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 vary ing the partial pressure of N-2. 4f-Core-level photoelectron spectra as wel l as valence-band spectra obtained with HeII and HeI photoexcitation confir m 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 to wards 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 Fer mi level is preserved, contradicting full 5f localisation. (C) 2001 Elsevie r Science B.V. All rights reserved.