ANALYSIS OF LOW-ENERGY ELECTRON-DIFFRACTION PATTERNS FROM SIMPLE OVERLAYER SURFACE STRUCTURES .2.

The role of multiple diffraction and overlayer distortion in low-energy electron diffraction from simple overlayer structures is discussed. In a development of the multiple-diffraction approach from scattering theory, the contribution of evanescent waves, scattered from the substrate or overlayer, to the intensity of multiple-diffraction beams is included. This generalized multiple-diffraction treatment is applied to a simple Ag-covered Cu(100) surface structure and shown to be adequate for explaining salient features of the observed pattern. The contribution of overlayer distortion to the pattern from the same structure is also considered and shown to be significant at high energy. It is concluded that in the very low energy range, multiple-diffraction effects are very likely dominant in determining pattern intensity.