DYNAMICAL ANALYSIS OF A RHEED PATTERN FROM THE SI(111)-7X7 SURFACE

The multislice formalism of Cowley and Moodie [Acta Crystallogr. 10 (1957) 609] with a recently developed edge-patching method has been applied to the analysis of an experimental RHEED (reflection high energy electron diffraction) pattern from the Si(111)-7 x 7 surface. Several data sets of atomic coordinates for the Si(111)-7 x 7 reconstruction, optimized by different approaches, have been evaluated based upon comparison of visually estimated intensity ordering between the observed and calculated patterns. The results show that compared to other data sets, the coordinates optimized by ab initio-parallel computation appear closer to the true structure, so far as the RHEED in the current scheme can judge. The analysis also shows that the intensities of a RHEED pattern taken from the surface are highly surface sensitive. The surface sensitivity extends to the whole selvage region of interest with a depth of approximately 10 angstrom. The correlation between mean inner potential V0 and the angle of incidence theta has also been investigated. This indicates that if the angle of incidence is measured with errors less than +/-0.05-degrees for this specific case, V0 can be determined with the accuracy of approximately +/-10%, and vice versa.