Novel tunable acceptor doped BST thin films for high quality tunable microwave devices

Abstract

The materials properties of undoped and low concentration Mg doped Ba$_{0.6}$Sr$_{0.4}$TiO$_{3}$ (BST) thin films are reported. The films were fabricated on single crystal (100) MgO and Pt coated Si substrates via the metalorganic solution deposition (MOSD) technique using carboxylate-alkoxide precursors and post-deposition annealed at 800$^\circ$C (film/MgO substrates) and 750$^\circ$C (film/Pt-Si substrates). The dielectric properties were measured at 10 GHz using unpatterned/non-metallized films via a tuned coupled/split dielectric resonator system and at 100~kHz using metal-insulator-metal capacitors. The structure, microstructure, surface morphology and film/substrate compositional quality were analyzed and correlated to the films dielectric and insulating properties. The Mg doped BST films exhibited improved dielectric loss and insulating characteristics compared to the undoped BST thin films. The improved dielectric properties, low leakage current, and good tunability of the low level Mg doped BST thin films merits strong potential for utilization in microwave tunable devices.