Reliable Lateral Manipulation of Single Adatom on Metal fcc（lll） Surfaces with a Single-Atom Tip

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 P d （111） surface.     

First-principles study of Ar adsorptions on the （111） surfaces of Pd, Pt, Cu, and Rh

In the present paper we give a detailed report on the results of our first-principles investigations of Ar adsorptions at the four high symmetry sites on M （111） （M =Pd, Pt, Cu, and Rh） surfaces. Our studies indicate that the most stable adsorption sites of Ar on Pd （111） and Pt （111） surfaces are found to be the fcc-hollow sites. However, for Ar adsorptions on Cu （111） and Rh （111） surfaces, the most favorable site is the on-top site. The density of states （DOS） is analyzed for Ar adsorption on M （111） surfaces, and it is concluded that the adsorption behavior is dominated by the interaction between 3s, 3p orbits of Ar atoms and the d orbit of the base metal atoms.     

First-principle study of Mg adsorption on Si（111） surfaces

We have carried out first-principle calculations of Mg adsorption on Si(111) surfaces. Different adsorption sites and coverage effects have been considered. We found that the threefold hollow adsorption is energy-favoured in each coverage considered, while for the clean Si(111) surface of metallic feature, we found that 0.25 and 0.5 ML Mg adsorption leads to a semiconducting surface. The results for the electronic behaviour suggest a polarized covalent bonding between the Mg adatom and Si(111) surface.     

Influence of Pb adatom on adsorption of oxygen molecules on Pb(111) surface: a first-principles study

Using first-principles calculations, we systematically study the influence of Pb adatom on the adsorption and the dissociation of oxygen molecules on Pb(111) surface, to explore the effect of a point defect on the oxidation of the Pb(111) surface. We find that when an oxygen molecule is adsorbed near an adatom on the Pb surface, the molecule will be dissociated without any obvious barriers, and the dissociated O atoms bond with both the adatom and the surface Pb atoms. The adsorption energy in this situation is much larger than that on a clean Pb surface. Besides, for an adsorbed oxygen molecule on a clean Pb surface, a diffusing Pb adatom can also change its adsorption state and enlarge the adsorption energy for O, but it does not make the oxygen molecule dissociated. And in this situation, there is a molecule-like PbO2 cluster formed on the Pb surface.     

First-Principles Calculations of Atomic and Electronic Properties of T1 and In on Si（111）

The atomic and electronic structures of T1 and In on Si（111） surfaces are investigated using the firstprinciples total energy calculations. Total energy optimizations show that the energetically favored structure is 1/3 ML T1 adsorbed at the T4 sites on Si（111） surfaces. The adsorption energy difference of one T1 adatom between （√3 × √3） and （1 × 1） is less than that of each In adatom. The DOS indicates that TI 6p and Si 3p electrons play a very important role in the formation of the surface states. It is concluded that the bonding of TI adatoms on Si（111） surfaces is mainly polar covalent, which is weaker than that of In on Si（111）. So T1 atom is more easy to be migrated than In atom in the same external electric field and the structures of T1 on Si（111） is prone to switch between （√3 × √3） and （1 × 1）.     

Combined Effect of Surface Tension, Gravity and van der Waals Force Induced by a Non-Contact Probe Tip on the Shape of Liquid Surface

Aiming at understanding how a liquid film on a substrate affects the atomic force microscopic image in experiments, we present an analytical representation of the shape of liquid surface under van der Waals interactionin duced by a non-contact probe tip. The analytical expression shows good consistence with the corresponding numerical results. According to the expression, we find that the vertical scale of the liquid dome is mainly gov-rned by a combination of van der Waals force, surface tension and probe tip radius, and is weekly related to gravity. However, its horizontal extension is determined by the capillary length.     

Material transport in dip-pen nanolithography

Dip-pen na.nolithography （DPN） is a useful method for directly printing materials on surfaces with sub-50nm resolution. Because it, involves the physical transport of materials from a scanning probe tip to a surface and the subsequent chemical interaction of that material with the surface, there are many factors to consider when attempting to understand DPN. In this review, we overview the physical and chemical processes that are known to play a role in DPN, Through a detailed review of the literature, we classify inks into three general categories based on their transport properties, and highlight the myriad ways that. DPN can be used to perform chemistry at the tip of a scanning probe.     

A density-functional theory investigation on desorption of O2 on Sn（111） and its comparison with initial oxidation on the X（111） （X=Si,Ge, Sn,Pb） surfaces

<正>The first-principles calculations are performed to investigate the adsorption of O₂ molecules on an Sn（111） 2×2 surface.The chemisorbed adsorption precursor states for O₂ are identified to be along the parallel and vertical channels, and the surface reconstructions of Sn（lll） induced by oxygen adsorption are studied.Based on this,the adsorption behaviours of O₂ on X（111）（X=Si,Ge,Sn,Pb） surfaces are analysed,and the most stable adsorption channels of O₂ on X（111）（X=Si,Ge,Sn,Pb） are identified.The surface reconstructions and electron distributions along the most stable adsorption channels are discussed and compared.The results show that the O₂ adsorption ability declines gradually and the amount of charge transferred decreases with the enhancement of metallicity.     

Single atomic manipulation and writing with scanning tunnelling microscopy at low temperatures

In the work reported in this paper,we have used a low-temperature scanning tunnelling microscope (LT-STM) system to manipulate accurately single atoms.We show how we can use a LT-STM to image and modify a bulk Ag(111) surface and manipulate Ag atoms from substrate and evaporated adsorbates on Ag(111) substrates.We present a synergistic combination of SM-induced modification and ordered arrays of nanometre-scale structures.In particular,we demonstrate the ability to modify Ag atomic nanometre structures on the Ag(111) substrate,and some English letters and a Chinese character can be written by single Ag atoms coming from the substrate and evaporated adsorbates on Ag(111),In this way ,we supply an effective basis to explore the fundamental physical properties of a nanometre structure and to develop nanotechnology with a bottom-up approach,     

Manipulation and control of a single molecular rotor on Au (111) surface

Three different methods are used to manipulate and control phthalocyanine based single molecular rotors on Au (111) surface: (1) changing the molecular structure to alter the rotation potential; (2) using the tunnelling current of the scanning tunnelling microscope (STM) to change the thermal equilibrium of the molecular rotor; (3) artificial manipulation of the molecular rotor to switch the rotation on or off by an STM tip. Furthermore, a molecular `gear wheel' is successfully achieved with two neighbouring molecules.     

Vertical manipulation of native adatoms on the InAs(111)A surface

We achieved the repositioning of native In adatoms on the polar III-V semiconductor surface InAs(111)A-(2?×?2) with atomic precision in a scanning tunnelling microscope (STM) operated at 5?K. The repositioning is performed by vertical manipulation, i.e., a reversible transfer of an individual adatom between the surface and the STM tip. Surface-to-tip transfer is achieved by a stepwise vibrational excitation of the adsorbate-surface bond via inelastic electron tunnelling assisted by the tip-induced electric field. In contrast, tip-to-surface back-transfer occurs upon tip-surface point contact formation governed by short-range adhesive forces between the surface and the In atom located at the tip apex. In addition, we found that carrier transport through the point contact is not of ballistic nature but is due to electron tunnelling. The vertical manipulation scheme used here enables us to assemble nanostructures of diverse sizes and shapes with the In adatoms residing on vacancy sites of the (2?×?2)-reconstructed surface (nearest-neighbour vacancy spacing: 8.57??).     

Fabrication and modification of the supported Al nanoparticles on the Al(001) and (110) surfaces using the reversible vertical single-atom manipulation with the Cu and Pt trimer-apex tips: a first-principles study

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.     

Towards an understanding of surfactant action in the epitaxial growth of metals: The case of Sb on Ag (111)

We address the role of surfactant adsorbates in determining changes in the homoepitaxial growth mode of metals, discussing the case of Sb on Ag (111). From ab initio calculations, we extract evidence that the mechanism operative in this system is that Sb induces an irregular shape and an increase in density of the growing Ag islands, and an ensuing increase of the number of attempts for an adatom to descend to a lower terrace. This results from a combination of peculiar properties of this system: Sb is adsorbed insubstitutional surface sites, leading to the formation of a Sb–Ag surface alloy; deposited Ag has reduced mobility on Sb-covered Ag (111), from which follows a higher nucleation probability. The island shape is irregular since the surface alloy is disordered. Surface seggregation of Sb once the growing layer is completed furthers the phenomenon for many deposited Ag layers. Our explanation of the surfactant action of Sb on Ag (111) does not require a reduction of the downstep diffusion barrier, which may, however, be a concurrent factor helpful to interlayer mass transport and layerby-layer growth.     

Interfacial properties of Ce<Subscript>0.75</Subscript>Zr<Subscript>0.25</Subscript>O<Subscript>2</Subscript> supported noble metals (Pd,Pt) from first principles

First-principles electronic structure calculations of noble metals (NM=Pd, Pt)/Ce_0.75Zr_0.25O₂ systems are presented. It is found that: the NM adatoms do not prefer to stay at the atop or the bridge sites of the cations (Ce and Zr), but prefer to be adsorbed at or around the anion sites. The most preferable adsorption sites for both the Pd and Pt adatoms are the O-bridge sites neighboring the Zr dopant. The Pt adatom show much stronger interaction with the Ce_0.75Zr_0.25O₂(111) surface than does the Pd adatom. The interactions of the NM/Ce_0.75Zr_0.25O₂(111) interfaces are stronger than those of the corresponding NM/ceria(111) interfaces. There are some metal induced gap states (MIGS) appeared in the gaps of the NM/Ce_0.75Zr_0.25O₂(111) interfaces, which are important to catalytic properties of the NM/Ce_0.75Zr_0.25O₂(111) catalysts.     

替位杂质对低能Pt原子与Pt(111)表面相互作用影响的分子动力学模拟

采用嵌入原子方法的原子间相互作用势，通过分子动力学方法模拟了低能Pt原子与Cu，Ag，Au，Ni，Pd替位掺杂Pt(111)表面的相互作用过程，系统研究了替位原子对表面吸附原子产额、溅射产额和空位缺陷产额的影响规律，分析了低能沉积过程中沉积原子与基体表面的相互作用机理以及替位原子的作用及其影响规律.研究结果显示：替位原子的存在不仅影响着沉积能量较低时的表面吸附原子的产额与空间分布，而且对沉积能量较高时的低能表面溅射过程和基体表面空位的形成产生重要影响.替位原子导致的表面吸附原子产额、表面原子溅射以及空位形 关键词： 分子动力学 低能粒子 替位掺杂 表面原子产额 溅射 空位     

Mechanism of associative oxygen desorption from Pt(111) surface

Mechanism of the associative desorption of oxygen from the Pt(111) surface has been studied on atomic level by means of DFT/GGA calculations and kinetic Monte Carlo simulations. It has been found that two oxygen adatoms can occur, with sufficient probability, in neighboring on-top sites, which is essential for formation and subsequent evaporation of the oxygen molecule. Monte Carlo simulations have demonstrated effectiveness of this channel for O₂ formation on Pt(111) and strongly support the suggested model of associative desorption from transition metal surfaces.     

低能Pt原子与Pt(111)表面相互作用的分子动力学模拟

利用分子动力学模拟方法详细研究了低能Pt原子与Pt(111)表面的相互作用所导致的表面吸附原子、溅射原子、表面空位的产生及分布规律,给出了表面吸附原子产额、溅射原子产额和表面空位产额随入射Pt原子能量的变化关系.模拟结果显示:溅射产额、表面吸附原子产额和表面空位产额随入射原子的能量的增加而增加,溅射原子、表面吸附原子的分布花样呈3度旋转对称性质;当入射粒子能量高于溅射阈值时,表面吸附原子主要是基体最表面原子的贡献,入射粒子直接成为表面吸附原子的概率很小.其主要原因是:当入射粒子能量高于溅射能量阈值时,入射 关键词： 分子动力学 低能粒子 表面原子产额 空位缺陷 溅射     

Reliable lateral manipulation of a single Ag adatom on a Ag(1 1 1) surface with a trimer-apex tip

We study the reliability of the lateral manipulation of a single Ag adatom on a Ag(1 1 1) surface with the single-atom and trimer-apex tips based on molecular statics simulations using surface embedded-atom-method potential. The dependence of the manipulation reliability on tip height and orientation is investigated. For the single-atom tip the manipulation reliability increases monotonically with decreasing tip height, which is owing to the strengthened lateral tip-adatom interaction as the tip height lowers. For the trimer-apex tip, the manipulation reliability is sensitive to the tip orientation in the lower tip-height range, while in the higher tip-height range the manipulation reliability is independent of the tip orientation and moreover can be greatly improved due to the strong vertical attraction of the tip on the adatom as compared to the single-atom tip. We also compare these results to those for manipulating single Cu adatoms on the Cu(1 1 1) surface, reveal the underlying physics, and propose the method to improve the manipulation reliability for different systems.     

The adsorption behaviours of Pt adatom on pristine and defective bilayer graphene

The structural stability and electronic property of metal Pt atom anchors on two typical substrates (including the pristine and defective bilayer graphene, PBG and DBG) are studied using the first-principles calculations. For the PBG sheets, the Pt atom at the bridge site of bottom layer has only one stable adsorption, which is more stable than other sites of the top layer. For the DBG sheets, the doped Pt below defective site has the larger adsorption energy than that of the upper one. Compared to the isolated graphene films, the Pt(111) substrate-supported graphene systems have effect on the adsorption energies of Pt adatom to some extent, but it does not affect the most preferable configurations. Moreover, the diffusion pathways and energy barriers of Pt adatom on PBG and DBG substrates are comparatively investigated. For the DBG sheets, the Pt dopant has smaller diffusion barrier on upper layer than that of the intercalation process through the defective site. Therefore, the Pt dopant prefers to diffuse on the top layer and then forms the metal impurity. This work provides valuable information on understanding the formation process and intercalation mechanism of metal adatom on graphene sheets.