低能CU6团簇在CU(001)表面和AU(001)表面沉积的分子动力学模拟研究

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扫描隧道显微镜和原子力显微镜

 在微观领域对物质进行观察和研究中,人们发明了各种显微镜。但是光学显微镜由于受到光的波长的限制而无法达到很高的分辨率,Ｘ射线衍射技术则要求观察样品必须是晶体,透射电镜则需要对观察样品进行超薄切片。所有这些要求使人们的观察受到了限制,因此人们开始研制更加先进的显微镜。１９８２年宾尼格、罗雷尔及其同事们成功地研制出世界上第一台扫描隧道显微镜（ＳＴＭ）,导致了显微领域中的一场革命,并在它的基础上研制出一系列的扫描探针显微镜,如原子力显微镜、磁力显微镜和激光力显微镜等。ＳＴＭ的出现使人类第一次可以实时地观测单个原子在物质表面的排列状态和与表面电子行为有关的物理性质和化学性质。     

Study on the Reaction Mechanism for Carbon Dioxide Reforming of Methane over supported Nickel Catalyst

The adsorption and dissociation of methane and carbon dioxide for reforming on nickel catalyst were extensively investigated by TPSR and TPD experiments. It showed that the decomposition of methane results in the formation of at least three kinds of surface carbon species on supported nickel catalyst, while CO2 adsorbed on the catalyst weakly and only existed in one kind of adsorption state. Then the mechanism of interaction between the species dissociated from CH4 and CO2 during reforming was proposed.     

金属表面在反射方向产生光学二次谐波的研究(Ⅱ)

利用不同偏振态入射光在银和铝表面上产生的光学二次谐波.本实验对这些金属的表面非线性极化源进行了研究.实验结果表明,Rudnick和Stern引入的、描述垂直于金属表面的面谐波电流的唯象参数“α”,应在-2和-7之间(倍频光波长为0.532μm).这与过去理论计算及实验测量值都有较大的不同;实验结果还表明,参数α值随入射角略有变化.本实验还首次验证了,衡量平行于金属表面的面谐波电流的唯象参数b≈-1的理论计算值.     

Adsorption geometry of glycine on Cu（001） determined with low—energy electron diffraction and scanning tunnelling microscopy

Using low-energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) it has been found that glycine molecules adsorbed on Cu(001) can form but only the (2×4) and c(2×4) superstructures. On the basis of the missing LEED spots of the surface, it has been concluded that: each (2×4) unit cell consists of two molecules, one being the mirror image of the other; the C－C axis of both molecules lies in the mirror plane of the Cu substrate without a significant shift and twist from the plane; and the two O atoms of the carboxylate group of both molecules locate at the same height level without significant buckling. According to these conclusions, a structural model has been proposed for the (2×4) superstructure (a model for the c(2×4) superstructure already exists). We argue that the (2×4) and c(2×4) superstructures must have similar specific surface free energy, that their hydrogen bonds must be of N-H-O_II type, and that their local adsorption geometry must be similar or even the same. The advantage of combining STM with LEED to determine surface structures is clearly demonstrated.     

等离子体金属表面氮化中放电温度对氮原子态粒子的影响

采用快电子和重粒子(N₂⁺,N⁺,N_f)混合的Monte Carlo模型,研究了氮直流辉光放电等离子体金属表面氮化过程中.e-N_2s及N₂⁺-N_2s两种碰撞离解过程产生的原子态粒子(N⁺,N)的产生率和氮化粒子(N⁺,N_f)轰击靶表面的能量、粒子数密度及入射角分布随气体温度的变化规律.结果表明,使阴极靶处活性粒子(N⁺,N_f)的能量高且粒子数密度大,存在一个最佳放电温度;粒子(N⁺,N)的产生率及在靶表面的密度数都随着放电气体温度的升高而减少;有大量中性快原子N_f在工件表面小角入射,且粒子(N⁺,N_f)角分布受温度的影响很小.     

From self-assembly to quantum guiding: A review of magnetic atomic structures on noble metal surfaces

Recent advances in the study of magnetic atomic structures on noble metal surfaces are reviewed. These include one- dimensional strings, two-dimensional hexagonal superlattices, and novel structures stabilized by quantum guiding. The combined techniques of low-temperature scanning tunneling microscopy, kinetic Monte Carlo simulations, and ab initio calculations reveal that surface-state-mediated adatom-step and adatom-adatom interactions are the driving forces for self- assembly of these structures. The formation conditions are further discussed by comparing various experimental systems and the kinetic Monte Carlo simulations. Using scanning tunneling spectroscopy and tight-binding calculations together, we reveal that the spectra of these well-ordered structures have characteristic peaks induced by electronic scattering processes of the atoms within the local environment. Moreover, it is demonstrated that quantum confinement by means of nano-size corrals has significant influence on adatom diffusion and self-assembly, leading to a quantum-guided self-assembly.