Electron inelastic interactions with overlayer systems

An overlayer system composed of a thin film on the top of a semi-infinite s ubstrate was studied in this work for electron inelastic interactions. Anal ytical expressions for the depth-dependent inelastic differential and integ ral inverse mean free paths were derived for both incident and escaping ele ctrons. The interface (film-substrate) effect and the surface (vacuum-film) effect were analyzed by comparing the results of an overlayer system and a semi-infinite system. It was found that the interface effect extended to s everal angstroms on both sides of the interface for a 500 eV electron incid ent into or escaping from the vacuum-SiO2-Si and the vacuum-Au-Ni systems. An application of the spatial-varying inelastic differential inverse mean f ree paths was made by Monte Carlo simulations of the electron elastic backs cattering from an overlayer system. Good agreement was found between result s calculated presently and data measured experimentally on the elastic refl ection coefficient. (C) 1999 American Institute of Physics. [S0021-8979(99) 00712-4].