CHARACTERIZATION OF RF-SPUTTERED IRON-OXIDE FILMS FOR MODELING PASSIVE FILMS

Iron oxide films were r.f.-sputtered on metallic, ceramic and polymeri c substrates in order to study the structure, composition and the phot o-electrochemical properties of the coatings. The formed iron oxide ph ase was Found to depend on the substrate biasing during deposition, Th e main phases obtained were alpha-Fe2O3 and Fe3O4. The films had 3 ten dency to form a columnar structure, which was more preferred on metall ic substrates. The alpha-Fe2O3 target was found to be reduced during t he sputtering, and a mixed oxide of alpha-Fe2O3 and Fe3O4 was formed. The orientation of the deposited films was found to be dependent on th e formed phase, the substrate voltage and the target composition. The deposition rate was dependent on the formed phase, biasing and substra te material, as well as on the level of the reduction of the target. T he films were nanocrystalline, having crystal sizes of 10 nm or less. The Fe2+ content was found to have an effect on the measured photocurr ents. Roughness of the semiconductor surface was noticed to have a str ong influence on the AC impedance of the sputtered oxide layers. X-ray absorption near edge spectroscopy (XANES) measurements revealed furth er information on the oxidation state of the sputter-deposited iron ox ide films. (C) 1998 Elsevier Science S.A.