Adsorption-induced surface valence changes in europium intermetallics

Mårtensson, N. ; Hillebrecht, F. U. ; Sarma, D. D. (1985) Adsorption-induced surface valence changes in europium intermetallics Surface Science, 152-153 . pp. 733-742. ISSN 0039-6028

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The trivalent compounds EuPd3 and EuNi5 have been studied with X-ray excited Photoelectron Spectroscopy (XPS) and Bremsstrahlung Isocromat Spectroscopy (BIS). Due to the very small contribution from empty Pd or Ni d states in these compounds, BIS gives a clearer view of the Eu 4f states than the XPS valence electron spectra. In the BIS spectra as well as in the core level spectra we find contributions from a divalent surface layer. It is concluded that there is a substantial surface disproportionation of the compounds with an increased Eu concentration at the surface. Controlled oxidation showed that the divalent spectral features disappear at 1-2 L of oxygen, indicating that trivalent oxides are formed. Furthermore, we conclude that shake-down processes are not important in core level spectra from Eu compounds, in contrast to previous findings.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
ID Code:46431
Deposited On:04 Jul 2011 11:35
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