Beyer André, Vieker Henning, Klett Robin, Meyer Zu Theenhausen Hanno, Angelova Polina, Gölzhäuser Armin
Physics of Supramolecular Systems and Surfaces, Bielefeld University, 33615 Bielefeld, Germany.
CNM Technologies GmbH, 33609 Bielefeld, Germany.
Beilstein J Nanotechnol. 2015 Aug 12;6:1712-20. doi: 10.3762/bjnano.6.175. eCollection 2015.
Carbon nanomembranes (CNMs) prepared from aromatic self-assembled monolayers constitute a recently developed class of 2D materials. They are made by a combination of self-assembly, radiation-induced cross-linking and the detachment of the cross-linked SAM from its substrate. CNMs can be deposited on arbitrary substrates, including holey and perforated ones, as well as on metallic (transmission electron microscopy) grids. Therewith, freestanding membranes with a thickness of 1 nm and macroscopic lateral dimensions can be prepared. Although free-standing CNMs cannot be imaged by light microscopy, charged particle techniques can visualize them. However, CNMs are electrically insulating, which makes them sensitive to charging. We demonstrate that the helium ion microscope (HIM) is a good candidate for imaging freestanding CNMs due to its efficient charge compensation tool. Scanning with a beam of helium ions while recording the emitted secondary electrons generates the HIM images. The advantages of HIM are high resolution, high surface sensitivity and large depth of field. The effects of sample charging, imaging of multilayer CNMs as well as imaging artefacts are discussed.
由芳香族自组装单分子层制备的碳纳米膜（CNM）是最近开发的一类二维材料。它们是通过自组装、辐射诱导交联以及交联的自组装单分子层与其基底分离相结合的方法制成的。碳纳米膜可以沉积在任意基底上，包括有孔和穿孔的基底，以及金属（透射电子显微镜）网格上。由此，可以制备出厚度为1纳米且具有宏观横向尺寸的独立膜。尽管独立的碳纳米膜无法通过光学显微镜成像，但带电粒子技术可以使其可视化。然而，碳纳米膜是电绝缘的，这使得它们对充电敏感。我们证明，由于其高效的电荷补偿工具，氦离子显微镜（HIM）是对独立碳纳米膜成像的良好候选设备。在记录发射的二次电子的同时用一束氦离子进行扫描，生成氦离子显微镜图像。氦离子显微镜的优点是分辨率高、表面灵敏度高和景深大。讨论了样品充电的影响、多层碳纳米膜的成像以及成像伪像。
