Embedded structure of silicon monoxide in SiO2 films

The structure of SiOx (x = 1.94) films has been investigated using both X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The SiOx films were deposited by vacuum evaporation. XPS spectra show that SiO1.94 films are composed of silicon suboxides and the SiO2 matrix. Silicon clusters appeared only negligibly in the films in the XPS spectra. Si3O+ ion species were found in the TOF-SIMS spectra with strong intensity. These results reveal the structure of the films to be silicon monoxide embedded in SiO2, and this structure most likely exists as a predominant form of Si3O4. The existence of Si-Si structures in the SiO2 matrix will give rise to dense parts in loose glass networks.