Sammendrag
Sm overlayers in the monolayer regime, deposited onto a Nb(110) single crystal surface at room temperature, have been studied by means of high resolution photoelectron spectroscopy of the Nb 3d5/2 core level and the Sm valence band. In the sub-monolayer regime the Sm valence varies from mainly divalent for very low coverages to essentially trivalent close to the completed monolayer. Above one monolayer a new divalent component appears in the Sm 4f spectra, corresponding to divalent Sm in the second layer. The mixed valence in this over layer system is concluded to be heterogeneous (all Sm atoms have integer, but site-dependent valence). Sm forms ordered overlayers on Nb(110), and the Sm growth is consistent with a layer-by-layer growth mode (Frank-van der Merwe growth).
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