Defect states at the TiO2(110) surface probed by resonant photoelectron diffraction.

The charge distribution of the defect states at the reduced TiO(2)(110) surface is studied via a new method, the resonant photoelectron diffraction. The diffraction pattern from the defect state, excited at the Ti-2p-3d resonance, is analyzed in the forward scattering approach and on the basis of multiple scattering calculations. The defect charge is found to be shared by several surface and subsurface Ti sites with the dominant contribution on a specific subsurface site in agreement with density functional theory calculations.

Quadrupolar transitions evidenced by resonant auger spectroscopy.

From absorption spectra, the only way to bring to the fore the occurrence of quadrupolar transitions is to study their angular dependence. Resonant spectroscopies offer a new opportunity to obtain more insight into excited electronic states by studying lineshape and intensity of decay processes. We show here that resonantly excited Ti KL(2,3)L(2,3) Auger spectra of TiO2(110) carry a clear signature of quadrupolar transitions to localized e(g) and t(2g) d-like states, giving access to a direct measurement of crystal field splitting.

Surface EXAFS study of metastable magnetic thin films.

Epitaxial thin films provide new opportunities to explore the relationship between structure and magnetism. The bidimensionnal character of magnetic films deposited on single-crystal substrates and the occurrence of singular crystallographic structures often confer on these systems electronic and magnetic properties that cannot be found in the bulk solids. Although shape anisotropy would favour an in-plane easy axis of magnetization for thin films, Ni layers deposited on Cu(001) present a perpendicular magnetic anisotropy in a very wide thickness range.