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首页> 外文期刊>Physical review >Noncontact atomic force microscopy imaging of atomic structure and cation defects of the polar MgAl_2O_4 (100) surface: Experiments and first-principles simulations
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Noncontact atomic force microscopy imaging of atomic structure and cation defects of the polar MgAl_2O_4 (100) surface: Experiments and first-principles simulations

机译：MgAl_2O_4（100）极性表面的原子结构和阳离子缺陷的非接触原子力显微镜成像：实验和第一性原理模拟

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摘要

Atom-resolved noncontact atomic force microscopy (NC-AFM) was recently used to reveal that the insulating spinel MgAl_2O_4(100) surface, when prepared under vacuum conditions, adopts a structurally well-defined Al and O-rich structure (Al_4-O_4-Al_4 termination) consisting of alternating Al and double-0 rows, which are, however, interrupted by defects identified as interchanged Mg in the surface layers (so-called antisite defects). From an interplay of futher NC-AFM experiments and first-principles NC-AFM image simulations, we present here a detailed analysis of the NC-AFM contrast on the MgAl_2O_4(100) surface. Experiments show that the contrast on MgAl_2O_4(100) in atom-resolved NC-AFM is dominated by two distinctly different types of contrast modes, reflecting two oppositely charged tip-apex terminations. In this paper, we analyze the contrast associated with these imaging modes and show that a positively charged tip-apex (presumably Mg~(2+)) interacts most strongly with the oxygen atoms, thus imaging the oxygen lattice, whereas a negatively charged tip-apex (O~(2-)) will reveal the cation sublattice on MgAl_2O_4 The analysis of force-vs-distance calculations for the two tips shows that this qualitative picture, developed in our previous study, holds for all realistic tip-surface imaging parameters, but the detailed resolution on the O double rows and Al rows changes as a function of tip-surface distance, which is also observed experimentally. We also provide an analysis of the tip dependency and tip-surface distance dependency for the NC-AFM contrast associated with single Al vacancies and Mg-Al antisite defects on the MgAl_2O_4(100) surface and show that it is possible on the basis of NC-AFM image simulations to discriminate between the Al~(3+) and Mg~(2+) species in antisite defects and hypothetical Al vacancies.
机译：最近使用原子分辨非接触原子力显微镜（NC-AFM）揭示了绝缘尖晶石MgAl_2O_4（100）表面在真空条件下制备时采用结构明确的Al和O富结构（Al_4-O_4- Al_4端接）由交替的Al和双0行组成，但是被表层中标识为Mg互换的缺陷（所谓的反位缺陷）打断。通过进一步的NC-AFM实验与第一原理NC-AFM图像模拟的相互作用，我们在此介绍MgAl_2O_4（100）表面上NC-AFM对比度的详细分析。实验表明，在原子分辨的NC-AFM中，MgAl_2O_4（100）上的对比度受两种截然不同类型的对比度模式的支配，反映出两个带相反电荷的尖端-末端终止。在本文中，我们分析了与这些成像模式相关的对比度，并发现带正电荷的尖端（大概是Mg〜（2+））与氧原子相互作用最强，从而成像了氧晶格，而带负电的尖端-顶点（O〜（2-））将揭示MgAl_2O_4上的阳离子亚晶格。对两个尖端的力-视距计算的分析表明，在我们先前的研究中开发的这张定性图片适用于所有现实的尖端表面成像参数，但O双排和Al双排的详细分辨率会根据刀尖表面距离而变化，这也可以通过实验观察到。我们还分析了与MgAl_2O_4（100）表面上的单个Al空位和Mg-Al反位缺陷相关的NC-AFM对比的尖端依赖性和尖端表面距离依赖性，并表明有可能在NC的基础上-AFM图像模拟以区分反位缺陷和假设的Al空位中的Al〜（3+）和Mg〜（2+）物种。

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  • 来源
    《Physical review》 |2011年第23期|p.235419.1-235419.14|共14页
  • 作者

    Morten K. Rasmussen; Adam S. Foster; Filippo F. Canova; Berit Hinnemann; Stig Helveg; Kristoffer Meinander; Flemming Besenbacher; Jeppe V. Lauritsen;

  • 作者单位

    Interdisciplinary Nanoscience Center (iNANO), University of Aarhus, Denmark;

    Department of Physics, Tampere University of Technology, Finland,Department of Applied Physics, Aalto University School of Science, Finland;

    Department of Physics, Tampere University of Technology, Finland,Department of Applied Physics, Aalto University School of Science, Finland;

    Haldor Tops0e A/S, Nym0llevej 55, 2800 Kongens Lyngby, Denmark;

    Haldor Tops0e A/S, Nym0llevej 55, 2800 Kongens Lyngby, Denmark;

    Interdisciplinary Nanoscience Center (iNANO), University of Aarhus, Denmark;

    Interdisciplinary Nanoscience Center (iNANO), University of Aarhus, Denmark;

    Interdisciplinary Nanoscience Center (iNANO), University of Aarhus, Denmark;

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  • 正文语种 eng
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  • 关键词

    oxide surfaces; atomic force microscopy (AFM);

    机译：氧化物表面原子力显微镜（AFM）;

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