Preferred crystal orientation of sol-gel derived Bi4-xLaxTi3O12 thin-films on silicon substrates

Polycrystalline thin films of La-substituted bismuth titanate (BLT) have been formed directly on p-type Si(100) substrates by using sol-gel and spin-coat methods. The BLT film and interfacial layer between BLT and Si were quantitatively investigated by X-ray reflectivity method. Also, crystal orientations of sub-100 nm-thick BLT thin films have been confirmed by X-ray diffraction using synchrotron radiation source. The preferred c-axis orientation along the normal to the surface depended on the crystallization temperature. The difference in the preferred c-axis orientations of the BLT films caused the difference in the hysteresis voltage width in the capacitance-voltage characteristics of Au/BLT/p-Si structures. Furthermore, c-axis of Bilayered structure was preferentially oriented and aligned in the in-plane direction.