OPTICAL STUDY OF NIOBIUM DISILICIDE POLYCRYSTALLINE FILMS

NbSi2 polycrystalline films, coevaporated and thermally annealed, were subjected to chemical and structural characterization, and then studied by reflectance from 0.06 to 6 eV and ellipsometry from 1.4 to 5 eV. The dielectric functions, obtained from Kramers-Kronig analysis and directly from ellipsometry, are also presented. Low-frequency free-carrier response is discussed in terms of the Drude model; the high-frequency interband structures are interpreted on the basis of the calculated density of states and photoemission results. A comparison is made with the optical properties of isoelectronic VSi2 and TaSi2 Polycrystalline films.