RESTRUCTURING OF THE RECONSTRUCTED SI(111)7 X 7 SURFACE BY METAL(AU, AG) DEPOSITION

Restructuring epitaxy of Au and Ag on the Si(111)7 x 7 reconstructed surface has been studied by scanning tunneling microscopy (STM), which proceeds with hole-island pair creation of the square-root 3 x square-root 3 structure on the 7 x 7 surface. The hole-island pair, which is a pair of areas with the square-root 3 x square-root 3 structure lying higher and lower than the 7 x 7 surface, is found to be due to the change in the numb density of the Si atoms in the reconstructed Si surface layer. The ratio of the area of the hole to that of the island is almost same from one pair to the other. The Si atoms of the reconstructed surface layer of the island e supposed to be supplied from the surface layer forming the hole. Provided that the number density of the Si atoms in the 7 x 7 surface is 2.08 ML according to the dimer adatom stacking-fault (DAS) model, the result indicates that the number density of Si atoms in both square-root 3 x square-root 3 structure is 1 ML and that almost all the Si atoms which included in the initial 7 x 7 surface are preserved to create the hole-island pair. Such restructuring epitaxy results in roughness of the surface even if the initial surface is atomically flat.