Preliminary Results from the First Monochromated and Aberration Corrected 200-kV Field-Emission Scanning Transmission Electron Microscope
Preliminary Results from the First Monochromated and Aberration Corrected 200-kV Field-Emission Scanning Transmission Electron Microscope
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第一台单色和像差校正 200 kV 场发射扫描透射电子显微镜的初步结果
DOI：
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发表时间：
2006
影响因子：
2.8
通讯作者：
H. Stegmann
中科院分区：
文献类型：
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作者：
T. Walther;H. Stegmann
本文介绍了第一台工作在200kV的单色校正扫描电子显微镜的实验结果。描述了直径小于0.2 nm、能量宽度明显低于0.3 eV的电子探针的形成及其在材料科学中纳米级结构化学分析中的计划应用。能量和空间分辨率都将从中受益：单色仪提高了研究边缘结构附近能量损失的能量分辨率。Cs校正器允许对于给定的束流形成较小的探头，或者在固定的探头大小下使用较大的聚光器孔径产生增强的束流密度。我们还指出了这两种组件组合的另一个优点：在像差校正仪器中使用较大的聚光器孔径来增加会聚角度将会扩大不希望看到的色散。这反过来又会影响空间分辨率。多色探头尾部的影响与会聚角、色差常数和能量分布的乘积成正比。因此，在我们的新仪器中，可以通过将能量宽度减小相同的系数来补偿它，因为增加了光束的会聚以形成更强的探测器。在未来的发展中，另一种选择可能是对色差进行硬件校正，从而完全消除色度探针的扩散。
Experimental results from the first monochromated and aberration-corrected scanning transmission electron microscope operated at 200 kV are described. The formation of an electron probe with a diameter of less than 0.2 nm at an energy width significantly under 0.3 eV and its planned application to the chemical analysis of nanometer-scale structures in materials science are described. Both energy and spatial resolution will benefit from this: The monochromator improves the energy resolution for studies of energy loss near edge structures. The Cs corrector allows formation of either a smaller probe for a given beam current or yields, at fixed probe size, an enhanced beam current density using a larger condenser aperture. We also point out another advantage of the combination of both components: Increasing the convergence angle by using larger condenser apertures in an aberration-corrected instrument will enlarge the undesirable chromatic focus spread. This in turn influences spatial resolution. The effect of polychromatic probe tails is proportional to the product of convergence angle, chromatic aberration constant, and energy spread. It can thus be compensated for in our new instrument by decreasing the energy width by the same factor as the beam convergence is increased to form a more intense probe. An alternative in future developments might be hardware correction of the chromatic aberration, which could eliminate the chromatic probe spread completely.