AVS 49th International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP25
Synchrotron Radiation X-ray Photoelectron Spectroscopy Study of Thermal Effects on Nb Surface Oxides@footnote 1@

Tuesday, November 5, 2002, 5:30 pm, Room Exhibit Hall B2

Session: Surface Science Poster Session
Presenter: Q. Ma, Argonne National Laboratory
Authors: Q. Ma, Argonne National Laboratory
P. Ryan, Argonne National Laboratory
J. Freeland, Argonne National Laboratory
R.A. Rosenberg, Argonne National Laboratory
Correspondent: Click to Email
We report a recent x-ray photoelectron spectroscopy study of thermal effects on the oxides grown in air on crystalline Nb surfaces. Both angle-resolved and glancing-incidence x-ray photoelectron spectroscopy techniques were used in this study. The samples were annealed at 430 °K and 540 ° K for various lengths of time. We will demonstrate that the reduction of the insulating Nb@sub2@O@sub5@ layer to lower oxidation states is primarily an interface-mediated reaction. Annealing at 430 °K produces a semiconducting, layered oxide with a composition of NbO@subx@ that changes from x = 2.5, 2.0, 1.5, 1.0, to 0.5 across the oxide. Annealing at 540 °K produces a metallic oxide layer with a composition that is mainly NbO@sub0.5@, but changes continuously and rapidly near the oxide surface. A photoelectron diffraction effect is observed on the 540-K annealed surface, which possibly indicates the formation of an ordered, but faceted, oxide layer. Oxygen readily diffuses into the Nb substrate by annealing at 540 °K. However, oxygen diffusion proceeds predominantly within the oxide in the case of annealing at 430 °K. @FootnoteText@ @footnote 1@This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38.