave dielectric properties of parallel plate ferroelectric thin film varactor was presented. Effects of bottom electrodes on microwave dielectric properties of BST parallel plate varactors were investigated and a systematic comparison of the microwave properties of BST thin film varactors with parallel plate and interdigital electrodes was carried out. Three kinds of phase shifters: coplanar waveguide (CPW) transmission line, coupled microstrip line and composite right/left-handed transmission line (CRLH TL) were integrated on high resistance silicon substrates using BST thin film varactors with parallel plate electrodes, respectively. A dual-tunable trilayered structure composed of two BST layers and a BiFeO3 (BFO) layer was studied for microwave device applications.