Evidence of SiOx suboxides at Ar ion etched silica surfaces

X-ray photoelectron spectroscopy (XPS), Auger spectroscopy, and synchrotron radiation (SR) photoemission are used for studying composition changes induced by 1--8 keV Ar ions on silica surfaces. When recorded at normal electron emission, both XPS and Auger spectra show that SiOx phases (0<x<2) form for Ar energies higher than 2 keV. The presence of these species is also disclosed by the silicon Auger parameters. The 0/Si atomic ratio, calculated by quantitative XPS analysis, drops well below two for impact energies ≥5 keV. SR photoemission and angular dependent XPS results, obtained at depth resolutions in the range 4--10 A, show that photoemission techniques possess a chemical capability for discriminating between SiOx suboxides and silica, which is comparable with that achievable by Auger Si LVV spectra