Scanning-tunneling-microscopy images of Ge adsorbed on an As-covered Si(001) surface

We present scanning-tunneling-microscopy images that support the single-dimer exchange mechanism proposed for surfactant-mediated epitaxial growth of Ge on the Si(001) surface [Phys. Rev. Lett. 72, 3190 (1994)]. Unusual features of the calculated images corresponding to the (meta)stable geometries during the exchange process are bright spots between the dimer rows and their variation depending on the bias voltage. The experimental image also shows the bright spots between the dimer rows.