Abstract:
Adsorption of oxygen has been studied on (111), (110) and (100) surfaces of Ag, Cu, and Ni employing XPS and UPS. Besides atomic species with an O(1s) binding energy of ~ 530 eV, molecular adsorption is found on all the three Ag surfaces associated with a characteristic O(1s) binding energy of 532 eV. He II spectra show a feature around 2.5 eV due to the molecular species. Molecular adsorption is also found on all the three surfaces of Cu with a characteristic binding energy of 533 eV. He II spectra show characteristic features due to molecular adsorption on these surfaces at 100 K. The proportion of molecular species is maximum on the (111) surfaces and least on the (110) surfaces of both Ag and Cu. On Ni surfaces, there is no molecular adsorption; a unique O(1s) feature ascribed to O1− species is found at 531 eV. The intensity of this feature does not vary significantly with temperature in contrast to the O(1s) feature due to the molecular species on Ag and Cu surfaces.
