C60膜上金刚石的成核与生长形貌研究

本文研究了HFCVD系统中覆盖有C60膜的Si(100)衬底上金刚石的成核与形貌特征.结果表明,C60能大幅度提高金刚石成核密度;C60氢化预处理能大幅度促进金刚石成核,但要合理控制CH4的浓度和预处理时间;随衬底温度的升高,金刚石晶粒由球状变为菜花状聚晶.     

掺杂C60薄膜的制备及光电特性

在电弧法制备的过程中添加氮气或B2O3粉末,制备了氮、硼替位式掺杂C60.硼掺杂和氮掺杂C60均显示明显的半导体导电特性,且室温电导率比未掺杂C60薄膜提高1～2个量级.用共蒸发的方法制备出了硫掺杂C60薄膜,其电导率～温度曲线中存在一个过渡区,过渡区两侧表现出明显的半导体导电特性,这与掺入C60薄膜中的硫杂质的存在状态有关.其室温电导率比掺杂前提高4个量级,光致发光也明显增强.另外还报道了用离子注入和射频等离子体辅助真空沉积的方法制备掺杂C60薄膜的初步结果.     

Characteristic Interaction of Na-H-C60 and C60 with Hydrogen and Rare Gases

Abstract

Rare gases such as He, Ne and Ar are trapped in the lattice of solid C₆₀ and (NaH)₄C₆₀ under conditions of ambient temperature and pressure. The mass analyzed thermal desorption reveals that rare gases are desorbed above 400K and their desorption amounts are in nonstoichiometric level. Ar2p and Ar3s X-ray photoelectron spectra show large chemical shifts. These results suggest that He, Ne and Ar have charge and are in valence state.     

C60分子的电子传导和量子流分布研究

利用基于Green's function的tight-binding方法,对由两条原子线电极连接C60分子远端构成的电子传导系统进行了理论计算和数值模拟,得出了入射电子通过C60分子传输到远端点的电子传输谱.其结果揭示了电子传导过程中C60分子的开关特性,并且得出了电子传输能量与分子轨道共振时传输概率峰值的出现及振荡特征.利用Fisher-Lee关系式和量子流密度理论,在传输概率峰值的能量点E=-1.38eV处获得了C60分子内的量子流分布,给出了键量子流的最大值和最小值.对全部分子键上的量子流数值进行了图形模拟,其结果符合量子流动量守恒定律.     

In Situ FTIR,XPS, and STM Studies of the Nano-Structure of a Photopolymerized C60 Film

Abstract

The nano-structure of C₆₀ photopolymers has been investigated using in situ Fourier-Transform Infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning tunneling microscopy (STM). The FTTR and XPS studies revealed that the C₆₀ pholopolymer has a cross-linking via a [2+2] cycloaddition four-membered ring and formed a 2D rhombohedral structure when the polymerization was saturated. Using STM, we have successfully observed the direct real-space imaging of the C₆₀ dimers and trimers in a C₆₀ monolayer supported on a clean semiconductor surface.     

In Situ FT-IR Study of an Electron-Beam Induced Reaction of C60 Film

Abstract

The structural modification induced by electron-beam (EB) in a C₆₀ film and its kinetics have been studied using in situ high-resolution FT-IR spectroscopy. Similar to studies on photoirradiated K_xC₆₀ fim, was found that a coalescence reaction between adjacent C₆₀ molecules takes place. In order to investigate the interaction between an incident electron and Cgg molecules, the time-dependence of the amounts of C₆₀ on the EB irradiation was examined. It was found that the reaction rate exhibits a linear dependence on the reactant concentration and nonlinear dependence on the incident current.     

ZnO氧空位与掺杂原子相互作用第一性原理研究

利用第一性原理对Ag,N,K三种不同族元素掺杂氧化锌的电子结构进行了研究,计算了完整晶胞和存在氧空位缺陷时掺杂晶胞的品格结构、氧空位形成能、态密度及能带结构.氧空位会使受主掺杂的晶格常数及晶胞体积变大;在钾掺杂的晶胞中氧空位的形成能更低,更容易产生氧空位;三种不同的掺杂体系中,Ag掺杂的空穴电导率最高;最后分析了氧空位对三种掺杂体系导电性的影响.     

Crystal Structure of Europium C60 Compounds

Abstract

We have studied crystal structures of europium C₆₀ compounds by high resolution x-ray diffraction measurements. In the systematic synthesis of Eu _x C₆₀ for x (0 ≤ x ≤ 6), two stable phases appear at x = 3 and 6. Eu₆C₆₀ has a bcc structure, which is an isostructure to M ₆C₆₀ (M represents an alkali or alkaline earth metal). Eu₃C₆₀ has a superstructure derived by doubling the fcc pristine C₆₀ crystal along three principal axes. This superstructure comes from an ordering of cation vacancies, which is analogous to Yb_2.75C₆₀.     

The Electronic Structures of (PH4)3C60 and (ClO4)3C60

Abstract

We have studied theoretically the electronic structures of a hypothetical donor-type material, (PH₄)₃C₆₀, and a hypothetical acceptor-type material, (ClO₄)₃C₆₀ from first principles by using a full-potential linear-combination-of-atomic-orbitals method based on the density-functional theory within the local-density approximation. It is found that the charge transfer from the PH₄ molecules to the C₆₀ molecules is perfect while the charge transfer from the ClO₄ molecules to the C₆₀ molecules is not perfect. We compare the latter result with the electronic structures of two typical acceptor-type organic conductors, (TMTSF)₂ClO₄ and (TMTSF)₂PF₆, and discuss the differences.     

硅基片上C60薄膜的生长特性和结构特性研究

本文采用物理气相沉积(PVD)法在不同预处理的Si(100)衬底上沉积了C60膜,并利用AFM和XRD研究了其生长特征和结构特性.结果表明,C60膜的生长特性不仅与C60分子的移动性和衬底的表面性质等多种因素有关,而且还受衬底表面先前淀积的C60膜的有序性影响;H-Si(100)面上生长的C60膜与普通抛光Si(100)面上的相比更具有*2111*3取向.     

Investigation on sol–gel silica coatings for the protection of ancient glass: Interaction with glass surface and protection efficiency

To hinder the phenomenon of weathering of ancient stained glass, the present work proposes the application of sol–gel coatings to the glass surface. Previous investigations [1], [2], [3], [4], [5] and [6], in fact, show that sol–gel silica coatings do not change the appearance of artistic glasses when deposited on their surface. Moreover, the film thickness is so small (around 200 nm) and its composition and structure so compatible with that of the original glass, that the characteristics of the coating and original glass are not distinguishable. In this work, several recipes used to produce sol–gel coatings have been tested in order to understand their behavior when adopted for covering ancient weathered glass. The coatings are made of sol–gel silica prepared with two different catalysts: H⁺, Pb²⁺ and without catalyst. All the investigated samples show a good adhesion of the coating to the glasses used to simulate the behavior of ancient artefacts. The sol–gel silica coatings have been studied before and after accelerated ageing to test the resistance of the protective coatings to weathering. Another important index to test of the efficiency of the sol–gel coatings for the protection of an ancient glass is the lead ion mobility. In ancient stained glass, in fact, this element is present in the metallic lead network, in the grisaille paintings and constitutes a main component of many glass tesserae. The action of water on this highly mobile ion involves the degradation of the glass itself and the release of the ion in the rain solution. Ageing tests show the efficiency of H⁺ and Pb²⁺ catalyzed coatings and the inefficiency of the non-catalyzed sol–gel layers.     

Intercalation of O2 and its Effect on the Properties of C60 and C70 Solids

Abstract

The intercalation of O₂ in C₆₀ and C₇₀ solids have been studied. In both gas effusion spectra of C₆₀ and C₇₀ powder exposed to O₂ at room temperature, two evolution peaks of O₂ are found near 80 and 150°C. In both C₆₀ and C₇₀ powder, the peak near 80°C does not depend on a heating ratio and the peak near 150°C shifts to higher temperature with the heating ratio. The activation energy on diffusion of O₂ in C₆₀ and C₇₀ solids are ～0.27eV and ～0.46eV, respectively. The number of O₂ intercalated in C₇₀ powder is larger than that in C₆₀ powder. Electron spin density of 02-intercalated C₆₀ film is larger than that of C₇₀ film. The effect on the properties of C₆₀ and C₇₀ solids by the intercalation of O₂ are discussed.     

微机械构件表面激光诱导化学复合镀纳米C60晶体工艺及性能研究

采用化学镀的方法实现了纳米C60晶体的表面金属化,然后通过激光诱导的方法,在微细构件表面,化学复合镀覆了Ni-P/纳米C60的复合镀层.采用扫描电子显微镜和PLINT高温微动疲劳试验机对镀层的组织形貌和摩擦学性能进行了表征分析,并考察了工艺参数对其的影响,结果表明基于C60的特殊分子结构以及其在摩擦磨损过程中所起的作用,镀层的摩擦系数明显减小,耐磨性能显著提高.     

Investigation of the structure of C60 fullerene halides by the neutron and synchrotron diffraction methods

The crystal and molecular structures of bromofullerenes and chlorofullerenes, namely, C₆₀Br₆ · 0.5PhCl · 0.5Br₂, C₆₀Br₈ · TiBr₄ · Br₂, C₆₀Br₂₄ · Br₂, and C₆₀Cl₂₄ · TiCl₄, are determined and refined using neutron and synchrotron diffraction. The interatomic distances are determined with an accuracy higher than the accuracy in the determination of the corresponding parameters for the same molecular structures with the use of X-ray laboratory equipment.     

Preparation and Properties of One-Dimensional C60 Nano-Structure in a Zeolite FSM-16

Abstract

C₆₀ molecules were embedded in the pores of a zeolite FSM-16 by using a liquid phase method. The shift of photoluminescence spectra of C₆₀ solid embedded in FSM-16 was discussed using data of ESR, PDS and SAXS.     

金刚石单晶合成工艺与铁基触媒中初生Fe3C形貌的关系

利用光学显微镜和X射线衍射等手段,表征了高温高压下合成金刚石单晶时不同合成工艺的铁基触媒合金组织结构.结果发现:金刚石合成效果较好时的触媒组织中Fe3C呈规则的条状,而合成效果不好时的触媒组织中局部出现了不规则的团絮状Fe3C.分析认为,Fe3C在不同的结晶条件下表现出不同的生长行为,高温高压下金刚石单晶的生长与触媒中Fe3C的生长行为有密切关系.     

Occupied and Unoccupied Orbitals of C60 and C70

Abstract

The full spectrum of occupied and unoccupied σ and π orbitals is presented for solid C₆₀, C₇₀, and graphite, using Cls emission and absorption spectroscopy. There are significant diffcrences between C₆₀ and C₇₀, and even larger changes relative to their infinite analog graphite (C∝). A comparison is made with photocmission and inverse photoemission results, along with first principles quasiparticle calculations.     

On the Binding Energy of Clusters with a Small Number of Lithium Atoms and Varying Scope of Interaction Between the Atoms. Hückel Molecular Orbital Approximation

The effect of the scope of interaction between the atoms in two-dimensional and threedimensional clusters containing 6, 7, 9, 10, 15 and 16 lithium atoms, upon the binding energy (BE) of the clusters has been investigated. BE of the clusters was calcuated by the HÜCKEL Molecular Orbital (HMO) method. It has been established that for clusters with the same number of atoms BE has its maximum value when the interaction of each atom of the cluster with the atoms of its first and second coordination spheres in the lithium lattice are taken into account. After the maximum BE decreases and tends to a constant value which is attained when the interaction of each atom of the cluster with the atoms of its six coordination spheres is taken into account. The reasons for the above result should be looked for in the limits of applicability of the calculation procedure based on the HMO method to the study of properties of various models of clusters containing a small number of metal (e.g. lithium) atoms.     

锑烯表面碱金属原子吸附和扩散行为研究

锑烯是一种新兴的具有多种新奇特性的二维材料.本文基于密度泛函理论的第一性原理方法,主要研究了Li、Na、K原子在锑烯表面的吸附和扩散行为.结果显示,Li、Na、K原子在锑烯表面吸附时,具有较大的吸附能,分别为-2.36 eV,-1.84 eV和-1.60 eV.通过引入垂直于衬底指向吸附原子的外电场,发现它们的吸附能和转移电荷都随着外加电场的增加而增加,其中对K原子的吸附能和转移电荷影响最显著.采用Climbing Image-NudgedElastic Band (CI-NEB)的方法研究得出Li、Na和K在锑烯表面的扩散行为都具有较小的扩散势垒,其中Li为0.09eV,Na为0.08 eV,而K仅有0.04 eV,这有利于碱金属原子在锑烯表面的扩散.研究结果为进一步了解锑烯的性质和应用推广提供了基础理论支持.     

TEM Investigation of Stacking Faults in the Superconducting Compound YNi2B2C

To evaluate the influence of composition and high-temperature heat treatment on the occurrence of stacking faults and intergrowths in the layered superconducting compound YNi₂B₂C a series of polycrystalline samples and a single crystal were investigated by TEM. Stacking faults were found in the most inhomogeneous sample only, which was annealed at 1100°C. Homogenisation at temperatures of 1450°C and higher results in a recovery of stacking faults. The observed faults should develop during crystallisation by formation of extra planes of YC or Ni₂B, resulting in a local deviation from the stoichiometric composition. In highly faulted areas the distance of stacking faults was about 50nm. These faults have apparently no influence on the superconduction transition temperature T_c.