Surface, subsurface and buried interface structure at the atomic scale; pushing the limits of medium energy ion scattering

固体表面在许多实际情况下都很重要，例如多相催化，腐蚀以及一种固体与另一种固体结合以制造电子设备的方式。通常只是固体最外层的一个或两个原子层决定了这些性质，在过去的30年里，已经开发了一系列专门的技术，这些技术只探测这几个层，而不受下面的散装固体的影响，对于这些固体，存在一系列其他分析方法。中能离子散射（MEIS）在弥合这些方法之间的差距方面本质上是独特的;它可以用于探测最外面的几个原子层，但也可以探测表面以下多达几百个原子层的次表面。在这些深度尺度上，它可以提供成分和结构的信息，并具有不寻常的优势是特别敏感的固体表面如何可能被修改的存在下吸附的原子和molecular.This项目旨在利用这些特殊的优势，使用英国国家MEIS设施在达雷斯伯里，调查模型系统，代表了一些不同的表面和近表面的系统和现象。一个例子是氧化物表面的问题，在多相催化中非常重要，但相对未被探索，特别是在其表面结构方面。金属上的超薄氧化膜与其应用特别相关，MEIS将用于确定特定系统中的氧化物表面和氧化物/金属界面结构，特别是Pd（111）/V2 O3。已知表面的反应性通常受到表面缺陷（如原子台阶）的强烈影响，但缺乏有关这些台阶结构和原子在还原配位位点松弛方式的详细信息;计划进行MEIS调查以解决这一问题。该技术也非常适合于研究由吸附的分子引起的金属表面的扭曲，并建议利用这一点来探测硫醇/金属界面，特别是;这些形成了许多自组装单层的基础，但界面结构知之甚少。最后，MEIS提供的结构和成分信息的组合在研究金属合金表面和表面合金的表面和近表面性质方面具有重要价值，并提出了这种类型的特定模型系统用于研究，包括磁性感兴趣的系统。拟议研究的进一步主题涉及MEIS技术本身的基础物理研究，特别是非弹性能量损失的性质，其赋予MEIS其深度分辨率，以及中和作用，其影响离子产率并因此影响定量。更好地了解这些过程应该有利于整个MEIS用户社区，允许更详细和更可靠的信息，从MEIS实验提取。

Solid surfaces are important in many practical situations, such as heterogeneous catalysis, corrosion and the way one solid bonds to another to make electronic devices. Often it is just the outermost one or two atomic layers of the solid which determine these properties, and over the last 30 years a range of specialised techniques have been developed which probe only these few layers and are not influenced by the underlying bulk solid for which a range of other analytical methods exist. Medium energy ion scattering (MEIS) is essentially unique in bridging the gap between these sets of methods; it can be used to probe only the outermost few atomic layers, but can also probe the subsurface up to a few hundred atomic layers below the surface. On these depth scales it can provide both compositional and structural information, and has the unusual advantage of being especially sensitive to how a solid surface may be modified by the presence of adsorbed atoms and molecules.This project seeks to exploit these special advantages, using the UK national MEIS facility at Daresbury, to investigate model systems which typify a number of different surface and near-surface systems and phenomena. One example is the problem of oxide surfaces, of great importance in heterogeneous catalysis but relatively unexplored, especially in terms of their surface structure. Ultra-thin oxide films on metals are especially relevant to their applications, and MEIS will be used to determine both the oxide surface and oxide/metal interface structure in specific systems, notably Pd(111)/V2O3. The reactivity of surfaces is known to often be strongly influenced by surface defects, such as atomic steps, yet detailed information on the structure of these steps and the way the atoms relax at the reduced coordination sites is lacking; MEIS investigations are planned to address this problem. The technique is also ideally suited to investigate distortions of a metal surface induced by adsorbed molecules, and it is proposed to exploit this to probe thiol/metal interfaces, in particular; these form the basis of many self-assembled monolayers, yet the interface structure is poorly understood. Finally, the combination of structural and compositional information provided by MEIS is of great value in studying the surface and near-surface properties of metal alloy surfaces and surface alloys, and specific model systems of this type are proposed for study, including systems of interest in magnetism.A further theme of the proposed research involves investigations of the fundamental physics of the MEIS technique itself, notably the nature of inelastic energy loss, which gives MEIS its depth resolution, and neutralisation, which influences the ion yields and thus the quantification. A better understanding of these processes should benefit the whole MEIS user community, allowing more detailed and more reliable information to be extracted from MEIS experiments.