High energy transmission electron diffraction and imaging studies of the silicon (111) 7 × 7 surface structure

Kilovolt electron scattering experiments in the transmission geometry offer certain advantages for surface structure analysis over more traditional techniques. These include the absence of electron exchange effects, the ability to analyze submicron regions, their compatibility with imaging (for the study of chemically important inhomogeneities) and the usefulness of the kinematic approximation for surface superlattice reflections. An experimental 100 kV transmission electron diffraction pattern from the silicon [111] 7 × 7 structure is analyzed and compared with the diffracted intensities expected from two recent models for the 7 × 7 adlayer. Shuffle and glide termination effects are discussed. Thousand-beam dynamical calculations of atomic resolution transmission electron images of the surface superlattice are used to show the high sensitivity of these to charge transfer effects, and the imaging conditions needed to maximize this sensitivity are determined.