QUANTITATIVE XPS OF NIO, COO AND MNO - THE EFFECTS OF ELASTIC AND INELASTIC ELECTRON-SCATTERING

In order to check whether the method for background correction developed by Tougaard can be applied to oxides we measured XPS spectra of single crystalline NiO, MnO and CoO samples. The materials for which background treatment was developed and tested originally were metals and alloys. In contrast to that, the oxides we study in the present work are insulators. We have chosen these compounds because their structure is simple and by cleaving them in vacuo it is possible to obtain surfaces with well-defined stoichiometry. The inelastic background for these oxides is likewise described well by the above mentioned model. The ratio of metal to oxygen concentration calculated from the XPS intensities so obtained oscillates around 1.0 with a maximum deviation of about +/- 20% in the worst case. These deviations originate from elastic electron scattering, namely forward focusing (X-ray photoelectron diffraction). Taking this into account, the perfect stoichiometry is obtained within a few percent.