Abstract
La-substituted bismuth titanate (BLT) thin films formed directly on Si(IOO) substrates by using sol-gel methods have shown ferroelectric property and a preferred c-axis orientation depending on crystallization temperature. Since the spontaneous polarization and leakage current of BLT thin film strongly depend on the crystal orientation and it affects the electrical characteristics of the thin film memory devices, the investigation of orientation in the BL T film is important for the memory device development. X-ray diffraction analysis clearly showed the change in the c-axis orientation of the BL T film during the crystallization at 600 °C. The 00/ diffraction from the crystal the c-axis of which was normal to the surface was slightly observed in the sample crystallized for 5 minutes at 600 °C, and the diffraction peak clearly appeared after 10 min and then the intensity decreased gradually. In contrast to this behavior, the in-plane c-axis orientation was clearly seen in the BL T crystallized only for 5 minutes and it was almost independent of the crystallization duration. The X-ray reflectivity analysis showed that the ~ 1 nm-thick interface layer was formed by 10 minutes at 600 °C. The in-plane c-axis orientation could be related to the crystal structure of silicon, and the formation of the preferred orientation might compete with the interface layer formation at the early stage of crystallization.
