Fine structures of energy losses and Auger electrons. Determination of the local order of the Co/Si(111) interface

The thesis manuscript describes three recent techniques developed in the laboratory and applied to the study of the local order and unoccupied state densities of Co/Si(111) interfaces and various cobalt silicides. - By observing the fine structures that appear in electron energy loss spectra beyond ionization thresholds (E.E.L.F.S. technique), we show that it is possible to access interatomic distances at the surface and interfaces of solids. We have applied this technique to the study of the early stages in the formation of the Co/Si(111) interface and various cobalt silicides (CoSi₂, CoSi, Co₂Si) on Si(111). - Analysis of the ionization threshold in loss spectra (E.E.L.N.E.S. technique) provides access to the density of unoccupied states above the Fermi level, in a complementary way to photoemission of occupied states. Our preliminary results obtained on the Co/Si(111) interface and on cobalt silicides show that this technique is very promising and deserves to be developed further - The study of Auger spectra has enabled us to highlight a new phenomenon called E.X.F.A.S. which leads to the determination of the interatomic distance at the surface of certain materials. We present our experimental results for Fe, Ni, Co and Cu, and suggest an interpretation of the physical mechanisms involved