A photoemission study of the interaction of Ni(100), (110) and (111) surfaces with oxygen

• Published in: Surface science 1977, Vol.65 (1), p.13-36
• Main Authors: Norton, P.R., Tapping, R.L., Goodale, J.W.
• Format: Article
• Language: English
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/0039-6028(77)90289-8

Photoelectron spectroscopic studies of the oxidation of Ni(111), Ni(100) and Ni(110) surfaces show that the oxidation process proceeds at 295 and 485 K in two distinct steps: a fast dissociative chemisorption of oxygen followed by oxide nucleation and lateral oxide growth to a limiting coverage of 3 NiO layers. The oxygen concentration in the 295 K saturated oxygen layer on Ni(111) was confirmed by 16O(d,p) 17O nuclear microanalysis. At 295 and 485 K the oxide growth rates are in the order Ni(110) > Ni(111) > Ni(100). At 77 K the oxygen uptake proceeds at the same rate on all three surfaces and shows a continually decreasing sticking coefficient to saturation at ~2.1 layers (based upon NiO). An O 1 s b. e. = 529.7 eV is associated with NiO, and O ls b.e.'s of ~531.5 and 531.3 eV can be associated, respectively, with defect oxide (Ni 2O 3) or (in the presence of H 2O) with an NiO(H) species. The binding energies (Ni 2p, O 1s) of this NiO(H) species are similar to those for Ni(OH) 2. Defect oxides are produced by oxidation at 485 K, or by oxidation of damaged films (e.g. from Ar + sputtering) and evaporated films. Wet oxidation (or exposure to air) of clean nickel surfaces and oxides, and exposure of thick oxide to hydrogen at high temperature results in an O 1s b.e. ~531.3 eV species. Nuclear microanalysis 2H( 3He,p) 4He indicates the presence of protonated species in the latter samples. Oxidation at 77 K yields O 1s b.e.'s of 529.7 and ~531 eV; the nature of the high b.e. species is not known. Both clean and oxidised nickel surfaces show a low reactivity towards H 2O; clean nickel surfaces are ~10 3 times less reactive to H 2O than to oxygen.