Scanning tunnelling microscopy was used to study structural defects on hydrogenated (111) 1 x 1 surfaces which had been prepared by means of the  in situ  H exposure of (111) 7 x 7 surfaces at high temperatures. These defects could be divided into 4 categories. These were: point-like defects, holes in the first bulk bilayer, islands, and stacking fault regions. The 2 most frequently occurring point-like defects were adatom trihydrides and top-layer atoms with a missing H atom. The islands which were observed on the 1 x 1 hydrogenated surfaces were single-layer linear islands and bilayer linear and triangular islands. Three distinct types of island edges were identified, and structural models were proposed for each type. These models, which involved various arrangements of tilted monohydride edge species, were also applicable to step edges on the surfaces which were created. The stacking fault regions, triangular in shape, were found to have a double periodicity along the borders. The latter was explained in terms of a dimerization of the surrounding second-layer atoms.

F.Owman, P.Mårtensson: Surface Science, 1995, 324, 211-25