SPECTROSCOPIC ELLIPSOMETRY CHARACTERIZATION OF BA0.7SR0.3TIO3 THIN-FILMS PREPARED BY THE SOL-GEL METHOD

Spectroscopic ellipsometry (SE) was used to characterize Ba0.7Sr0.3TiO 3 (BST) thin films prepared by the sol-gel method. Ten samples were in vestigated, each consisting of a sol-gel BST thin film on Si substrate and annealed at 400, 500, 600, 700, and 800 degrees C, respectively, in O-2 and N-2 ambients. Our main objective was to determine the optic al properties of the BST thin films as a function of annealing tempera ture for annealing in the two chosen ambients, In the analysis of the measured SE spectra, a Cauchy dispersion function was used to represen t the optical properties of the BST thin films. For each sample studie d, good agreement was obtained between the measured spectra and the mo del calculations in the chosen spectral region. Our analysis clearly s hows that the refractive index of the BST films annealed in both ambie nts increases as the annealing temperature increases, with the index v alue of the films annealed in the O-2 ambient increasing more dramatic ally at temperatures above 600 degrees C, which, we believe, is an ind ication of further crystallization of the films. We confirmed this phe nomenon via X-ray analysis of the films. (C) 1998 Published by Elsevie r Science S.A.