OPTICAL FUNCTIONS AND TRANSPARENT THIN-FILMS OF SRTIO3, BATIO3, AND SIOX DETERMINED BY SPECTROSCOPIC ELLIPSOMETRY

A procedure is presented for accurately determining the thickness, optical functions, and surface-roughness characteristics of thin-film insulators from two-channel spectroscopic polarization-modulation ellipsometry data. For films with minimal surface roughness, the optical functions can be determined over the entire measured spectrum; for rougher films, the analysis of the spectroscopic ellipsometry data yields meaningful values of the optical functions only in the transparent region. In general, the films must be transparent in a given range of wavelengths sampled by the ellipsometer so that at least two interference oscillations can be observed. The use of the procedure is illustrated with the determination of the optical functions of SrTiO3 and BaTiO3 thin films grown on MgO, and of SiO(x) films grown on Si. For SrTiO3 and BaTiO3, the thin-film results are compared with the measured optical functions of the respective bulk materials.