Electron-Excited Auger-Electron Spectrum of aNi(110)−c(2×2)SSurface: Line-Shape Analysis and Correlation with Ion-Neutralization Spectroscopy

Abstract

Electron-excited Auger-electron spectra of a $\mathrm{Ni}\mathrm{}\left(110\right)\mathrm{}-c(2\mathrm{}\times 2)\mathrm{S}$ surface are correlated with the corresponding spectra obtained by ion-neutralization spectroscopy (data of Becker and Hagstrum). It is found that the sulfur $L_{2,3}\mathrm{VV}$ line is characterized by a threshold at 159 eV, a width ∼ 30 eV, and major peaks at 146 and 135 eV. The same structural features are found in both types of spectra, but different relative magnitudes of peak structure are observed. However, this difference may result in part from a fundamental assumption regarding the transition density function that was invoked to facilitate the comparison of the two types of spectra. The electron-excited spectroscopy yields information about levels deeper in the band than does the ion-neutralization spectroscopy due to the use of lower-lying core holes which provide relatively more potential energy for the Auger excitation. Calculations of Auger line shape from simple density-of-states models reveal how each pair of peaks in the latter gives rise to three peaks in the corresponding secondary-electron characteristic (Auger line shape) $N\left(E\right)\mathrm{}$, and how the background can produce a peak in $N\left(E\right)\mathrm{}$.