Core and valence electron excitations of amorphous silicon oxide and silicon nitride studied by low energy electron loss spectroscopy

Abstract

Valence and core electron excitations were measured for thermal SiO 2 films and chemical-vapour-deposited Si 3N 4 films using low energy electron loss spectroscopy (ELS). A reasonable interpretation of the spectra can be obtained using electron energy level diagrams derived from optical and X-ray experiments and from theoretical calculations using literature values. The electron levels of these amorphous materials can then be described by localized molecular states. The ELS spectra show the formation of basic [SiO 4] and [SiN 4] tetrahedra and the existence of Si-Si bonds in mixed tetrahedra, suggesting a deviation from ideal stoichiometry and the presence of broken Si-O and Si-N bonds. Auger spectra have also been measured for elemental silicon, for SiO 2 and for Si 3N 4 and are discussed in terms of chemical shifts and line shape.