OXIDATION OF Nb(001) STUDIED BY HIGH-RESOLUTION CORE-LEVEL PHOTOEMISSION

Abstract

Using high-resolution core-level photoemission with synchrotron radiation, we observed two suboxide states on the Nb(001) surface, which was heated in 1×10-6 Torr O 2 for several hours and then annealed several times at high temperatures in an ultrahigh-vacuum condition. These suboxide states were identified as Nb2O and NbO from the Nb3d5/2 core-level photoemission spectra. The relative amounts of these suboxide states varied with the annealing temperature, showing that at progressively higher temperatures more oxygen-deficient oxides were produced. Meanwhile, LEED patterns of the complex superstructures of the oxidized surfaces also changed. Many of these findings are analogous with other oxidized refractory metals.