Preparation and photoelectron spectroscopy study of UNx thin films

Thin films of UN and U2N3 were prepared by reactive DC sputtering of U in N-2-containing atmosphere. The composition of the films was modified by varying the partial pressure of N-2. 4f-Core-level photoelectron spectra as well as valence-band spectra obtained with HeII and HeI photoexcitation confirm the itinerant character of the 5f-electronic states in UN, showing a high density of states at the Fermi energy. The 4f peaks in U2N3 are shifted towards higher binding energy and rue symmetric, indicating a low density of states at the Fermi level. Valence-band spectra show indeed a maximum of 5f emission at 0.8 eV below the Fermi level, but some 5f intensity at the Fermi level is preserved, contradicting full 5f localisation. (C) 2001 Elsevier Science B.V. All rights reserved.