Mn-doped BaTiO₃ thin film sintered using nanocrystals and its dielectric properties

BaTiO₃ thin films homogeneously doped with Mn were prepared by a novel powder-sintering thin-film process. Mn-doped BaTiO₃ nanocrystals 5-7 nm in diameter were synthesized by a sol-gel method and sintered to form a highly densified microstructure containing columnar grains epitaxially grown on a (111)-oriented Pt/TiO₂/Al₂O ₃ substrate at a low temperature of 800 °C. On the basis of the results of various structural analyses, Mn was suggested to act as an acceptor in the perovskite structure of BaTiO₃, which was also supported by the experimental finding indicating that the leakage current density was significantly improved compared with that of a nondoped BaTiO₃ thin film. Moreover, the dielectric constant of the Mn-doped BaTiO₃ thin film, 728 at 10 kHz with a loss tangent of 1.3%, was higher than that of the nondoped BaTiO₃ thin film, probably owing to the electrostrictive effect induced by in-plane tensile stress. These results clearly indicate the feasibility of using doped BaTiO₃ nanocrystals in the powder-sintering thin-film process for improving dielectric properties.