RESTRUCTURING PROCESS OF THE SI(111) SURFACE UPON AG DEPOSITION STUDIED BY IN-SITU HIGH-TEMPERATURE SCANNING-TUNNELING-MICROSCOPY

Restructuring processes of the Si(111) surface from the 7X7 to the squ are-root 3 X square-root 3 structure upon the deposition of Ag has bee n observed by a high-temperature in situ STM method. Although the squa re-root 3 X square-root 3 structure is formed at substrate temperature s above 240-degrees-C, Ag islands do not have the square-root 3 X squa re-root 3 structure at the initial stage of the condensation. The rest ructuring is found to occur after the Ag island has grown larger than the critical size, which is four times as large as the half unit cell of the 7X7 structure. The restructuring starts from the edges of such Ag islands and the area of the square-root 3 X square-root 3 structure expands gradually as they grow. The hole-island pairs are formed so a s to conserve the number of Si atoms underneath each Ag island.