Gauquelin N, van den Bos K H W, Béché A, Krause F F, Lobato I, Lazar S, Rosenauer A, Van Aert S, Verbeeck J
Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
Ultramicroscopy. 2017 Oct;181:178-190. doi: 10.1016/j.ultramic.2017.06.002. Epub 2017 Jun 3.
Nowadays, aberration corrected transmission electron microscopy (TEM) is a popular method to characterise nanomaterials at the atomic scale. Here, atomically resolved images of nanomaterials are acquired, where the contrast depends on the illumination, imaging and detector conditions of the microscope. Visualization of light elements is possible when using low angle annular dark field (LAADF) STEM, annular bright field (ABF) STEM, integrated differential phase contrast (iDPC) STEM, negative spherical aberration imaging (NCSI) and imaging STEM (ISTEM). In this work, images of a NdGaO-LaSrMnO (NGO-LSMO) interface are quantitatively evaluated by using statistical parameter estimation theory. For imaging light elements, all techniques are providing reliable results, while the techniques based on interference contrast, NCSI and ISTEM, are less robust in terms of accuracy for extracting heavy column locations. In term of precision, sample drift and scan distortions mainly limits the STEM based techniques as compared to NCSI. Post processing techniques can, however, partially compensate for this. In order to provide an outlook to the future, simulated images of NGO, in which the unavoidable presence of Poisson noise is taken into account, are used to determine the ultimate precision. In this future counting noise limited scenario, NCSI and ISTEM imaging will provide more precise values as compared to the other techniques, which can be related to the mechanisms behind the image recording.
如今，像差校正透射电子显微镜（TEM）是一种在原子尺度上表征纳米材料的常用方法。在此，可获取纳米材料的原子分辨图像，其对比度取决于显微镜的照明、成像和探测器条件。使用低角度环形暗场（LAADF）扫描透射电子显微镜（STEM）、环形亮场（ABF）STEM、积分差分相衬（iDPC）STEM、负球差成像（NCSI）和成像STEM（ISTEM）时，可以实现轻元素的可视化。在这项工作中，通过使用统计参数估计理论对钕镓酸盐-镧锶锰氧化物（NGO-LSMO）界面的图像进行了定量评估。对于轻元素成像，所有技术都能提供可靠的结果，而基于干涉衬度的技术、NCSI和ISTEM在提取重原子列位置的准确性方面则不够稳健。在精度方面，与NCSI相比，样品漂移和扫描畸变主要限制了基于STEM的技术。不过，后处理技术可以部分弥补这一点。为了展望未来，考虑到不可避免存在的泊松噪声的NGO模拟图像被用于确定最终精度。在这种未来计数噪声受限的情况下，与其他技术相比，NCSI和ISTEM成像将提供更精确的值，这可能与图像记录背后的机制有关。
