INITIAL-STAGES OF COBALT OXIDATION BY FTIR SPECTROSCOPY

The behaviour of specular reflectance of cobalt oxides on metal has been studied theoretically (CoO/Co system) and experimentally (Co3O4/CO system; the thin films are obtained by chemical spray pyrolysis) in the infrared region. CoO may be identified by a LO mode at 585 cm-1 and by a TO mode at 345 cm-1 . Co3O4 is characterized by five bands respectively at 690 (LO), 660 (TO), 605 (LO), 560 (TO) and 390 cm-1. These experimental results allow the characterization of CoO and Co3O4 grown on metal during the initial stages of thermal oxidation (400-750-degrees-C). For film thicknesses in the range 10-1000 nm, the amounts of CoO and Co3O4 in the duplex structure layers may be estimated by FTIR reflectance spectroscopy. FTIR and XRD studies reveal a cyclic behaviour in the growth of the Co3O4/COO/CO system.