Persson Axel R, Tornberg Marcus, Sjökvist Robin, Jacobsson Daniel
NanoLund, Lund University, SE-221 00 Lund, Sweden; National Center for High Resolution Electron Microscopy and Centre for Analysis and Synthesis, Lund University, Box 124, SE-221 00 Lund, Sweden.
NanoLund, Lund University, SE-221 00 Lund, Sweden; Solid State Physics, Lund University, Box 118, SE-221 00 Lund, Sweden.
Ultramicroscopy. 2021 Mar;222:113193. doi: 10.1016/j.ultramic.2020.113193. Epub 2021 Jan 1.
In situ studies using transmission electron microscopy (TEM) can provide insights to how properties, structures and compositions of nanostructures are affected and evolving when exerted to heat or chemical exposure. While high-resolved imaging can be obtained continuously, at video-framerates of hundreds of frames per second (fps), compositional analysis struggles with time resolution due to the long acquisition times for a reliable analysis. This especially holds true when performing mapping (correlated spatial and compositional information). Hence, transient changes are difficult to resolve using mapping. In this work, the time-resolution of sequential mapping using scanning TEM (STEM) and energy dispersive spectroscopy (EDS) is improved by acquiring spectrum images during short times and filtering the spectroscopic data. The suggested algorithm uses regularization to smooth and prevent overfitting (known from compressed sensing) to fit model spectra to the data. The algorithm is applied on simulations as well as acquisitions of catalyzed crystal growth (nanowires), performed in situ in a specialized environmental TEM (ETEM). The results show the improved temporal resolution, where the compositional progression of the different regions of the nanostructure is revealed, here with a time-resolution as low as 16 s compared to the minutes usually needed for similar analysis.
使用透射电子显微镜（TEM）进行原位研究，可以深入了解纳米结构的性质、结构和组成在受热或化学暴露时是如何受到影响以及演变的。虽然可以以每秒数百帧（fps）的视频帧率连续获得高分辨率成像，但由于进行可靠分析所需的采集时间较长，成分分析在时间分辨率方面存在困难。在进行映射（相关的空间和成分信息）时尤其如此。因此，使用映射很难解析瞬态变化。在这项工作中，通过在短时间内采集光谱图像并对光谱数据进行滤波，提高了使用扫描透射电子显微镜（STEM）和能量色散光谱（EDS）进行顺序映射的时间分辨率。所提出的算法使用正则化来平滑和防止过拟合（这是压缩感知中已知的），以使模型光谱与数据拟合。该算法应用于模拟以及在专门的环境透射电子显微镜（ETEM）中进行的原位催化晶体生长（纳米线）采集。结果显示了时间分辨率的提高，其中揭示了纳米结构不同区域的成分演变，与通常进行类似分析所需的几分钟相比，这里的时间分辨率低至16秒。
