Structure of the modified surface layer formed by ion bombardment of SiO 2 films

Abstract

The structure of thin (7–809 nm) SiO 2 films subjected to a bombardment of 40Ar ions of 2.7 keV is studied using infrared spectroscopy with computer analysis of the spectral shape, multiple-angle spectral ellipsometry and Auger spectroscopy. The formation of a surface modified layer (∼ 19 nm thick) is observed, which possesses the properties substantially different from those of the initial SiO 2 (a pronounced absorption in the visible and nearest ultraviolet spectral range, specific shape of the vibrational spectrum, the peak at ∼ 11 eV in the Auger electron spectrum). Deconvolution of the silicon-oxygen stretching band into gaussian profiles made it possible to separate new elementary bands (with peak positions of ∼ 1012 and ∼ 1038 cm −1), which being absent in the SiO 2 spectrum are the principal components of the SiO x absorption band. A model of the modified layer structure is developed in which a combination of SiO y Si 4− y ( O ⩽ y ⩽ 4) cluster is considered; the contribution of each cluster var ies in depth.