MULTIPLE-SCATTERING CALCULATIONS OF GBMEED

A method for computing grazing-incidence backscattering medium energy (1-3 keV) electron diffraction (GBMEED) is presented. The technique wa s recently proposed as a structural tool exhibiting diffraction effect s resembling those of XPD. In GBMEED the intensity of quasielastically thermal diffuse scattering is measured at large scattering angles suc h that different atoms can be assumed to vibrate independently, and th us represent localized sources for diffuse scattering in the surface l ayers. The basis of the calculations is the multiple scattering theory of diffuse RHEED adopted to the medium energy case with a vibrating a tom as source of diffuse scattering. Calculated plots of the intensity versus azimuthal/polar exit angle for an In overlayer on Si(111) show the forward focusing effect along the source-scatterer direction (wel l known from XPD) and further fine structure.