AN AES, UPS AND HREELS STUDY OF THE OXIDATION AND REACTION OF NB(110)

The oxidation of Nb(110) upon oxygen adsorption has been investigated using AES, UPS and HREELS. For low and medium exposures of oxygen, two new loss features at 720 and similar to 950 cm(-1) develop, which are assigned to Nb-O and Nb-O-Nb stretching vibrations, respectively. Whe n oxygen exposure is high, a broad and strong loss peak at 600-900 cm( -1) appears, which is due to bulk-like Nb-O-Nb stretching vibrations, the changes in the vibrational spectroscopy suggest that, with increas ing oxidation of the surface, NbO4 tetrahedra transform into NbO6 octa hedra. Experiments involving methanol adsorption further confirm these results concerning the process of oxidation.