An Elegant Low-cost Materials Solution for Achieving Low Insertion Loss, Affordable Tunable Filters for Next Generation Mobile Communications Platforms

Report No. ARL-TR-4811
Authors: M. W. Cole, E. Ngo, and R. J. Tan
Date/Pages: April 2009; 18 pages
Abstract: The effect ultraviolet (UV)-assisted annealing on the structural, dielectric, and insulating properties of barium strontium titanate (BST) thin films was investigated. The material properties of BST films, prepared by RF sputter deposition, annealed via conventional thermal annealing and UV-assisted thermal annealing process protocols were compared and evaluated. The x-ray diffraction results showed contracted lattice constants and enhanced crystallinity for the RF sputtered BST films annealed via the UV-assist treatment. Isothermal-temporal annealing experiments, over a broad range of annealing times ~12 to 225 min, revealed that the films annealed utilizing UV-assist possessed enhanced crystallization, and lattice parameters closer to bulk values with respect to the conventional thermal annealed films. The dielectric loss and leakage current density of the films, evaluated from 0 to 8V, was significantly reduced by employing UV-assisted annealing. The improved dielectric loss and leakage characteristics were attained without degradation of film tunability, hence material property balance was sustained. Mitigation of oxygen vacancies, associated with the UV-assisted annealing, is deemed responsible for the improvement of the dielectric and electrical properties of the BST thin films.
Distribution: Approved for public release
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Last Update / Reviewed: April 1, 2009