Transmission electron microscopy at very low energy is a promising way to avoid damaging delicate biological samples with the incident electrons, a known problem in conventional transmission electron microscopy. For imaging in the 0-30 eV range, we added a second electron source to a low energy electron microscopy (LEEM) setup, enabling imaging and spectroscopy in both transmission and reflection mode at nanometer (nm) resolution. The latter is experimentally demonstrated for free-standing graphene. Exemplary eV-TEM micrographs of gold nanoparticles suspended on graphene and of DNA origami rectangles on graphene oxide further establish the capabilities of the technique. The long and short axes of the DNA origami rectangles are discernable even after an hour of illumination with low energy electrons. In combination with recent developments in 2D membranes, allowing for versatile sample preparation, eV-TEM is paving the way to damage-free imaging of biological samples at nm resolution.

中文翻译：

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用于成像和光谱的互补 LEEM 和 eV-TEM

非常低能量的透射电子显微镜是一种很有前途的方法，可以避免入射电子损坏脆弱的生物样品，这是传统透射电子显微镜中的一个已知问题。对于 0-30 eV 范围内的成像，我们在低能电子显微镜 (LEEM) 设置中添加了第二个电子源，以纳米 (nm) 分辨率在透射和反射模式下进行成像和光谱分析。后者通过实验证明用于独立的石墨烯。悬浮在石墨烯上的金纳米颗粒和氧化石墨烯上的 DNA 折纸矩形的示例性 eV-TEM 显微照片进一步证实了该技术的能力。即使在低能电子照射一小时后，DNA 折纸矩形的长轴和短轴仍可辨别。