OPTICAL FUNCTIONS OF EPITAXIAL BETA-FESI2 ON SI(001) AND SI(111)

We accurately measured the complex refractive index and dielectric fun ctions from 0.2 to 5 eV of high-quality beta-FeSi2 epitaxial films, wi th thicknesses ranging from 100 Angstrom to 8000 Angstrom, grown on Si (001) and Si(lll) using two different techniques. Reflectance, transmi ttance and spectroscopic ellipsometry were used and the spectra were a nalyzed within a multilayer model, by checking the Kramers-Kronig cons istency of the derived optical functions. These functions, compared wi th previous results for polycrystalline samples, showed a very good ag reement with those obtained for bulk samples and a significant differe nce to films. The nature (direct or indirect) of the lowest optical ga p and the effects of the film thickness and the substrate orientation on the optical response were also investigated.