Study of the Si(111) "5 x 5"-Cu surface structure by X-ray diffraction andscanning tunneling microscopy

The quasi-"5x5" structure on the Cu/Si(111) surface was investigated by sur face X-ray diffraction that utilized anomalous X-ray scattering by Cu atoms in part and scanning tunneling microscopy (STM), The X-ray reflectivity cu rve along the 00 rod was analyzed in the absolute scale to determine not on ly the vertical heights of the atomic layers of Cu but also the coverage of Cu atoms. The average interatomic distance of Cu-Cu was estimated by the m easurement of the anomalous X-ray scattering. Clear STM topographs that are probably able to explain the origin of the "5x5" structure were taken. The topograph images also support the results of the X-ray diffraction.