(A) study on the Mg adsorption on the Si(111) surface by LEED and STM

Abstract

The adsorption of Mg on the Si(111) 7×7 surface has been studied using low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). The evolution of the adsorption behavior of Mg with increasing coverage has been investigated by evaporating the Mg atoms on the Si(111) 7×7 surface at both room temperature and elevated temperature. At the very early stages of Mg adsorption, the 7×7 units of the Si(111) surface remain intact. At room temperature Mg adsorption, three different adsorption features are shown, but the number of adsorption features is changed by annealing. As the Mg coverage at room temperature increases, the Si(111) 7×7 LEED pattern becomes weaker and a new $\frac{2}{3} \sqrt{3}×\frac{2}{3} \sqrt3R30℃$ LEED pattern evolves. In STM images, it has been found that the triangular network of the 7×7 units remain undisrupted until the whole surface is covered by the Mg atoms. Upon slight annealing, the 7×7 units are disrupted and patches of 3×2 atomic row structures are formed on the surface, which is shown to be the 3×1 pattern in LEED. The Mg evaporation on the Si(111) 7×7 surface at elevated temperature also results in the 7×7 LEED pattern and the row structure STM image