Dimer formation and surface alloying: A STM study of lead on Cu(211)

We present a STM investigation of Pb adsorption on the Cu(211) surface in the temperature range between 30 K and room temperature. We observe three different kinds of ordered 1D Pb and Pb-Cu chains (nanowires) located at the intrinsic step edges of the Cu(211) surface. On room temperature prepared samples, Pb is found to be incorporated into the step edges of the (211) surface. The first ordered structure consists of Cu-Pb chains at the step edges (p(2 x disorder)) and is followed with increasing coverage by a close packed row of Pb-atoms (p(4 x disorder)). Preparation at low temperature yields Pb-dimers, and the first ordered structure is a row of Pb-dimers at the step edge (p(3 x disorder)) followed with increased coverage by a structure as described above. By systematic manipulation with the tunneling tip, we could get additional insight into the structural elements of the Pb-Cu layer on the atomic scale. Furthermore, by measuring the threshold resistance to detach atoms from different ad-sites, we can approximately determine the binding energy and gain some insight into the thermodynamical parameters involved.