Surface modifications induced by adsorbates at low coverage: A scanning tunneling microscopy study of the Ni/Si(111) 19 surface

Scanning tunneling microscope images of the 19 reconstruction of Ni/Si(111) are shown to rule out existing models for this surface. A new model, based on Si adatom stabilization and sixfold-coordinated Ni sites, is shown to give excellent agreement with the images and to explain the origin of the unit-cell geometry and some surface defects. The results demonstrate that nickel atoms, through Si adatom bonding, the strong effects on the bonding of first-, second-, and third-nearest-neighbor Si surface atoms. This realization provides important insight into the mechanism whereby very small quantities of nickel on the Si(111) surface completely alter the surface structure. © 1987 The American Physical Society.