Schweizer Peter, Denninger Peter, Dolle Christian, Spiecker Erdmann
Institute of Micro- and Nanostructure Research and Center for Nanoanalysis and Electron Microscopy (CENEM), FAU Erlangen-Nürnberg, Cauerstraße 3, 91058 Erlangen, Germany.
Institute of Micro- and Nanostructure Research and Center for Nanoanalysis and Electron Microscopy (CENEM), FAU Erlangen-Nürnberg, Cauerstraße 3, 91058 Erlangen, Germany; Instituto de Ciencia Molecular, Universitat de València, Catedrático José Beltrán Martínez 2, 46980 Paterna, Spain.
Ultramicroscopy. 2020 Jun;213:112956. doi: 10.1016/j.ultramic.2020.112956. Epub 2020 Feb 4.
Electron diffraction is a powerful characterization method that is used across different fields and in different instruments. In particular, the power of transmission electron microscopy (TEM) largely relies on the capability to switch between imaging and diffraction mode enabling identification of crystalline phases and in-depth studies of crystal defects, to name only examples. In contrast, while diffraction techniques have found their way into the realm of scanning electron microscopy (SEM) in the form of electron backscatter diffraction and related techniques, on-axis transmission diffraction is still in its infancy. Here we present a simple but versatile setup that enables a 'diffraction mode' in SEM using a fluorescent screen and a dedicated in vacuo camera. With this setup spot-like nano-beam diffraction patterns of thin samples can be acquired with electron energies as low as 500 eV. We therefore coin the name Low Energy Nano Diffraction (LEND). Diffraction patterns can be recorded from single positions on the sample or integrated over selected areas by adjustable scan patterns. Besides showing the principal application of the technique to standard materials such as gold and silicon we also explore the application to graphene and other 2D materials. Besides single pattern measurements, also full 4D-STEM diffraction mappings are demonstrated. Finally, we show how the integration of a versatile diffraction mode in SEM enables a thorough analysis performed with a single instrument.
电子衍射是一种强大的表征方法，在不同领域和不同仪器中都有应用。特别是，透射电子显微镜（TEM）的强大功能很大程度上依赖于在成像和衍射模式之间切换的能力，从而能够识别晶相并深入研究晶体缺陷，仅举这些例子。相比之下，虽然衍射技术已经以电子背散射衍射及相关技术的形式进入扫描电子显微镜（SEM）领域，但轴上透射衍射仍处于起步阶段。在此，我们展示了一种简单但通用的装置，该装置利用荧光屏和专用的真空相机在SEM中实现了“衍射模式”。通过这种装置，对于薄样品，可在低至500电子伏特的电子能量下获取点状纳米束衍射图案。因此，我们将其命名为低能纳米衍射（LEND）。衍射图案可以从样品上的单个位置记录，也可以通过可调扫描图案在选定区域上进行积分。除了展示该技术在金和硅等标准材料上的主要应用外，我们还探索了其在石墨烯和其他二维材料上的应用。除了单图案测量外，还展示了完整的4D-STEM衍射映射。最后，我们展示了SEM中通用衍射模式的集成如何能够使用单一仪器进行全面分析。
