A PHOTOEMISSION-STUDY OF ULTRATHIN URANIUM LAYERS ON NOBLE-METALS

The core levels and valence states of ultrathin uranium layers on gold and nickel substrates have been studied using XPS. Uranium coverage w as less than 2.8 Angstrom which corresponds to less than one monolayer . The spectral features are very similar to those of intermetallic com pounds of uranium and gold or nickel. This indicates intermixing of de posited uranium with the substrates, at room temperature. In both U/Au and U/Ni systems, the main lines of U 4f spectra are quite asymmetric , and exhibit satellites at higher binding energies compared to the ma in lines. The profiles of the satellites are different in U/Au and U/N i, reflecting the difference of the hybridization between U 5f and val ence electrons of substrates.