XPS OBSERVATIONS OF THE ACCELERATED OXIDATION OF NIOBIUM IN THE PRESENCE OF IRON

A NbO film (similar to 8 Angstrom thick) deposited on a gold substrate is shown by XPS to be relatively inert to a H-2/H2O treatment. Howeve r, when the same treatment is made following the deposition of iron (l ayer similar to 12 Angstrom thick), the NbO shows a much enhanced reac tivity; it is converted to a higher oxide while the Fe converts to Fez 03. Heating this sample to 300 degrees C under UHV conditions caused a more complete conversion of NbO to a NbO2-like oxide, while simultane ously the Fe2O3 is reduced to FeO. Further heating at 500 degrees C yi elded a pure Nb2O5 film, while the FeO appears to reduce to the metall ic form which then dissolves into the gold.