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电子显微镜是一类高功率显微镜技术，它们使用电子而不是光子对表面进行成像。它们通常被称为超级分辨率显微镜作为分辨率，并且能够成像小物体和材料，远大于光学显微镜技术的能力。欧洲杯足球竞彩尽管所有电子显微镜技术都使用电子，但内部工作因技术而异。在本文中，我们研究了最常见的电子显微镜技术如何工作。
扫描电子显微镜（SEM）
SEM is one of the most widely used electron microscopy techniques and its use is growing across many scientific fields. In SEM, an electron gun fires a beam of high energy electrons towards a sample. The electrons are controlled, directed and accelerated using a series of optical components, including lenses, scanning coils, deflector plates and an aperture.
The electrons then interact with the surface of the sample, causing the sample to emit secondary Auger electrons and X-rays. The primary electrons which interact with the sample are also backscattered. When the electrons interact with the sample, they quickly lose energy through elastic scattering and absorption mechanisms and this energy exchange causes the primary electrons to backscatter off the surface. Detectors are used to measure both types of electrons and the X-rays to build up an image of the sample.
样品的图像是通过测量这些表面相互作用产生的信号的强度来构建的。发射的X射线具有针对每个元素的特定特征，这可以确定表面的元素组成。阴极发光也可以集成到SEM成像模式中，以确定样品的多重结构（在原子水平上）和电性能，以及材料表面上是否存在任何污染。
透射电子显微镜（TEM）
TEM在许多方面都与SEM相似，尤其是在使用电子枪向样品向高能电子发射的情况下，使用一系列光学组件加速和聚焦电子。TEM是另一种广泛使用的电子显微镜技术，近年来作为一种有效的成像技术也获得了很多吸引力。
但是，SEM和TEM之间存在一些差异。如果SEM关注发射电子并测量它们与样品相互作用时的散射方式，则TEM中的电子通过材料，并且不会被样品拼凑而成。一些电子仍然分散，但未在常规TEM成像模式下测量（有关更多详细信息，请参见下面的REM模式）。
This operating principle makes TEM a useful imaging technique for thinner materials. The actual working principles are very similar to optical microscopy, where photons pass through a sample to generate an image. However, in the case of TEM, it is the transmission of the electrons through the material that relays information about the sample, which are then magnified by an objective lens to produce the image. Overall, as well as an image of the sample, TEM can be used to provide information on a sample’s crystal structure, morphology and surface stress state.
反射电子显微镜（REM）
REM是TEM的变体，其中测量了反射的电子光束，而不是传输光束。尽管TEM测量通过样品的电子，但某些电子是反向散射的，并且该模式可用于测量这些电子。这是一种与TEM一起使用的成像模式，但并未在其他电子显微镜方法中广泛使用，并且当它通常与各种光谱技术结合时，以完全表征样品。然而，它有用于测量晶体样品的平坦面，可用于给出样品表面的高分辨率，因为只有样品的前几个原子层与这些反向散射相互作用有关。
Sources and Further Reading
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