Title: A Surface Spectroscopy Study of U Overlayers on Graphite.
Authors: GOUDER ThomasCOLMENARES C.a.NAEGELE Jochen rainier
Citation: Surf. Sci. vol. 342 p. 299-306
Publication Year: 1995
JRC N°: JRC11907
URI: http://publications.jrc.ec.europa.eu/repository/handle/JRC11907
Type: Articles in periodicals and books
Abstract: X-ray and ultra violet photoelectron spectroscopies have been used to study U overlayers deposited on graphite by magnetron and straight diode sputtering. We investigated the mode of growth, the electronic structure of the U phase and overleyer-substrate reactions after deposition and annealing. At submonolayer coverage U deposits as clusters pointing to a low overlayer-substrate interaction. With increasing dosage, U clusters agglomerate forming eventually a continuous U overlayer. At low U dosage, U4f and valence band spectra exhibit correlation satellites which are attributed to the narrowing of the 5f bands and eventual 5f localization, because of the decreased coordination of U atoms. In thicker overlayers these satellites are missing showing U to have the same electronic structure as in bulk U metal. Even immediately after deposition some of the surface carbon loses its graphite character and becomes carbidic, which is mainly attributed to a weak interaction between surface U and the graphite substrate. Annealing at 600*C results in further reaction between U and graphite and leads to the formation of UC.
JRC Directorate:Nuclear Safety and Security

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