Structures chimique et electronique de l'interface SiO 2-Si

Abstract

Photoelectron spectroscopies (XPS and UPS) and X-ray excited Auger spectroscopy are used to characterize the local atomic order and the electronic structure of the transition layer at the interface between thermally grown oxide films and a Si(111) substrate. High resolution Si KLL Auger spectra induced by Cr Kα X-rays are used to detect intermediate oxidation states of silicon which are characteristic of the chemical transition layer. A simple procedure is described, which permits expressing the experimental core level shifts in terms of chemical, relaxation and Fermi level shifts, from a combination of core level Auger and photoelectron energies. The photoelectron Si 2p shift from ∼3.5 eV to 4.1 eV is explained in terms of variation of relaxation energy. Data obtained from an analysis of the variations in core level binding energies, Auger energies and valence densities of states support an abrupt interface, with a 3–4 Å chemical transition layer, and a 15 Å SiO 2 layer where the properties are different from that of the bulk oxide.