A DETAILED XPS STUDY OF THE RARE-EARTH COMPOUNDS EUS AND EUF3

Eus and EuF3 powder samples have been the subject of an extensive XPS study. For both compounds, the valence state of Eu was examined, toget her with its stability, with respect to X-ray dose, total exposure tim e under XPS ambient (UHV) and XPS sputter time. Maximum likelihood com mon factor analysis (MLCFA) has been applied in combination with XPS s putter profiling to determine the correct number of chemical states pr esent in the sample. In this context, the mixed-valence behaviour of E u in these compounds is discussed. Furthermore, an explanation for the XPS final state effects in the Eu3d, Eu4d and Eu4f photoionisation pr ocess is proposed.