La doped Ba1−xSrxTiO3 thin films for tunable device applications

• Published in: Journal of applied physics 2001-06, Vol.89 (11), p.6336-6340
• Main Authors: Cole, M. W., Joshi, P. C., Ervin, M. H.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.1366656

Pure and La doped Ba0.6Sr0.4TiO3 thin (BST) films were fabricated via the metalorganic solution deposition technique using carboxylate-alkoxide precursors on Pt–Si substrates. The La doping concentration, from 0 to 10 mol %, was found to have a strong influence on the 750 °C postdeposition annealed films material properties. All films possessed a nontextured polycrystalline microstructure with no evidence of secondary phase formation. The pure and 1 mol % La doped films exhibited a uniform microstructure suggestive of a fully developed film at this annealing temperature. Improved dielectric and insulating properties were achieved for the 1 mol % La doped BST thin films with respect to that of undoped BST films. The 1 mol % La doped BST film exhibited a lower dielectric constant, (283 vs 450) and enhanced resistivity (31.4×1013 Ω cm vs 0.04×1013 Ω cm) with respect to that of undoped BST films. The loss tangent and tunability (at 100 kHz) of the 1 mol % La doped BST films were 0.019% and 21% (at E=300 kV/cm), respectively. Films doped at concentrations between 5 and 10 mol % possessed under developed microstructures suggesting that higher annealing temperatures and/or longer annealing times are required. The single phase structure of the 5–10 mol % La doped BST films, combined with the beneficial influence of the 1 mol % La doping on the BST films dielectric and insulating properties, suggest potential for further enhancement of the films material properties after optimization of the thermal treatments for the 5–10 mol % La doped BST thin films.