Study of the W (Ta) core level shifts induced by the adsorption of oxygen on tungsten (tantalum) (110)

The authors present new experimental XPS spectra of 4f7/2 levels of tungsten in the W(110)-O system and a theoretical model in which the change of the binding energy of core levels of W atoms bound to O is due to a small charge transfer from these atoms towards oxygen. The same analysis is done for a Ta(110)-O system. Finally, using thermodynamical arguments, they link the displacements of core levels to the variation of the binding energy of O along the transition series and show that they always correspond to larger binding energy.