Tip-induced adatom extraction and cluster manipulation

Abstract

We present results for tip-induced extraction of a Cu adatom from Cu mound on Cu(111), and compare the characteristics to that for a similar Ag system. Molecular-dynamics and molecular static simulations were carried out using interaction potentials from the embedded atom method. Molecular-dynamics simulations revealed differences in the modes of extraction for the cases of Ag and Cu systems and their dependence on tip geometry. For the case of a sharp Ag tip, the extraction of a Ag adatom occurs via the pulling mode, while with a blunt Ag tip, the extraction is more complex involving a two-step motion. On the other hand, the relatively stronger Cu-Cu interaction leads to a sliding and/or dragging mode in which the whole three-dimensional cluster is dragged followed by the extraction of the adatom from the cluster. Molecular static simulations provide a detailed analysis of the changes in the energy landscape in the presence of the tip, resulting in a substantial decrease of the energy barrier for an adatom to descend from the mound.