Photoemission study of the U/Si(111) interface

The electronic and geometric structures of thin uranium overlayers deposited on a clean Si(111)-(7×7) surface have been studied by X-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED). Three different stages of interaction between the deposited uranium and the silicon substrate are found, depending on the uranium coverage. A transition from localized to delocalized U 5f states is observed as the uranium thickness increases in the room-temperature depositions. Annealing of the substrate at 700°C results in clear spots in the LEED observations, suggesting the possible formation of ordered uranium silicide phases at the interface.