Ferroelectric properties of lanthanide-substituted Bi4Ti3O12 epitaxial thin films grown by metalorganic chemical vapor deposition

The ferroelectricity of epitaxially grown lanthanide-substituted Bi4Ti3O12, (Bi(4-x)Ln(x))Ti3O12 (Ln = La, Nd, and Sm) thin films with various lanthanide contents (x) was systematically investigated; (104)-oriented epitaxial (Bi(4-x)Ln(x))Ti3O12 thin films were grown on (111)SrRuO(3)parallel to(111)SrTiO3 substrates by metalorganic chemical vapor deposition. The remanent polarization (Pr) increased with x irrespective of the kind of lanthanide element. The maximum Pr values were 17, 25; and 20 muC/cm(2) for (Bi3.44La0.56)Ti3O12, (Bi3.54Nd0.46)Ti3O12, and (Bi3.87Sm0.13)Ti3O12 thin films, where the coercive field (Ec) values were 145, 135, and 135 kV/cm, respectively. Reduction in the Pr values due to the excess substitution of the lanthanide is considered to originate from the solubility limit of the lanthanide in the Bi site in the pseudoperovskite layer. The Nd-substituted film with the largest polarization is comparable to the commercially used Pb(Zr,Ti)O-3 films and is a useful candidate for lead-free ferroelectric applications. (C) 2003 American Institute, of Physics. [DOI: 10.1063/1.1536010].