Core-Electron Excitation Spectra of Si, SiO, and SiO2

The excitation spectra of Si(2p) and O(1s) core electrons, measured by low-energy electron-loss spectroscopy, yield detailed information on the excited states of Si, SiO, and SiO2. The presence of an empty surface state near the top of the valence band on clean Si is directly demonstrated for the first time. For SiO2, the results indicate the presence of five empty states in the conduction band. © 1975 The American Physical Society.