Structures and properties of La- and Sm-doped BaTiO3 sputtered films: Post-annealing and dopant effects

Abstract

$200\text{-}\mathrm{nm}$ -thick La- and Sm-doped $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_3$ thin films with $A∕B$ ratio of unity fabricated by magnetron sputtering on the $\mathrm{Pt}∕\mathrm{Ti}∕\mathrm{Si}{\mathrm{O}}_2∕\mathrm{Si}$ substrate have been characterized. The effects of post-annealing and the amount of dopant on structure and electrical properties were studied. X-ray diffraction studies reveal that the films annealed at $750°\mathrm{C}$ show tetragonal $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_3$ crystal structure without any detectable second phase formation. X-ray photoelectron spectroscopy results confirm that La substitutes the $A$ site and Sm is in the $B$ site in lightly doped films. ${\mathrm{La}}_2{\mathrm{O}}_3$ or ${\mathrm{Sm}}_2{\mathrm{O}}_3$ is present in the $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_3$ structure when the dopant content is more than $1.4\mathrm{at.}\%$ La or 1.0% Sm. The permittivity increases with increasing annealing temperature up to $750°\mathrm{C}$ due to the coarse grains and better crystallinity. The leakage current property is found to vary with the type of dopant.