Growth kinetics of graphene and graphite films on the \operatorname{Re} (10\bar 10) surface

Growth kinetics of graphene and graphite layers on the surface of carbon-saturated rhenium has been investigated. The experimental data agree well with the results of the mathematical analysis of diffusion processes in the metal bulk with the participation of carbon atoms and the subsequent precipitation of carbon on the surface. It has been established that graphene layers of rigorously specified thickness in the range of 1–50 layers can be grown on metal in the temperature range of 1300–1500 K.     

Graphene traps for cesium atoms

A significant increase in the surface concentration of cesium atoms intercalated under graphene islands on rhodium has been revealed when annealing the adsorbed layer in a ultrahigh vacuum. Heating leads to a decrease in the area of graphene islands due to the solution of carbon atoms in the metal bulk. At the same time, the edge carbon atoms in the islands, which are coupled with the surface by chemisorptive forces, prevent the leakage of the alkali metal from under the islands. This leads to the significant compression of cesium and to an increase in its surface concentration under the islands by a factor of almost 10. The desorption of cesium is observed only after the complete thermal destruction of graphene islands.     

Calculation of the energy of binding of titanium and scandium complexes to the surface of carbon nanotubes

Complexes of zigzag-type carbon nanotubes (CNTs) with transition metal atoms, scandium and titanium, were studied. It was demonstrated that the energy of binding of both atoms with a carbon surface decreases whereas the rate of diffusion along the surface increases with increasing nanotube diameter. The rate constant of migration of scandium atoms over a CNT surface are several orders of magnitude higher than that for titanium atoms, because the CNT surface—Sc atom binding energy is substantially lower.     

Graphene growth during benzene pyrolysis on an iridium crystal

The dependence of graphene formation mechanisms during pyrolysis of carbon-containing molecules on iridium on the crystal structure and surface curvature has been studied using field desorption and field electron microscopy. The structure and shape of grown carbon formations, diffusion, desorption, and intercalation of alkali metal atoms have been investigated.     

Comparison of metallic silver and copper doping effects on single-walled carbon nanotubes

In this work we performed the filling of single-walled carbon nanotube channels with metallic silver and copper by means of two-step synthesis including imbuing with metal nitrate aqueous solution and further annealing. It has been shown that metal insertion into the nanotube cavities results in the Fermi level upshift and the charge transfer from metal to carbon atoms, thus donor doping of single-walled carbon nanotubes takes place. At the same time, encapsulated silver has a larger donor effect on the carbon nanotubes that has been proved by Raman spectroscopy and X-ray photoelectron spectroscopy.     

Anti-prismatic modifications of single-walled carbon nanotubes and their electronic properties: Regular adsorption of fluorine atoms on graphene surfaces of nanotubes

The regular adsorption of fluorine atoms on the surfaces of single-walled carbon nanotubes along their cylindrical axes leads to a modification of cylindrical carbon skeletons of these single-walled carbon nanotubes into carbon skeletons that have a nearly “anti-prismatic” shape (anti-prismatic modifications). In the faces of these modified single-walled carbon nanotubes, there can arise quasi-one-dimensional isolated carbon conjugated subsystems (tracks) with different structures. Model fragments of nanotubes of the (n, 0) type that contain up to 360 carbon atoms and their derivatives with regularly adsorbed fluorine atoms on the graphene surface have been calculated using the semiempirical PM3 method. It has been found that the main properties of the single-walled carbon nanotubes modified by the above method are determined by the character of the conjugation of the electrons in isolated carbon tracks, which is close to the character of the conjugation of the electrons in the initial single-walled carbon nanotubes.     

Evidence for shakeup satellites due to surface contamination in arsenic metal and its compounds

Satellites accompanying the main peaks have been observed in the X-ray photo-electron spectra of arsenic metal and its compounds. These satellites are examined in terms of various mechanisms such as multi-electron excitation energy losses. In addition to plasm on satellites, a satellite doublet associated with the 3d peak is attributed to charge-transfer shakeup from the 2pσ level of carbon (present as a surface contamination) to the Fermi level of arsenic. Such charge-transfer shake-up satellites may be caused by a difference in the relaxation energy of surface arsenic atoms as compared to bulk arsenic atoms resulting from the presence of weakly bonded carbon.     

Effect of coverage by carbon on the possibility of forming an interstitial solid solution in Fe(001) and Fe(111) subsurface layers

The interaction between carbon adatoms as a function of the coverage of the Fe(001) and Fe(111) surfaces by carbon has been theoretically investigated using first-principles calculations in terms of the density functional theory. It has been established for the first time that the sequential filling of the upper surface layer by carbon atoms leads to the embedding of a part of atoms in the subsurface iron layer due to the their collective interaction, which provides the possibility of forming the interstitial solid solution. It has been demonstrated that the high coverage of the (001) surface by carbon leads to a considerable decrease in the energy barrier to the diffusion of carbon atoms into the subsurface layer as compared to the diffusion barrier for single atoms.     

T型石墨烯及其衍生物的结构与电子特性

采用基于密度泛函理论的第一原理方法研究了T型石墨烯及其衍生物-n(n=1—5)的结构稳定性和电子结构性质.T型石墨烯是一种拥有四角形环的二维碳材料同素异构体,通过改变连接四角形环的碳链上的碳原子个数n,可以得到一系列的sp-sp~2杂化结构,称其为T型石墨烯衍生物-n.计算结果表明:这些材料的结构稳定性、化学键类型和电子结构性质都依存于n的奇偶性.其中T型石墨烯(n=0)的结构最稳定,并形成一个由8个碳原子构成的大环.声子谱计算的结果表明,n为偶数时的体系具有动力学稳定性,而n为奇数时的体系则是不稳定的.n为偶数时体系四角形环之间的碳链上的化学键呈单、三键交叉排列,体系显示为金属性特征,且随着n的增大,体系的金属性加强.n为奇数时体系四角形环之间的碳链上的化学键则为双键连续排列,体系呈金属性且具有磁性(n=1除外).研究表明该系列材料作为一种新的二维碳材料同素异构体,具有独特的结构和丰富的电子结构特性,很可能在纳米器件中得到广泛应用.     

The interaction of Cr(CO)3 on the (n, 0) nanotube side-walls: a density functional study through a cluster model approach

Density functional calculations have been performed to investigate the functionalization of single-wall carbon nanotubes (SWNTs) with the Cr(CO)₃ metal fragment, employing extended molecular models. A circumcoronene molecule (C₅₄H₁₈), made by the fusion of 19 hexagonal carbon rings, can be regarded as a fragment of a graphene sheet. To reproduce the curvature of the SWNT surface, suitable geometric constraints have been imposed on the C₅₄H₁₈ model, freezing the positions of the outer hydrogens along the directions of the nanotube C-C bonds. Geometry optimizations have then been performed under this constraint on the Cr(CO)₃-C₅₄H₁₈ complexes, pointing out the most favourable coordination sites on the hexagonal rings of the carbon atom surface and the electronic properties of the resulting system. The effect of the curvature on the metal coordination to nanotubes has been analysed by investigating the interaction of the Cr(CO)₃ metal complex with the C₅₄H₁₈ molecules, modelling (n, 0) nanotubes with different degrees of curvature, i.e. with various values of the chiral vector (n, 0).     

Metal atom catalyzed enlargement of fullerenes

A metal catalyzed enlargement of fullerenes has been demonstrated by in situ high-resolution transmission electron microscopy. It was found that carbon atoms and clusters can be continuously incorporated into a closed fullerene cage at a high temperature, leading to an increase in the diameter and consequently the formation of giant fullerene with the assist of adsorbed metal atoms. Density functional theoretical simulations indeed suggest that the activation energy for the carbon incorporation and the associated Stone-Wales transformation can be substantially reduced due to the presence of metal atoms, which should be of key importance for the fullerene growth.     

Proton and Carbon - 13 NMR Assignments for Fluorinated and Nonfluorinated Aromatic Ketimines

The ¹H and ¹³C NMR spectra of three aromatic ketimines with varying degrees of fluoro substitution have been extensively studied using one and two dimensional techniques. COSY experiments were conducted to identify the protons on each of the aromatic groups, HETCORR experiments were then utilized to identify the corresponding carbon atoms, and then the order of the carbon atoms was established by long-range HETCORR (HRTCORRLR) results. These studies have allowed rigorous assignments to be made for most of the carbon and hydrogen atoms present in these compounds. Fluorine splittings were very helpful in the analyses. In the course of this study, the NMR absorbances (¹H and ¹³C) of related aldimines have also been assigned. This constitutes the first report on the assignments of ¹H and ¹³C absorbances for ketimines. The observed spectral properties suggest that the structure of aromatic ketimines is one in which the aromatic rings are in three different planes. Two of the aromatic rings, the N-substituted ring and the C-substituted ring in the cis configuration, are twisted substantially out of the plane with respect to the -C=N- bond. The remaining C-substituted aromatic ring, trans to the N-substituted ring, lies in the deshielding zone of the imine bond.     

Physicochemical processes in multiphase systems on metal surfaces containing nano-carbon: Segregation,dissolution, graphene nucleation,and growth

A carbon phase equilibria on the surface of metals during graphene nucleation and initial graphite growth is considered thermodynamically. Three phases are shown to be necessarily taken into account: C atoms dissolved in a metal substrate bulk, C atoms chemisorbed on the surface, and graphene (polycondensed carbon phase). Applicability of the Gibbs phase rule to this particular case is analyzed, with surface tension taken into account as an independent thermodynamic degree of freedom. A specific role of boundary atoms of graphene islands, which can be considered (with some limitations) as an independent quasi-1D phase is revealed.     

RHEED study of the (1 1 0) cleavage surface of CdTe:Cr single crystals

The structure of (1 1 0) plane of Cr-doped CdTe single crystals has been studied by reflection high energy electron diffraction and scanning electron microscopy. Diffraction patterns consist of diffraction spots and Kikuchi lines. However, for very small incident angle, the Debye rings are observed. The constant lattice attributed to these rings is 0.8% less then for pure CdTe. These anomalous properties of the near surface layer are likely to occur due to the concentration of Cr atoms creating compressive surface strains or the effect of crystal cleavage.     

Role of edge atoms of graphene islands on metals in nucleation,growth, alkali metal intercalation

Physics of the Solid State - The effect of edge carbon atoms in graphene islands grown on a metal surface on the kinetics of nucleation, growth and dissolution of these islands, as well as of a...     

ZA27/CNT界面特性电子理论研究

依据原子结合能定义了界面结合能. 采用递归法计算了纳米管增强锌铝基复合材料中ZA27/CNT界面电子结构，揭示了纳米管在ZA27合金晶界分布的微观物理本质，及其ZA27/CNT弱界面结合的电子层面的原因. 研究发现：金属基体对纳米管增强相上的碳原子态密度影响很大，而纳米管对基体金属中的铝、锌原子影响很小. 碳原子态密度与基体金属原子趋于同化，使纳米管与基体金属结合，但因同化程度不高导致界面结合较弱，影响强化效果. 如果在纳米管装饰或镀上与基体金属性质相近的原子层，会极大改善复合材料的界面结合强度，提高复合材料性能. 关键词： 复合材料 纳米管 电子结构 界面     

碳纳米管负载矾的第一性原理研究

本文基于密度泛函第一性原理研究了原始和带有缺陷的(Stone-Wales缺陷和单空位缺陷)碳纳米管负载金属V的稳定构型.对于V吸附在原始碳纳米管(CNT)上时,V在内表面的吸附比外表面的吸附有更强的相互作用力,且六元环内表面结构最稳定.当V与Stone-Wales缺陷碳纳米管相互作用时,V原子易吸附在管外七元环C-C键的外表面和内表面处,这说明缺陷位置的有效结合使之局域化加强.而以单空位缺陷碳纳米管为载体时V最易吸附在外缺陷处,相当于碳纳米管的一个C被金属V原子取代,形成了3个V-C_(sur)键,这进一步表明SV管外吸附比管内吸附更容易.我们从上述三种构型载体中发现,金属V吸附在缺陷碳纳米管时的稳定性要优于原始碳纳米管,且SV缺陷对金属V的固定效果最好.     

Scattering of O? from a graphite surface

Recently an extensive series of measurements has been presented for the angular distributions of oxygen molecules scattered from a graphite surface. Incident translational energies ranged from 291 to 614 meV with surface temperatures from 150 to 500 K. The measurements were taken with a fixed angle of 90° between the source beam and the detector and the angular distributions consisted of a single broad peak with the most probable intensity located at an angle slightly larger than the 45° specular position. Analysis with the hard cubes model for atom-surface scattering indicated that the scattering is primarily a single collision event with a surface having a collective effective mass much larger than a single carbon atom. Limited analysis with a classical diatomic molecular scattering theory was also presented. In this paper a more complete analysis using the classical diatomic molecular scattering theory is presented. The energy and temperature dependence of the observed angular distributions are well described as single collision events with a surface having an effective mass of 1.8 carbon graphite rings. In agreement with the earlier analysis and with other experiments, this suggests a large cooperative response of the carbon atoms in the outermost graphene layer.     

Carbon clusters near the step of Rh surface: implication for the initial stage of graphene nucleation

To understand the initial nucleation of graphene by chemical vapor deposition along metal step, carbon clusters (N = 1 ～ 24) near Rh (4 3 3) stepwise surface were systemically explored by first-principles calculations. Carbon chains are always more stable than carbon rings on stepped metal surface. Starting from C₆, carbon chains prefer two-end passivation on the metal step. A structural transition of carbon clusters from one-dimensional sp chains to two-dimensional s p ² networks are found at C₁₀, which corresponds to the nucleation size at a wide range of chemical potentials. According to these theoretical results, we proposed that appropriately controlling the chemical potential may be helpful for observing the four stable carbon clusters along metal step and improving the quality of graphene.     

Effect of the gaseous medium in the process of rolling on the microhardness of aluminum and iron

The load dependence of the microhardness of polycrystalline aluminum and iron specimens produced by rolling in a nitrogen, helium, or air medium has been investigated. It has been found that nitrogen and helium have different effects on the microhardness of these metals in the low-load range. This difference is associated with the specific features in the intensity of dynamic penetration of nitrogen and helium into the surface layer of aluminum and iron, which depends on the initial defect crystal structure of the metals, as well as on the type of bonding of helium atoms and nitrogen molecules with metal atoms. It has been shown that the effect of the gaseous medium of the rolling on the microhardness manifests itself only in a very thin surface layer of metal specimens, where the microhardness exhibits a size effect, and an increase in the microhardness indentation depth remains unchanged with an increase in the load and does not depend on the gaseous medium of the prerolling of the specimens.