Reliable lateral and vertical manipulations of a single Cu adatom on a Cu(111) surfacewith multi-atom apex tip: semiempirical and first-principles simulations

Abstract

We study the reliability of the lateral manipulation of a single Cu adatom on a Cu(111)surface with single-atom, dimer and trimer apex tips using both semiempirical andfirst-principles simulations. The dependence of the manipulation reliability on tip height isinvestigated. For the single-atom apex tip the manipulation reliability increasesmonotonically with decreasing tip height. For the dimer and trimer apex tips themanipulation reliability is greatly improved compared to that for the single-atom apex tipover a certain tip-height range. Two kinds of mechanism are found responsible for thisimprovement. One is the so-called enhanced interaction mechanism in which the lateraltip–adatom interaction in the manipulation direction is improved. The other is thesuspended atom mechanism in which the relative lateral trapping ability of the tip isimproved due to the strong vertical attraction of the tip on the adatom. Both mechanismsoccur in the manipulations with the trimer apex tip, while in those with the dimerapex tip only the former is effective. Moreover, we present a method to realizereversible vertical manipulation of a single atom on a Cu(111) surface with thetrimer apex tip, based on its strong vertical and lateral attraction on the adatom.