Interfacial Reactivity at the Interfaces of Titanium-Cobalt oxides*

The chemical reactivity at the titanium-cobalt oxides has been investigated by the technique of x-ray photoelectron spectroscopy. Elemental cobalt was oxidized by two different processes: one in vacuum chamber and the other in a quartz tube furnace. These processes yielded the CoO and Co₃O₄ phases of the cobalt oxides. Thin films of titanium were deposited on these oxides kept at room temperature. Changes in the spectral features (such as the binding energy and the presence of the satellites) have been utilized to ascertain the nature of chemical reactivity at the Ti-cobalt oxide interfaces. The titanium overlayer has been observed to get oxidized resulting in the formation of TiO₂. The cobalt oxides were observed to get reduced. The CoO was observed to get reduced to elemental Co. In the case of Co₃O₄ substrate, the oxide first gets reduced to CoO for thin films of the titanium overlayer.  The reactivity has also been investigated for these interfaces as a function of substrate temperature.