Surface effects in the Ni2px-ray photoemission spectra of NiO

Abstract

We report experimental and theoretical evidence of surface effects in the Ni 2p x-ray photoemission spectra ͑XPS͒ of NiO. The Ni 2p 3/2 surface-enhanced XPS of a NiO sample show a relative enhancement of the intensity of the known satellite at 1.5 eV higher binding energy from the main line, indicating a considerable surface contribution of this satellite. The results are discussed in terms of bulk-octahedral and surfacepyramidal Ni symmetries. Other contributions, like nonlocal screening effects, cannot be neglected.

Passivation of the La2NiMnO6 double perovskite to hydroxylation by excess nickel, and the fate of the hydroxylated surface upon heating

“…9 is empirical in nature, based on the minimum four peaks needed to reproduce the 2p 3/2 satellite peak shape and that the charge-transfer formalism, while useful in relating photoemission to the electronic nature of the cation, is an oversimplified construct. Multiplet structure [41,42], plasmon resonance [43] and surface effects [44] have all been reported to contribute to the Ni 2p photoemission peak shape, not all of which present resolvable features.…”

Ni–Ta–O mixed oxide catalysts for the low temperature oxidative dehydrogenation of ethane to ethylene

“…However, there is disagreement in the literature on the origin of the satellite I of the low energy band of Ni2p3/2. It has been ascribed to the presence of Ni 3+ , Ni 2+ -OH species, Ni 2+ vacancies or a non-local screen mechanism [44][45][46] and was recently assigned to a surface effect [47]. The satellite I to Ni2p3/2 intensity ratio varies from 2 to 2.6 in the samples prepared by SS synthesis, which is much higher than the value of around 1.5 shown by those prepared by SG synthesis.…”

Interface effects in theNi2px-ray photoelectron spectra of NiO thin films grown on oxide substrates

“…1, comes from the pyramidally coordinated Ni atoms at the NiO surface. 2 This surface effect has been explained in terms of cluster model calculations with reduced symmetry in which the c គ3d 9 L គ line calculated for a NiO 5 cluster ͑pyramidal symmetry͒ shifts by 1 eV to higher binding energies with respect to the same line calculated for a NiO 6 cluster ͑octahedral symmetry͒. The reduced symmetry model also predicts a splitting of the unoccupied Ni e g states at the NiO surface.…”