Regular defects along the domain boundaries of clean (111) 7 x 7 surfaces were observed by means of scanning tunnelling microscopy. Their atomic structures were considered with respect to the dimer-adatom stacking fault model. It was found that there were 3 important basic factors which determined the boundary structure. The most important factor was a strong interaction between dimers and adatoms. The next most important factor, in some cases, was the difference between the faulted half and unfaulted half. The third factor was the presence of other metastable triangle sub-unit structures, such as 5 x 5. Under certain conditions, the atoms along the domain boundary could adjust so as to form such structures.

Q.J.Gu, Z.L.Ma, N.Liu, X.Ge, W.B.Zhao, Z.Q.Xue, S.J.Pang, Z.Y.Hua: Surface Science, 1995, 327, 241-7