ON THE RESTRUCTURED LAYER OF THE SI(111)ROOT-3X-ROOT-3-AG STRUCTURE STUDIES BY SCANNING TUNNELING MICROSCOPY

The restructuring of the square-root 3 X square-root 3 structure formed by Ag adsorption on the clean Si(111)7 X 7 surface is studied by scanning tunneling microscopy. After the deposition of Ag on the Si(111)7 X 7 surface at 130-degrees-C, the specimen is annealed at congruent-to 380-degrees-C to create the square-root 3 x square-root 3 structure. The position of the bright dots of the square-root 3 X square-root 3 structure in the STM images is confirmed to be at the H-3 site, which agrees with the previous STM work. The square-root 3 X square-root 3 structure formed on terraces is found to consist of a hole-island pair, which is a pair of areas of the square-root 3 X square-root 3 structure lying higher and lower than the 7 X 7 surface. The hole-island pair is formed due to the change in the number density of the Si atoms by the restructuring from the 7 X 7 structure to the square-root 3 X square-root 3 structure. The number density of the Si atoms in the square-root 3 X square-root 3 structure is determined to be 1 ML, assuming that the 7 X 7 structure has the DAS (dimer-adatom-stacking fault) structure.