The Si L2,3 edge shifts upwards in energy from ~99 eV for c-Si to ~103 ev for Si3N4 to 106 for SiO2. This reflects both an increasing optical gap, and an increased binding energy as the formal valence increase from 0 to 4+. The c-Si can be interpreted qualitatively in terms of its ground state DOS, but the SiO2 spectra is dominated by excitonic peaks at 106, 108 eV.
By: Aycan Yurtsever
Microscope: VG HB 501UX STEM
Energy Resolution: 0.5eV