W(100)+O₂: Adsorption and reaction

Abstract

Adsorption and thermally stimulated reaction of oxygen on W(100) have been studied by ELS, LEED, ESD, and work function measurements. We have shown that ELS in tungsten provides a sensitive core orbital spectroscopy and have used it to map the behavior of the W 4f and 5p3/2 orbitals and the O 2s and 2p orbitals as a function of coverage and temperature. During adsorption of oxygen at T≲370 K, we observed sequential filling of electronically inequivalent bonding states in ELS and ESD. Heating of the oxygen‐dosed surface results in dramatic coverage‐ and temperature‐sensitive changes in the geometric structure, as evidenced by LEED, and in the electronic structure, as evidenced by ELS and ESD. Evidence of O 2s and W 5p3/2 orbital involvement in oxide formation is indicated. Extended oxidation results in strong shifts in the W 4f orbitals.