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The reaction of Pd thin films evaporated in ultrahigh vacuum on a clean and Si-rich 6H-SiC(0001)(3×3) surface has been investigated in situ by low-energy electron diffraction (LEED) and photoelectron spectroscopy (UPS and XPS), and ex situ by atomic force microscopy (AFM) and glancing-incidence X-ray diffraction (GIXRD). For studying the interface formation, submonolayer amounts of Pd were sequentially deposited up to ∼20 A on the substrate maintained at room temperature. This deposit was subsequently annealed to 600–800 °C. At room temperature, Pd starts to react with SiC when the thickness attains ∼2.5 A, giving an interface Pd2Si silicide. Under annealing the film is transformed into Pd2Si islands standing on the SiC (1×1) surface. No extra-structure of C 1s is observed in the two cases; only an energy shift of about 0.25 eV is detected during the metal deposition, which is attributed to a change in the band bending. Further deposition of ∼100 A of Pd on this annealed surface gives an epitaxial Pd(111) film, despite a lattice mismatch of more than 10% between the metal and the semiconductor. The film is disrupted after annealing at 600–800 °C. The combination of XPS, AFM and GIXRD analyses indicates that the film annealed at 800 °C is discontinuous and formed of sharp epitaxial Pd2Si islands and graphite which probably surrounds the islands.

Direct and inverse photoemission in the U.V. range and soft X-ray emission spectra (SiL 2,3 ) are presented for silicon di-oxides. These measurements concern amorphous (a-SiO 2 ) and cristalline (quartz) dioxides. These results allow an investigation of the electronic structure of these compounds around the Fermi level. Furthermore they show clearly that no Si3d electrons are present at the top of the valence band Resultats d'experiences de photoemission directe et inverse dans le domaine UV et d'emission de rayons X mous (SiL 2,3 ) sur SiO 2 amorphe et cristallise (quartz). Renseignements obtenus sur la structure electronique de part et d'autre du niveau de Fermi. Absence d'electrons 3d de Si au sommet de la bande de valence, en accord avec les calculs