Manipulation of atoms across a surface at room temperature

Abstract

Since the realization that the tips of scanning probe microscopes can interact with atoms at surfaces, there has been much interest in the possibility of building or modifying nanostructures or molecules directly from single atoms. Individual large molecules can be positioned on surfaces, and atoms can be transferred controllably between the sample and probe tip. The most complex structures are produced at cryogenic temperatures by sliding atoms across a surface to chosen sites. But there are problems in manipulating atoms laterally at higher temperatures - atoms that are sufficiently well bound to a surface to be stable at higher temperatures require a stronger tip interaction to be moved. This situation differs significantly from the idealized weakly interacting tips of scanning tunnelling or atomic force microscopes. Here we demonstrate that precise positioning of atoms on a copper surface is possible at room temperature. The triggering mechanism for the atomic motion unexpectedly depends on the tunnelling current density, rather than the electric field or proximity of tip and surface

A density functional study of Br on Cu() at low coverages

“…Most of the work on the construction of complex structures [7,8] has been performed at cryogenic temperatures using systems where the interaction between the adsorbate and the surface is weak, allowing the atoms to be manipulated with a weak tip-adatom interaction. Bromine on copper (100) is of great interest as a system where controlled room temperature nanomanipulation has been achieved [9]. An understanding of systems such as this one is essential if we are to suceed in "manufacturing" nanoscale devices.…”

“…The first is identification of the adsorption site. It is generally believed that Br on Cu(100) must occupy fourfold hollow sites as shown in figure 1, but a surprising result of the STM experiments is that the topographic features assigned to adsorbed bromine atoms appear in registry with the greyscale maxima of the STM images [9,10] (figure 2). This registry is preserved under a wide range of differing tip conditions which lead to imaging the bromine induced features as greyscale maxima, minima or Mexican hat sombreros [10].…”

Atom manipulation on an insulating surface at room temperature

“…In mechanical-induced manipulation, the attractive and repulsive interaction forces between the probe tip and the target object are used to drive the motion [16][17][18][19][20] . In contrast, in electron-induced manipulation the atom or molecule is excited by the inelastic tunnelling electron and hence they start to diffuse themselves [21][22][23][24] . In both modes, manipulation at RT requires a delicate balance between a high enough initial binding energy to the substrate to avoid desorption and a small enough diffusion barrier to be able to be influenced by the local probe tip.…”

Room-temperature-concerted switch made of a binary atom cluster

“…Extensive SPM studies have reported a variety of methods for single-atom/ molecule manipulation that are mediated by several tip-sample interactions 1,2,28,29 . We used a combined AFM/STM to fabricate and operate an atomic-scale switch at RT, which enables individual interactions during each manipulation process to be directly monitored.…”