Optical properties of Bi3.25La0.75Ti3O12 thin films using spectroscopic ellipsometry

Using spectroscopic ellipsometry, the optical properties of the Bi3.25La0.75Ti3O12 (BLT) thin films with different film thicknesses on platinized silicon substrates prepared by chemical solution methods have been investigated in the 400-1700 nm wavelength range. By fitting the measured ellipsometric parameter (Psi and Delta) data with a multilayer model system and the classical dispersion relation for the BLT thin films, the optical constants and thicknesses of the thin films have been obtained. Meanwhile, some degree of inhomogeneity (in the form of low density layers or surface roughness) has been found in the BLT thin films except for the thinnest film, which was homogeneous throughout its thickness. The multilayer model system became very complicated with increasing thickness. It indicated that the microstructure of the BLT thin films varied with increasing thickness. The refractive index n of the BLT thin films increases with increasing thickness, and on the contrary, the extinction coefficient k decreases with increasing thickness. The dispersion of the refractive index can be well explained by a single-term Sellmeier relation. (C) 2003 American Institute of Physics.