REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION ANALYSIS OF THE SI(111)-(7X7) RECONSTRUCTION

Most of the techniques used to determine the structure of reconstructed surfaces are relatively insensitive to displacements perpendicular to the surface, especially those of subsurface atoms. Reflection high-energy electron diffraction (RHEED) is sensitive to these displacements. We have performed a dynamical simulation of RHEED intensities and show that for the Si(111)-7 X 7 reconstruction, the dimer-adatom stacking-fault model optimized by ab initio parallel computation has given more accurate atomic Positions than previous determinations by other approaches. This indicates that the relative intensities of reflections in a RHEED pattern contain important, sensitive surface structural information.