Elastic and inelastic contributions to the XPS photoelectron diffraction patterns of Ni(100) and NiO(100)

Abstract

XPS spectra of Ni(100) and NiO(100) single crystals, measured as a function of the polar angle in the [100]-[010] emission plane, are successfully decomposed into their elastic (intrinsic spectrum) and inelastic contributions using the background subtraction procedure as proposed by Tougaard et al. [Phys. Rev. B 25 (1981) 4452; Surf. Interface Anal. 11 (1988) 453; J. Electron Spectrosc. Relat. Phenom. 52 (1990) 243], with an electron energy loss function deduced from experimental electron energy loss spectra. The inelastic background correction factor shows a diffraction pattern which anticorrelates nearly linearly to the photoelectron diffraction pattern of the intrinsic spectrum, that is its maxima and minima coincide with the minima and maxima of the latter. This behaviour can be described by a simple model, based on heuristic arguments on inelastic and elastic losses and “defocusing” due to multiple scattering along densely packed rows of atoms in the lattice. The consequence of different background subtraction procedures on the shape of the XPS diffraction pattern and for the quantification of XPS data is discussed.