IN-PLANE DIELECTRIC PROPERTIES OF BST THIN FILMS GROWN ON MgO SUBSTRATES USING THE THIN PEROVSKITE LAYERS FOR MICROWAVE TUNABLE ELECTRONICS

Abstract

ABSTRACT Barium strontium titanate (BST) thin films have been intensively studied as a frequency and phase agile materials for the microwave tunable devices such as tunable filter, phase shifter and phased array antennas. In this work, we report on the epitaxial growth and the in-plane dielectric properties of (Ba, Sr)TiO3 (BST) thin films for high-performance microwave tunable device applications. Epitaxial BST thin films were deposited on MgO substrates by the insertion of thin perovskite ABO3 layer such as Ba(Zr, Ti)O3[BZT], Ba(Sn,Ti)O3 [BTS] and SrZrO3 [SZO], with an intermediate lattice constant between the BST films and the MgO substrate using a pulsed laser deposition. In-plane nonlinear dielectric properties of BST thin films were carried out using planar interdigitated (IDT) capacitor. The dielectric tunability and quality K-factor of BST thin film using thin BZT layer exhibited 78.8% and 150 at a frequency of 100 kHz and applied voltage of 40 V, respectively. These results indicate that the thin perovskite layer with an intermediate lattice constant between those of the BST film and the MgO substrate can be used as an excellent seed layer for improving the crystallization and dielectric properties of BST films, and that it is a promising candidate for high-performance microwave tunable devices at room temperature.