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

Most of the techniques used to determine the structure of reconstructe d surfaces are relatively insensitive to displacements perpendicular t o the surface, especially those of subsurface atoms. Reflection high-e nergy electron diffraction (RHEED) is sensitive to these displacements . We have performed a dynamical simulation of RHEED intensities and sh ow that for the Si(111)-7 X 7 reconstruction, the dimer-adatom stackin g-fault model optimized by ab initio parallel computation has given mo re accurate atomic Positions than previous determinations by other app roaches. This indicates that the relative intensities of reflections i n a RHEED pattern contain important, sensitive surface structural info rmation.