STRUCTURE ANALYSIS OF${\rm Si}(111)(\sqrt{3}\times\sqrt{3}$)–AlBY ENERGY-FILTERED RHEED

Rocking curves of energy-filtered reflection high-energy electron diffraction (EF-RHEED) intensities from the Si(111)($\sqrt{3} \times \sqrt{3}$)–Al surface have been measured. The EF-RHEED apparatus is a recently developed one, equipped with a retarding field analyzer to exclude inelastic scattering component from an entire RHEED pattern. The energy-filtered rocking curves measured atEloss=90eV and 0 eV are compared. It is found that when theElossvalue comes close to 0 eV the relative intensities of reflection beams become remarkably weak at the lower angle side. Three structure models, which have already been presented as theT4model, and additionally two simple rigid sphere models, are examined by dynamical calculations of RHEED. It is found that Hanadaet al.'s structure model is the most favorable one among them. In the analysis of zero-loss rocking curves, especially, an extended imaginary potential distribution into the vacuum is tentatively used to express the absorption due to surface plasmon loss and fairly good agreements between the calculated and experimental rocking curves are obtained.