A theory of low-energy-electron diffraction for simplifying overlayer calculations

Abstract

The effect of the deposition of an overlayer on low-energy-electron- diffraction patterns is described by a Green's-function method which calculates the Green's function associated with the surface before the deposition of an overlayer. The theory treats the clean-surface reflection coefficients as input information. A muffin-tin-potential model is assumed for the two-dimensionally periodic overlayer. The exact reflection coefficient of an elastically scattered beam from the overlayer-substrate system is expressed in terms of structure constants and phase shifts of the adsorbate, as well as the reflection coefficients of diffracted beams from the clean substrate. With known clean- surface reflection coefficients, the overlayer problem is similar to that of a monolayer crystal, the structure constants and the phase shifts of the adsorbate only are necessary to be calculated. Thus this theory offers a simpler way in dealing with complicated overlayer low-energy-electron-diffraction problems. (AIP)