Modification of Si(100) Substrate Bonding by Adsorbed Ge or Si Dimer Islands

High-resolution scanning tunneling microscopy studies of the Si(100)-( 2{times}1) surface show a heretofore unrecognized distortion of the substrate structure when islands form during the initial stage of growth of either Si or Ge. The distortion, reflecting the influence of strain, extends at least three dimers away from the adsorption sites. We present a realistic structural model. {copyright} {ital 1998} {ital The American Physical Society}