Drab Marek, Krajniak Janusz, Grzelakowski Krzysztof P
1USI,Unit of Nanostructural Bio-Interactions,Institute of Immunology and Experimental Therapy,Polish Academy of Sciences,Weigla 12 Street,53-114 Wroclaw,Poland.
2Laboratory of Isotope Geology and Geoecology,Department of Applied Geology,Geochemistry and Environmental Management,Institute of Geological Sciences,University of Wroclaw,Cybulskiego 30,50-205 Wrocław,Poland.
Microsc Microanal. 2016 Dec;22(6):1369-1373. doi: 10.1017/S1431927616012514. Epub 2016 Dec 15.
We report on a robust method for chemical element-sensitive imaging by scanning electron microscopy (SEM). The commercial Auriga FE-SEM microscope (Carl Zeiss, Oberkochen, Germany), equipped with an energy-selective grid detector (EsB) as a part of the experimental setup, was applied for generation of chemical contrast at low accelerating voltages, which is gentle for sensitive samples. The EsB-grid detector, conceptually adapted by us as an energy retarding field analyzer (RFA), was used to detect the two-dimensional (2D) energy spectrum for the first time. The electron energy spectrum measured by sweeping the retarding grid potential revealed thresholds corresponding to electronic transitions in the specimen, followed by 2D-derivation treatment applied just at the observed thresholds. This allowed chemical mapping by SEM. In this report the 273 eV Auger transition in carbon deposited onto the Si(100) sample was chosen as a source for chemical contrast in the SEM image. In addition to Auger electrons, we expect analogous energy-selective contrast enhancement for inelastically scattered electrons, for example, in plasmonic contrast and elastically scattered electrons, for example in phase contrast, our method, proved for carbon, is expected to apply to a broader list of elements as a general capability of chemical mapping, at several-fold better lateral resolution when compared with energy dispersive spectroscopy (EDS).
我们报道了一种通过扫描电子显微镜（SEM）进行化学元素敏感成像的稳健方法。将配备能量选择性栅极探测器（EsB）作为实验装置一部分的商用奥里加场发射扫描电子显微镜（Carl Zeiss，德国奥伯科亨）用于在低加速电压下生成化学对比度，这对敏感样品较为温和。我们从概念上将EsB栅极探测器改编为能量减速场分析仪（RFA），首次用于检测二维（2D）能谱。通过扫描减速栅极电位测量的电子能谱揭示了与样品中电子跃迁相对应的阈值，随后仅在观察到的阈值处进行二维推导处理。这使得能够通过SEM进行化学映射。在本报告中，选择沉积在Si(100)样品上的碳中的273 eV俄歇跃迁作为SEM图像中化学对比度的来源。除了俄歇电子外，我们预计对于非弹性散射电子（例如等离子体对比度）和弹性散射电子（例如相位对比度）也会有类似的能量选择性对比度增强，我们针对碳验证的方法有望作为化学映射的一般能力应用于更广泛的元素列表，与能量色散谱（EDS）相比，横向分辨率提高几倍。
