Surface Vibrations of Silicon Detected by Low-Energy Electron Spectroscopy

The energy loss of 5-eV electrons reflected from clean and from oxidized (111) silicon surfaces has been investigated. A surface phonon with ω≈55 meV, k≈0 is found at the clean surface. After exposure to {}10^-5 Torr min oxygen, three energy losses at 48, 90, and 125 meV occur. Models for the electron-phonon interaction, the nature of the surface phonon, and the structure of the oxidized surface are proposed.