Thin films of cobalt oxides obtained by vacuum co-deposition of Co and TeO2

The composition and structure of thin films obtained by vacuum co-deposition of Co and TeO2 in an atomic ratio R-Co/Te = 1.5 are studied. It is shown that during the co-deposition a chemical reaction between both substances takes place resulting in the formation of amorphous CoO phase and elemental Te, very finely dispersed in the amorphous matrix. The reaction in as-deposited films proceeds until the complete oxidation of Co to Co2+. It is found that the crystalline phases of CoO, Co3O4 and/or Te are formed upon thermal heating of the films above 300degreesC. In this case, the reaction proceeds until complete consumption of TeO2 via the oxidation of Co2+ to higher valence and the formation of mixed oxides. (C) 2002 Elsevier Science Ltd. All rights reserved.