Azimuthal dependence of the vibrational excitation in Si(111)-(2×1)

Abstract
The polarization of the surface vibrational excitation at 56 meV in Si(111)-(2×1) has been studied through high-resolution electron-energy-loss spectroscopy. By comparing the intensity of the loss peak for the incident plane normal and parallel to the chain direction of the surface reconstruction, we studied the surface anisotropy of the excitation. The experiments were also carried out at very low primary beam energies in order to avoid the masking effects of the kinematics. Comparing the results with the calculations performed with a model loss function, we obtained that both isotropic and anisotropic contributions are present in this loss feature.