Geometrical correction to plasmon effects in energy-filtered RHEED spectra

We investigate a recent experimental study of Si(111)7x7 using energy-filtered reflection high energy electron diffraction (EF-RHEED). Using a simple single scattering model incorporating both surface and bulk plasmons we consider the relative intensities of the diffraction peaks of the corresponding specular and 11 rocking curves as a function of energy-loss of the reflected electrons. At its simplest level, the model predicts the inelastic EF-RHEED rocking curves will scale with their elastic counterpart approximately as the inverse of the incident angle in the specular case, and as a sum of the inverses of the incident angle and reflecting angle in the non-specular case. This is found to work remarkably well for Si(111)7 x 7 for small energy losses (<20-30 eV), becoming progressively worse at higher energy-loss windows due to the inclusion of multiple plasmon creation. The exceptions to this are those specular and non-specular diffraction peaks that satisfy the emergence condition of higher-order beams. In these cases, the inelastic diffraction peaks concur more closely with their elastic counterparts, demonstrating a dominant coupling between these modes. (C) 1997 Elsevier Science B.V.