Examination of the cu/si(111) 5×5 structure by scanning tunneling microscopy

The incommensurate 5×5 Cu/Si(111) structure has been examined by scanning tunneling microscopy. Images show that the surface structure is not well described as a hexagonal copper layer modulated at the Si(111) periodicity. Rather, the surface breaks up into 5×5 subunits which pack at spacings varying from 5 to 7 lattice constants, implying that substrate-adsorbate interactions dominate lateral interactions within the Cu adlayer. © 1988 The American Physical Society.