Self-limited oxide formation in Ni(111) oxidation

Abstract

The oxidation of the Ni(111) surface is studied experimentally with low energy electron microscopy and theoretically by calculating the electron reflectivity for realistic models of the NiO/Ni(111) surface with an ab initio scattering theory. Oxygen exposure at 300 K under ultrahigh-vacuum conditions leads to the formation of a continuous NiO(111)-like film consisting of nanosized domains. At 750 K, we observe the formation of a nano-heterogeneous film composed primarily of NiO (111) surface oxide nuclei, which exhibit virtually the same energy-dependent reflectivity as in the case of 300 K and which are separated by oxygen-free Ni(111) terraces. The scattering theory explains the observed normal incidence reflectivity R(E) of both the clean and the oxidized Ni(111) surface. At low energies R(E) of the oxidized surface is determined by a forbidden gap in the k = 0 projected energy spectrum of the bulk NiO crystal. However, for both low and high temperature oxidation a rapid decrease of the reflectivity in approaching zero kinetic energy is experimentally observed. This feature is shown to characterize the thickness of the oxide layer, suggesting an average oxide thickness of two NiO layers.

A Simple Heterogeneous Catalyst for Phosphite Addition on Carbonyl Groups

“…27 by means of representing the surface region as a fragment of a repeated supercell. This has given rise to an all‐electron variational embedding method, which was applied to electron diffraction from a wide range of surfaces 32–37. This method aims at an accurate inclusion of the self‐consistent potential as obtained within the Density Functional Theory, and it is much less efficient for surface structure refinement.…”

Prüfung, Überwachung und Wartung von Litzenbündelseilen

“…Further examples for dynamic $ I(V)$ analysis of model catalysts are Ni(111) oxidation by O 2 34 and redox experiments on monolayer and bilayer Ag films on Ni(111) surfaces. Depending on local film thickness and temperature, NiO(111) formation concurring with Ag de‐wetting and Ag island thickening is observed.…”

Growth, magnetism and ferromagnetic thickness gap in Fe films on the W(111) surface

“…The differences between the experiment and expected peak positions (4.71 eV for W and 4.31 eV for Fe) are contributed to by the work function of the LaB 6 cathode (2.7 eV) and by the self-correction energy, 32 which is of the order of 1 to several eV, e.g., 1.6 eV for Ni. 33 Similarly, the peak developing strongly above 1 ML initially at about 25.0 eV is consistent (with similar offset) with the bulk-forbidden (111) Bragg peak of a bcc Fe(111) layer that is vertically contracted and laterally (tensile) strained to lattice match to the W(111) substrate, 34 which is expected at 19.98 eV. An fcc Fe(111) layer 34 can unambiguously be ruled out because its first allowed Bragg peak, i.e., (111), is expected at a considerably lower energy of 8.63 eV.…”