3dphotoemission study of the intermediate valence of Sm on Si(001)

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Abstract
Overlayers of Sm on Si(001) were studied by x-ray photoemission spectroscopy and low-energy electron diffraction. Divalent Sm was observed in the low-coverage region while an average valence of ∼2.75 was observed for monolayer coverage. It is concluded that except for very low coverages the variation of the Sm valence is controlled by direct Sm-Sm interaction. A comparison between the Sm-coverage dependence of 3d spectra and previously obtained 4f spectra gives further evidence to the view that photoemission from Sm core levels gives reliable information about the valence.