Using synchrotron radiation, W 4f7/2 and valence-band photoelectron spectroscopy was used to study the oxidation states of the p(3 x 1) reconstructed surface of W(100) produced by oxygen adsorption at 1500K. The W 4f7/2 study showed two features at 0.40 and 1.50eV higher binding energies relative to the bulk feature which represented shifts to lower binding energies compared to the W 4f7/2 features of the as-grown oxygen films on W(100). Co-existence of these features was a characteristic of the formation of the p(3 x 1) structure. The valence-band studies of this system and as-grown oxygen films at room temperature showed an oxygen-induced feature for the p(3 x 1) structure for which the peak maximum had shifted by 0.9eV to higher binding energies compared to the as-grown films. The direction of shifts in the W 4f7/2 and valence-band spectra for the p(3 x 1) structure confirmed the reduction of the charge transfer from W to oxygen compared to the as-grown films. A study of the valence-band changes with photon energy showed that the main component of the oxygen-induced feature in the p(3 x 1) VB at 6.6eV was related to a hybridized state between W 5d and O 2p electrons.

Valence Band and Surface Core-Level Shift Studies of the Oxygen-Induced p(3 x 1) Reconstruction of the W(100) Surface. N.Moslemzadeh, S.D.Barrett: Surface Science, 2006, 600[11], 2299-304