DIFFRACTION AND HOLOGRAPHY WITH PHOTOELECTRONS AND AUGER ELECTRONS - SOME NEW DIRECTIONS
DIFFRACTION AND HOLOGRAPHY WITH PHOTOELECTRONS AND AUGER ELECTRONS - SOME NEW DIRECTIONS
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DOI：
10.1016/0167-5729(93)90012-e
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发表时间：
1993-01-01
影响因子：
9.8
通讯作者：
FADLEY, CS
中科院分区：
文献类型：
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作者：
FADLEY, CS
回顾了光电子和俄歇电子衍射的现状，重点介绍了新的活动方向。在吸附分子、外延层和清洁表面的研究中使用前向散射是最成熟的应用之一，并且随着更高的能量分辨率和自旋分析用于根据化学态、表面位置或磁性状态来解析发射器，该应用将变得更加强大。使用跨越表面上方相当大一部分立体角的较大数据集也将大大增强可用的结构信息，例如在表面上外延层或纳米结构的生长中。基于单次散射或多次散射的实验数据与理论计算的详细拟合也应提供更丰富的结构信息，包括基底层间弛豫等参数。还可以研究近表面层变得高度无序的表面相变，其结果与低能电子衍射和中能离子散射等技术的结果互补。短程磁序也可以通过以某种方式解决输出电子的自旋来探测，例如通过使用多重分割核心级别。还发现，在涉及的带上存在某种相当完整的积分的情况下，例如通过在更高的光子能量、更高的温度下工作和/或在光谱中对能量进行积分，价态也表现出类核衍射效应。全息分析大规模衍射数据集以直接产生三维原子图像的可能性对于某些类型的问题也很有希望，特别是吸附物或薄覆盖层。尽管这种全息图像会出现几种类型的像差和伪影，但许多校正程序似乎是可能的，并且在模型计算中和几组实验数据中对这些程序进行的测试是令人鼓舞的。尽管这种类型的分析应用于多层基底发射在显示严重拉长的原子图像时仍然存在一些问题，但对于吸附物发射来说不一定如此。最近使用选定数据范围对吸附物进行的实验和理论研究产生了有希望的结果。最后，理论计算表明，将全息方法应用于短程磁序的直接成像也应该是可能的。
The current status of photoelectron and Auger-electron diffraction is reviewed, with emphasis on new directions of activity. The use of forward scattering in the study of adsorbed molecules, epitaxial overlayers, and clean surfaces is one of the most developed applications, and one that will become more powerful as higher energy resolution and perhaps spin analysis are used to resolve emitters on the basis of chemical state, position at a surface, or magnetic state. The use of larger data sets spanning a considerable fraction of the solid angle above a surface will also much enhance the structural information available, for example, in the growth of epitaxial layers or nanostructures on surfaces. Detailed fitting of experimental data to theoretical calculations based upon either single scattering or multiple scattering should also provide more rich structural information, including such parameters as substrate interlayer relaxation. Surface phase transitions in which near-surface layers become highly disordered can also be studied, with results that are complementary to those from such techniques as low-energy electron diffraction and medium-energy ion scattering. Short-range magnetic order also can be probed by somehow resolving the spin of the outgoing electrons, e.g. by using multiplet-split core levels. Valence levels also are found to exhibit core-like diffraction effects in cases for which there is somehow rather complete integration over the bands involved, e.g., through working at higher photon energies, higher temperatures and/or integrating over energy in spectra. The possibility of holographically analyzing large-scale diffraction data sets so as to directly yield three-dimensional atomic images is also promising for certain types of problems, especially adsorbates or thin overlayers. Although several types of aberrations and artifacts arise with such holographic images, a number of correction procedures appear possible, and tests of these in model calculations and for a few sets of experimental data are encouraging. Although the application of this type of analysis to multilayer substrate emission is still somewhat problematic in showing atomic images that are severely elongated, this is not necessarily true for adsorbate emission. A recent experimental and theoretical study of an adsorbate using a selected data range yields promising results. Finally, theoretical calculations indicate that it should also be possible to apply the holographic methodology to the direct imaging of short-range magnetic order.