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For a set of fcc metals, our total energy calculations based on many body potentials show that activation barriers for lateral manipulation of an adatom at a step edge depend on the tip/substrate composition. Of the six homogeneous systems studied, manipulation on stepped Ag(111) showed the lowest energy barrier for adatom hopping toward the tip, a...
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... is calculated for each configuration of the system with the adatom placed at every point along a fine 10Å x 10Å grid consisting of 100 x 100 points, which covers part of the upper and lower terraces adjoining the step. The potential energy surface of the system was obtained from the total energy of the system for each of the 10 4 configurations (Fig. 2). From the calculated potential energy surface, the activation energies for the adatom to diffuse in various directions were then obtained. In the case of vertical manipulation, the adatom is constrained in the Z direction (normal to the surface). This prevents the adatom from falling back to the surface when it is raised in small ...
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... Many experimental and theoretical investigations have shown that the atomic manipulation is usually influenced by the details of the STM tip [18][19][20][21][22][23][24]. In our previous work [18], we have already revealed the dependence of the Co adatom extraction on tip composition and geometry structure in the VM process. ...
A successful atomic manipulation may be influenced by many factors such as bias voltage, tip structure and manipulation modes et al. Here, performing atomic-scale simulations with ab initio based many-body potentials, we have studied the vertical and lateral manipulation of a single Co adatom on metallic Cu surfaces using STM tips at zero bias voltage. A suitable scheme for manipulating the Co adatom on a Cu(554) surface is proposed. The optimum tip height for a successful lateral manipulation is determined and the reliability of the lateral manipulation of the adatom on the stepped surface is assessed.
... It is also of much interest to achieve the controllable fabrication of the nanoparticle and the modification of its configuration with the atomic level accuracy. A promising method is the single-atom manipulation using the scanning tunnelling microscope (STM) (Deshpande et al. 2007;Eigler and Schweizer 1990;Eigler et al. 1991;Ghosh et al. 2006;Li et al. 1998;Meyer et al. 1997;Song et al. 2009;Stroscio and Eigler 1991;Xie et al. 2008) or the atomic force microscope (AFM) (Sugimoto et al. 2008;Ternes et al. 2008), which has proven to be a powerful tool in the nanofabrication. This technique provides a bottom-up way to fabricate nanostructures, making it possible to design nanoparticles with the desirable properties. ...
... In qualitative agreement with our results, earlier theoretical work (Ghosh et al. 2006) also suggests that it tends to be more easier to extract vertically an atom from the step edge of the stepped Cu(111) surface than from the flat one using the pyramidal Cu trimer-apex tip, since the tip decreases more effectively the energy barrier of extracting a single atom for the stepped surface than for the flat one. In the former case, the neighbor atoms experience more displacements induced by the tip, which facilitates the extraction. ...
First-principles simulations show that at the step edge of the stepped Al(001) and (110) surfaces and at the edge of the small
supported nanoparticles like the dimer, trimer, and tetramer, single Al atoms can be extracted and repositioned using the
Cu trimer-apex tip and the Pt tip of a Al apex, while a more weakly adsorbed single Al adatom on the plane terrace of the
flat surface or of the nanocluster cannot be vertically picked up by these two tips. This result suggests in principle a non-electrically
assisted method of fabricating and modifying metal nanoparticles at the atomic scale using the vertical single-atom manipulation.
As an illustration, a pyramidal nanocluster of five Al atoms is assembled on the Al(001) surface in an atom-by-atom way with
the Cu trimer-apex tip, moreover, it can be modified to be two-dimensional in shape.
KeywordsMetal nanoparticle–Aluminum–Platinum–Metal surface–Single-atom manipulation–Tip–Synthesis–Nanomanufacturing
... The lowering of the barrier is also found to depend on the tip composition. A Cu tip is more effective in lowering the barrier of a Pt atom on a Pt surface as compared to a Pt tip [25]. Bouju et al [26] have found that the dragging mechanism for a Xe adsorbate on a Cu(110) surface depends on tip geometry. ...
Atomic-scale simulations are performed to study the vertical manipulation of single Co adatoms on a Cu(001) surface using a scanning tunneling microscopy (STM) tip. Cu and Co tips with different geometries are investigated. Our results demonstrate that the details of the tip significantly affect the manipulation of the Co adatom. The differences in the manipulation of the Co adatom using different tips and the dependence on tip geometry are revealed. The possibilities and mechanism of extracting single adatoms on metal surfaces with a STM tip at zero bias voltage are explored.
In this paper, the electronic properties, the adhesive energy, and the interface energy of the MAX phase Ti2SnC(0001)/Ag(111) interface are systematically investigated using first principles based on density functional theory. Four different terminations of Ti2SnC(0001) are considered, and 16 different Ti2SnC(0001)/Ag(111) interface configurations are obtained by varying the stacking positions of the atoms. After calculating the electronic structure, adhesion work, and interface energy of these interface model interfaces with the same terminal but different atomic positions, it is found that the interface of the same terminal has a very limited effect on the interface bonding of the interface model by changing the stacking order of the interface atomic layer. By comparing the adhesion work and interface energy of 16 interface models, it is found that the HCP2 configuration of C‐Ti2SnC(0001)/Ag(111)interface structure has the highest adhesion work and the lowest interface energy. The larger the adhesion work is, the stronger the bonding between the interface atoms is. Meanwhile, the smaller the interface energy (positive value) is, the more stable the interface is. By calculating the electronic structure of the interface, the accuracy of the above results is further verified after analyzing the partial density of states (PDOS) and charge density difference of the interface.
We study the physics of atomic manipulation of CO on a Cu(111) surface by combined scanning tunneling microscopy and atomic force microscopy at liquid helium temperatures. In atomic manipulation, an adsorbed atom or molecule is arranged on the surface using the interaction of the adsorbate with substrate and tip. While previous experiments are consistent with a linear superposition model of tip and substrate forces, we find that the force threshold depends on the force field of the tip. Here, we use carbon monoxide front atom identification (COFI) to characterize the tip's force field. Tips that show COFI profiles with an attractive center can manipulate CO in any direction while tips with a repulsive center can only manipulate in certain directions. The force thresholds are independent of bias voltage in a range from 1 to 10 mV and independent of temperature in a range of 4.5 to 7.5 K.
Single atom manipulations are studied on Ag, Pt, and Cu fcc(001) surfaces at elevated temperature with molecular statics and dynamics methods. Owing to the strong adatom-surface interactions, although the energy barrier along the manipulation direction cannot be eliminated by the tip, the effect of which on the energy landscape and then the dynamics of adatom could be large, including not only the diffusion direction like on Pt(001) but also the dominant diffusion mechanism on Ag(001) surface. When the tip height and position are set properly, the adatom migrating to the tip will become almost the unique diffusion process, which suggests a novel way to control atoms with fascinating reliability in spite of the stochastic disturbance at elevated temperature.
Using molecular statistics simulations based on the embedded atom method potential, we investigate the reliability of the lateral manipulation of single Pt adatom on Pt(111) surface with a single-atom tip for different tip heights (tip-surface distance) and tip orientations. In the higher tip-height range, tip orientation has little influence on the reliability of the manipulation, and there is an optimal manipulation reliability in this range. In the lower tip-height range the reliability is sensitive to the tip orientation, suggesting that we can obtain a better manipulation reliability with a proper tip orientation. These results can also be extended to the lateral manipulation of Pd adatom on Pd(111) surface.
With a triple-apex tip, we investigate theoretically the vertical manipulation of single Pt adatom on the Pt(111) surface. The adatom adsorbed on the fcc site of the flat Pt(111) surface can be transferred vertically to the tip by adjusting the tip height properly. Moreover, based on the strong vertical trapping ability and the relatively weak lateral trapping ability of the tip, we propose a simple method to realize a reversible vertical manipulation of the Pt adatom from the highly coordinated sites, the kink and the step sites, of the stepped Pt(111) surface. All the vertical manipulations are completed using only the atomic force between the tip and the adatom, without the electric field.
Scanning tunneling microscopy (STM) has greatly contributed to the field of surface science over the past two decades. Today, the STM is a powerful instrument contributing to the study of emerging research directions in nanoscience. With a suitable choice of STM manipulations combined with tunneling spectroscopy and imaging, experiments can be tailored to investigate electronic, structural, and mechanical properties specific to atoms, molecules, and nanosystems. In this article, the basic STM manipulation schemes are explained and some examples of STM manipulation experiments related to the atomistic constructions and mono-molecular devices are described.
