Reactive Oxidation Induced Stoichiometric Modulation of Multivalent Vanadium Oxides

Vanadium oxides, such as V₂O₃, VO₂, and V₂O₅, have attracted considerable attention because of the fascinating physical properties of each oxidation state. On the other hand, precisely controlling the individual oxidation states is difficult due to the sensitivity of oxygen stoichiometry. This article reports that reactive oxygen annealing (ROA) can systematically change the oxidation state of the vanadium oxide films grown on a c-Al₂O₃ substrate compared with typical annealing under O₂ environments. Chemical, structural, electronic, and electrical analysis confirms the evolution of the vanadium oxide phases from V₂O₃ to V₂O₃/VO₂, VO₂, VO₂/V₂O₅, and V₂O₅, showing that the ROA method can control and tune the oxidation state of the highly oxygen-sensitive multivalent metal oxides.