Effect of La substitution on electrical properties of highly oriented Bi4Ti3O12 films prepared by metalorganic chemical vapor deposition

The effect of La substitution on the electrical properties of Bi4Ti3O12 was investigated by using epitaxially grown Bi4Ti3O12 (BIT) films and highly oriented (B3.25La0.75)Ti3O12 [BLT] films with (001)-, (118)- and (104)(014)-orientations. By characterizing the leakage current density for films with different orientations, it was found that the leakage current density along the a-b plane was decreased by La substitution. The spontaneous polarization (P-s) of the BLT film evaluated from the P-E hysteresis properties of the (001)- and (118)-oriented films was 3.5 and 38 muC/cm(2) along the c-axis and the a-axis, respectively. They were smaller than those of the BIT films: 4.0 and 50 muC/cm(2). Based on the fact that La preferentially substitutes for the Bi site in the pseudoperovskite layer, the large remanent polarization widely reported for polycrystalline (Bi3.25La0.75)Ti3O12 films is related to the reduction of the number of defect complexes in the pseudoperovskite layer that possibly pin the domain motion.