INVESTIGATION OF ATOM-RESOLVED DOMAIN BOUNDARIES ON SI(111)7X7 SURFACES BY SCANNING-TUNNELING-MICROSCOPY

Several regular defects along domain boundaries of clean Si(111)7 x 7 surfaces have been observed with scanning tunneling microscopy (STM), Combined with the dimer-adatom-stacking fault (DAS) model, their detailed atom structures are discussed. We have found three important elementary factors that determine the boundary structure. The most important factor is the strong interaction between dimer and adatom. The next, in some cases, is the difference between faulted half and unfaulted half. The third factor are other metastable triangle subunit structures (e.g. 5 x 5, etc.). Under certain conditions the atoms along the domain boundary will adjust to form such structures.