Chemical and physical interactions at metal/self-assembled organic monolayer interfaces

The purpose of research on metals (M) deposited onto self-assembled monolayers (SAMs) is to understand the interactions between metal (M) and eventually metal oxide overlayers on well-ordered organic substrates. Application of M/SAM and inorganic/SAM research results to the understanding of real inorganic/ organic interfaces in vacuum and under environmental conditions can potentially play a key role in the development of advanced devices with stable interfacial properties. The M/SAM approach to interface research is delineated as a new subfield in surface science in the context of other approaches to inorganic/organic interface research. Current issues in M/SAM research are outlined, including chemical compound formation, the morphology (spreading, clustering, or penetration) of the metal species, the kinetics of the metal morphology, the effect of the metal on the degree of order in the SAM, and the rate of metal penetration into the SAM. Probes are recommended that are suitable for M/SAM research. The results of M/SAM studies to date are reviewed, and M/SAM combinations are ranked according to reactivity and penetration. Key probes for addressing gaps in the research results are identified. The effects of defects, disordering, air exposure, and X-ray and electron beam exposure on the experimental results to date are evaluated. Thus far, the results have successfully revealed qualitative relationships of M/SAM chemistry, temperature, and penetration. The chemical interactions that have been found are applicable to real M/polymer interfaces as formed in vacuum. It has yet to be shown that M/SAM research will yield quantitative understanding of interface formation or that M/SAM interfaces are entirely analogous to M/polymer interfaces in the details of interface formation. The future of this subfield of surface science lies in its expansion from M/SAM interfaces in vacuum to other inorganic/SAM interfaces in vacuum and, eventually, under environmental conditions.     

Internal mechanical stresses and the thermodynamic and adhesion parameters of the metal condensate-single-crystal silicon system

The kinetics of generation of internal mechanical stresses ??(d) in chromium, copper, gold, and aluminum thin films on single-crystal silicon substrates at different deposition rates has been experimentally investigated using the cantilever method. A two-step character of the variations in internal tensile stresses has been revealed. The regularities of the formation of the maximum level of mechanical stresses in the condensates under investigation have been established. The energy and adhesion parameters of chromium, copper, gold, and aluminum nanolayers on silicon, germanium, and nickel substrates have been studied using the macroscopic methods of surface physics. The interfacial energy, interfacial tension, work of adhesion, interfacial charge, and a new energy characteristic of the interfacial layer, namely, the energy of adhesive bonds, which exceeds the interfacial energy, have been determined.     

聚合物分子与官能化纳米管相互作用及扩散特性的分子动力学模拟

用全原子分子动力学方法研究典型聚合物分子（PE,PEO和PP）与碳纳米管（CNT）及官能化碳纳米管（FCNT）界面的相互作用及扩散特性.动力学模拟显示：—CH₃官能团具有减弱CNT与PE和PP的相互作用,但是,—CH₃官能化后的CNT与PEO之间确有增强作用.分析含氧官能团（—OH和—COOH）官能化的CNT与PE,PEO和PP的相互作用,可知含氧官能团的确具有增强表面相互作用的功能,而且含氧原子越多,相互作用就越强.此外,—CH₃,—OH,—COOH官能化后的CNT与PE,PP和PEO体系的总能量均减少,而且能量满足—COOH < —OH < —CH₃.分析非键相互作用势（库仑能和范德瓦尔斯能）,可知库伦相互作用是增强界面相互作用的主要作用能.官能化后的CNT/PE,CNT/PEO,CNT/PP体系的扩散系数都明显减小,且扩散系数大小满足—COOH < —OH < —CH₃.     

Enhanced material classification using turbulence-degraded polarimetric imagery

An enhanced material-classification algorithm using turbulence-degraded polarimetric imagery is presented. The proposed technique improves upon an existing dielectric/metal material-classification algorithm by providing a more detailed object classification. This is accomplished by redesigning the degree-of-linear-polarization priors in the blind-deconvolution algorithm to include two subclasses of metals--an aluminum group classification (includes aluminum, copper, gold, and silver) and an iron group classification (includes iron, titanium, nickel, and chromium). This new classification provides functional information about the object that is not provided by existing dielectric/metal material classifiers. A discussion of the design of these new degree-of-linear-polarization priors is provided. Experimental results of two painted metal samples are also provided to verify the algorithm's accuracy.     

Phase transition of nano-sized amorphous tungsten to a crystalline state

We study thermal-physical characteristics of nano-sized amorphous tungsten and of its oxide. It is shown that a nano-size amorphous metal gets into a nano-size crystalline state after heating up to temperatures much lower than the half-temperature of melting, which is typical for all nano-size amorphous materials. Phase transition of amorphous nano-size WO₂ into crystalline state occurs in the temperature range 350–520°C, while the same transition in case of W takes place in the range 1000–1370°C. The energy released at crystallization of nano-size amorphous metal amounts to 170±25 J/g coinciding practically with the value of specific melting heat of usual tungsten. Such a high additional energy of nano-size amorphous metals above the energy of nano-size crystalline metals is their main peculiarity which widens essentially the range of their practical applications.     

用离子辐照模拟研究反应堆结构材料中金属/金属界面原子扩散行为

介绍了利用载能离子辐照模拟研究反应堆结构材料中金属／金属界面原子扩散行为的实验进展,特别是辐照参数（如辐照剂量、辐照温度、核能损、电子能损以及膜结构等）对界面原子扩散行为的影响,并对可能的机理进行了简要的评述。 Atom diffusion at metal/metal interfaces is very important for property of reactor structural materials, which can be simulated by using energetic ion irradiations. The present situation of experimental studies on atom diffusion at metal/metal interfaces induced by energetic ion irradiations is reviewed. The influence of experimental parameters such as the irradiation dose, irradiation temperature, electronic energy loss, nuclear energy loss and the interface structure on the intermixing is emphatically introduced. In addition, the possible mechanisms of metal/ metal intermixing are also briefly described.     

非水体系的表面增强拉曼光谱研究

本文主要报告了本研究小组自八十年代末至今应用SERS效应对电极/非水溶液界面现象进行研究的一些结果。研究电极从具有强SERS效应的金、银、铜等贵金属,拓宽至铁、镍、铂等过渡金属。借助非水体系SERS的特殊性,我们主要开展了非水体系中溶剂的界面特性、溶质的表面吸附及表面化学反应如C1分子在铂族金属表面的解离反应等研究。此外,对作为非水体系中无法彻底去除的水分子的表面吸附模型也进行了较详细的研究。     

Crystallization behavior and origin of c-axis orientation in sol–gel-derived ZnO:Li thin films on glass substrates

Preferentially, c-axis-oriented lithium-doped zinc oxide (ZnO:Li) thin films were prepared on Pyrex borosilicate glass substrates by a sol–gel method starting from zinc acetate dihydrate, lithium chloride, 2-methoxyethanol and monoethanolamine. Decomposition and crystallization behavior of dip-coated amorphous precursor films during post-annealing treatments were investigated by thermogravimetry–differential thermal analysis (TG–DTA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), optical transmittance measurements, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). It was revealed that the films contained the organic compounds at temperatures up to 300°C, which was the key to the transformation from the amorphous to the crystalline state. Thermodynamical consideration of nucleation and crystal growth was made taking account of surface energies of the film and the glass substrate and an interfacial energy between them. Mechanisms underlying the c-axis orientation were proposed based upon the initial orientation due to nucleation and final growth orientation.     

一种计算固体冷能、冷压和结合能的新方法

 给出了利用Hugoniot参数计算材料冷能、冷压和结合能的一种新方法，对52种纯元素单质固体材料的计算表明，该方法的计算误差较小，对计算碱金属等外层电子数较少的材料效果尤佳。利用文中给出的冷能、冷压公式，计算出的铝、铜、银和锌等材料的冲击绝热线与实验数据符合得非常好。     

Modelling temperature and concentration dependent solid/liquid interfacial energies

Models for the prediction of the solid/liquid interfacial energy in pure substances and binary alloys, respectively, are reviewed and extended regarding the temperature and concentration dependence of the required thermodynamic entities. A CALPHAD-type thermodynamic database is used to introduce temperature and concentration dependent melting enthalpies and entropies for multicomponent alloys in the temperature range between liquidus and solidus. Several suitable models are extended and employed to calculate the temperature and concentration dependent interfacial energy for Al–FCC with their respective liquids and compared with experimental data.     

Mode I and Mode II interlaminar fracture toughness of CFRP/magnesium alloys hybrid laminates

The fiber metal laminates (FML), consisting of carbon fiber reinforced polymer prepregs and magnesium alloys sheets, were introduced, and the Mode I (peel) and Mode II (shear) interlaminar fracture toughness of the FMLs were investigated. The results show that the Mode I interlaminar toughness (0.23 kJ/m²) of the FMLs is much lower than the Mode II interlaminar toughness (5.81 kJ/m²), due to the fact that the effects of mechanical interlock to hinder crack propagates is smaller under Mode I loading conditions than under Mode II. The FMLs mainly show adhesive failure and interfacial failure under Mode I loading conditions, while for Mode II loading, it exhibits a degree of epoxy cohesive failure except the adhesive failure and interfacial failure.     

Measurement of the interfacial energy between amorphous Si and crystalline Si

The experimental data of crystallization of amorphous Si thin films on single crystal Si substrates and on inert substrates have been analysed by a kinetic model of phase transformation. On the basis of the analysis, the interfacial energy between amorphous Si and crystalline Si has been calculated to be about 0.30 eV/atom and the number of Si atoms in the critical nucleus to be about 110.Dedicated to H.-J. Queisser on the occasion of his 60th birthday     

Contact improvement of carbon nanotubes via electroless nickel deposition

Individual multi-walled carbon nanotubes (CNTs) were deposited onto microelectrodes and embedded in nickel to achieve low-ohmic contact resistances. Electroless deposition of nickel onto gold/iron, palladium, and cobalt microelectrodes was used to form electrically stable bonds at the interfaces between the electrodes and CNTs. Resistance measurements showed that the contact resistances of the CNTs on gold/iron and palladium were significantly improved by nickel embedding, whereas no further improvement was found for the CNTs on cobalt. Electroless metal deposition is a parallel process providing stable electrical and mechanical contacts between CNTs and metallic microelectrodes. PACS 81.07.De     

Modeling of silicon-nanocrystal formation in amorphous silicon/silicon dioxide multilayer structure

The formation process of silicon-nanocrystals （Si-NCs） in the amorphous silicon/silicon dioxide （a-Si/SiO2） multilayer structure during thermal annealing is theoretically studied with a modified model based on the Gibbs free energy variation. In this model, the concept of average effective interfacial free energy variation is introduced and the whole formation process consisting of nucleation and subsequent growth is considered. The calculating results indicate that there is a lower limit of the silicon layer thickness for forming Si-NCs in a-Si/SiO2 multilayer, and the oxide interfaces cannot constrain their lateral growth. Furthermore, by comparing the results for a-Si/SiO2 and a-Si/SiNx multilayers, it is found that the constraint on the crystal growth from the dielectric interfaces depends on the difference between interfacial free energies.     

Electronic States and Schottky Barrier Height at Metal/MgO(100) Interfaces

Using an ab initio total energy approach, we study the electronic structure of metal/MgO(100) interfaces. By considering simple and transition metals, different adsorption sites and different interface separations, we analyze the influence of the character of metal and of the detailed interfacial atomic structure. We calculate the interface density of states, electron transfer, electric dipole, and the Schottky barrier height. We characterize three types of electronic states: states due to chemical bonding which appear at well defined energies, conventional metal-induced gap states associated to a smooth density of states in the MgO gap region, and metal band distortions due to polarization by the electrostatic field of the ionic substrate. We point out that, with respect to the extended Schottky limit, the interface formation yields an electric dipole mainly determined by the substrate characteristics. Indeed, the metal-dependent contributions (interfacial states and electron transfer) remain small with respect to the metal polarization induced by the substrate electrostatic field.     

Amorphous hydrogenated carbon films on semiconductors

The adhesion quality of amorphous hydrogenated carbon films (a-C:H) on semiconductor substrates depends to a large degree on the properties of the interface. The present work complements the photoemission results of the preceding paper with a detailed investigation of the atomic structure of the a-C:H/Si and a-C:H/GaAs interfaces. We show that the method of substrate cleaning and the deposition parameters affect the thickness of the interfacial layer and the interface roughness. The carbide compounds that form in the interfacial layer are found to be amorphous and we present evidence for the precipitation of metallic Ga at the a-C:H/GaAs interface. Finally, we have determined the extent of atomic intermixing in the interfacial region and compare our results with different mechanisms of adhesion.     

Structure of metal nanowires in nanoporous alumina membranes studied by EXAFS and X-ray diffraction

The structure of nanowires of different metals grown within nanoporous alumina membranes has been studied by EXAFS, WAXS and high energy X-ray diffraction. Nanowires of gold, silver, copper and iron adopt the lattice structure and bond distances of the bulk metals. Cobalt nanowires on the other hand were composed of a mixture of hcp phase, stable at room temperature, and fcc phase, which in bulk cobalt is normally stable only at high temperatures, in a ratio depending on the pore size. The nanowires are non-continuous but are made of nanocrystallites whose shape and size was found to depend strongly on the metal. All the metals except gold showed the presence of a preferred orientation which was slight in the case of Ag and Cu but much stronger in the case of iron and cobalt nanowires. Received 30 November 2000     

Anisotropy of the interface energy of IA and IB metals at a boundary with organic liquids

A statistical electron technique for calculating the interface energy at a boundary with nonpolar organic liquids is proposed in the context of the Frenkel–Gambosh–Zadumkin theory. The anisotropy of the interface energy is determined. The general dependences of the interface energies of alkali metals, copper, silver, and gold on temperature, the atomic numbers of metals, and the dielectric permeability of the organic liquid are found.     

Crystalline and relaxation properties of ethylene copolymer films inserted between two steel sheets

The relaxation and crystalline properties of ethylene vinyl acetate (EVA) co-polymers inserted in steel/polymer/steel assemblies were studied. To investigate the properties of the interfacial region, polymers of different thickness inserted in the assemblies were analyzed. The studied EVA copolymers are semicrystalline polymers. The relaxation properties of the amorphous phase were investigated by dynamic mechanical measurements performed on the steel/polymer/steel assemblies, and the crystalline properties were studied by differential scanning calorimetry (DSC). The results indicate that, for low polymer thicknesses, the mobility of the amorphous phase is significantly reduced. Significant changes in the crystalline organization also were observed when the polymer thickness decreased, with the presence of more numerous disorganized crystals for thin EVA layers. These crystals can act as physical ties that reduce the mobility of the neighboring amorphous chains. These results indicate the formation of an interphase layer of reduced mobility.     

复合空心立方银/金属纳米材料的制备及其SERS表征

本文用一锅法, 以立方银纳米材料为模板, 通过置换反应成功制备了空心的立方银/钯(Ag/Pd)、银/铂(Ag/Pt)和银/金(Ag/Au)纳米材料, 并将它们作为基底(以KSCN作为探针), 检测其SERS信号。