Yoon Aram, Herzog Antonia, Grosse Philipp, Alsem Daan Hein, Chee See Wee, Roldán Cuenya Beatriz
Department of Interface Science, Fritz-Haber-Institute of the Max-Planck Society, Berlin, Germany.
Hummingbird Scientific, Lacey, WA98516, USA.
Microsc Microanal. 2021 Feb;27(1):121-128. doi: 10.1017/S1431927620024769.
The development of microfabricated liquid cells has enabled dynamic studies of nanostructures within a liquid environment with electron microscopy. While such setups are most commonly found in transmission electron microscope (TEM) holders, their implementation in a scanning electron microscope (SEM) offers intriguing potential for multi-modal studies where the large chamber volume allows for the integration of multiple detectors. Here, we describe an electrochemical liquid cell SEM platform that employs the same cells enclosed by silicon nitride membrane windows found in liquid cell TEM holders and demonstrate the imaging of copper oxide nanoparticles in solution using both backscattered and transmitted electrons. In particular, the transmitted electron images collected at high scattering angles show contrast inversion at liquid layer thicknesses of several hundred nanometers, which can be used to determine the presence of liquid in the cell, while maintaining enough resolution to image nanoparticles that are tens of nanometers in size. Using Monte Carlo simulations, we show that both imaging modes have their advantages for liquid phase imaging and rationalize the contrast inversion observed in the transmitted electron image.
微纳加工液体池的发展使得利用电子显微镜对液体环境中的纳米结构进行动态研究成为可能。虽然这种装置最常见于透射电子显微镜（TEM）样品台中，但将其应用于扫描电子显微镜（SEM）可为多模态研究提供有趣的潜力，因为大腔室体积允许集成多个探测器。在此，我们描述了一种电化学液体池SEM平台，该平台采用与液体池TEM样品台中相同的由氮化硅膜窗口包围的液体池，并展示了使用背散射电子和透射电子对溶液中的氧化铜纳米颗粒进行成像。特别是，在高散射角收集的透射电子图像在几百纳米的液层厚度处显示出对比度反转，这可用于确定池中液体的存在，同时保持足够的分辨率以对尺寸为几十纳米的纳米颗粒进行成像。通过蒙特卡罗模拟，我们表明两种成像模式在液相成像方面都有其优势，并对透射电子图像中观察到的对比度反转进行了合理说明。
