Synthesis and Optical Properties of Cobalt-Modified Titanium Oxide Films

Properties of polycrystalline TiO₂ films modified by magnetron sputtering of cobalt followed by pulsed photon-irradiation processing in air are investigated by methods of X-ray phase analysis, raster electron microscopy, atomic force microscopy, magnetic force microscopy, and IR spectroscopy. Formation of a nanocrystalline (with a grain size of ~50 nm) film consisting of cobalt and titanium oxides the surface of which exhibits magnetic properties is established in the process of modification. The IR reflectance spectra obtained at different angles of incidence in the region between 500 and 600 cm^–1 reveal the presence of two bands belonging to transverse modes (TO) and two corresponding bands belonging to the longitudinal modes (LO). These bands are indicative of formation of Co₃О₄ with spinel structure. Investigation of optical absorption suggests a predominant existence of phases characterized by direct interband transitions with energies of 1.43 and 1.83 eV for Co₃O₄, along with a transition with energy of 2.65 eV for cubic phase of CoO, in the films.