Optical absorption in ultrathin silicon oxide films near the SiO2/Si interface

The optical absorption in ultrathin silicon oxide films was studied by measuring their reflectance spectra in the vacuum ultraviolet. By applying a modified Kramers-Kronig analysis, with multiple reflections at the boundaries of the film taken into account, depth profiling was performed of the optical absorption in the oxide films near the SiO2/Si interface below the fundamental absorption edge of fused quartz. The structural imperfections contributing to this optical absorption were found to arise partly from Si-Si bonds localized within a distance of 1.4 nm from the interface in the oxide films.