Evidence for the 5f localisation in thin layers
European Commission, Joint Research Centre, Institute for
Transuranium Elements P.B. 2340, D-76175 Karlsruhe,
2 Department of Electronic Structures, Charles University Ke Karlovu 5, CZ-121 16 Prague 2, Czech Republic
Accepted: 11 June 2001
High-purity ultrathin layers of deposited on were studied by X-ray photoelectron (XPS) and high-resolution valence band (UPS) spectroscopy. The itinerant character of the 5f states is gradually lost with reduced thickness, and the localised 5f states, which appear as a broad peak 1.6 below the Fermi level, were observed for one monolayer. At intermediate thickness three narrow peaks appear close to the Fermi level, which are identical to features observed in and other materials. A comparative study of bulk α- indicates a surface re-organisation yielding more localised f-electrons at conditions of thermodynamic equilibrium.
PACS: 71.20.Gj – Other metals and alloys / 71.28.+d – Narrow-band systems; intermediate-valence solids / 79.60.-i – Photoemission and photoelectron spectra
© EDP Sciences, 2001