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|Title:||A Surface Spectroscopy Study of U Overlayers on Graphite.|
|Authors:||GOUDER Thomas; COLMENARES C.a.; NAEGELE Jochen rainier|
|Citation:||Surf. Sci. vol. 342 p. 299-306|
|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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