Effective energy-loss functions for oxygen-adsorbed amorphous silicon surfaces

Effective energy-loss functions were derived for oxygen-adsorbed amorphous silicon surfaces from a reflection electron energy-loss spectroscopy analys is based on the extended Landau theory. This study has revealed that the in tensity of the surface-plasmon-loss peak for a clean surface decreases and its peak position shifts towards the lower-energy losses as oxygen exposure proceeds (less than or equal to 1000 L). To understand the above behavior of the surface-plasmon-loss peak, the distribution of the energy losses was calculated using the hydrodynamic model. The decrease and shift of the sur face-plasmon-loss peak has been described with considerable success by assu ming that the quasifree static electron density in the vicinity of the sili con surface decreases as oxygen adsorption proceeds owing to oxygen's high electron affinity. (C) 1999 American Institute of Physics. [S0021-8979(99)0 0908-1].