Soft-x-ray emission and inelastic electron-scattering study of the electronic excitations in amorphous and crystalline silicon dioxide

The valence-band electronic structures of amorphous and crystalline SiO₂ are examined with soft-x-ray emission spectroscopy. In addition, the absorption spectra of a-SiO₂ obtained by inelastic electron scattering (IES) near the interband threshold and Si L₂₃ threshold regions are presented. Simple models used to describe the absorption in these spectral regions give consistent values for the size of the band gap of SiO₂. An empirical model based on these results is presented to explain the positions of peaks in the ultraviolet optical spectrum and the IES valence excitation spectrum of SiO₂. The Si 2p core exciton observed in both x-ray emission and absorption spectra is discussed.