Induced oxidation on Ni(111) by kinetic energy of O molecular beams

Teraoka, Yuden; Kawakami, Yasunori; Yoshigoe, Akitaka ; Harries, J.; Hiraya, Atsunari*

Chemical bonding states of oxygen, adsorbed on Ni(111) via supersonic O beams have been analyzed by low energy electron diffraction and synchrotron radiation X-ray photoemission spectroscopy. The oxygen-adsorbed structure in the early stages of O irradiation was assigned to be an three-folded near-fcc site. The oxide layer consisted of peroxide, suboxide, and NiO components depending on O incident energy and dose. In the 0.6 eV case, the three-folded near-fcc site changed finally to the NiO through suboxide and peroxide. The oxide layer was NiO(111) regardless of kinetic energy. With increasing kinetic energy, NiO formed in the lower O dose and the three-folded near-fcc sites decreased in the earlier stages. Especially, the kinetic energy of 2.3 eV was effective to form NiO in the extreme early stages. This implies that the activated adsorption occurs in the oxidation of Ni(111) by energetic O molecules.