A STUDY OF SI(111)5 X 2-AU STRUCTURES BY LI ADSORPTION AND THEIR COADSORBED SUPERSTRUCTURES

Changes of the Si(111)5 × 2-Au surface structure upon Li adsorption were investigated by RHEED. The reciprocal lattice of the 5 × 2-Au structure consists of 1 5 order spots and 1 2 order streaks. Continuing the adsorption of Li on the 5 × 2-Au structure at room temperature, the 1 2 order streaks split at first into superlattice spots, changed their positions, and finally disappeared, whereas the 1 5 order spots survived. These facts suggest that the origins of the 1 5 order spots and the 1 2 order streaks are differe the atoms of the structure producing the 1 2 order streaks are movable at room temperature upon Li adsorption. The origin of the 1 2 order streaks was inferred to be displacement of loosely bound Au atoms. Including the results of the analysis of the RHEED intensity, a new model for the Si(111)5 × 2-Au was proposed. Besides, some new superstructures of coadsorption systems such as Si(lll)2√3 × 2√3-(Au, Li), Si(111)√3 × √3-(Au, Li) and Si(111)8 × 1-(Au, Li) have been found for the first time. © 1990.