What are the advantages and disadvantages of electron microscopes
advantage:
1. High resolution. The resolution of the optical microscope is 0.2μm, and the resolution of the transmission electron microscope is 0.2nm. That is to say, the transmission electron microscope is magnified 1000 times based on the optical microscope.
2. Transmission electron microscopes are often used to observe minute material structures that cannot be distinguished with ordinary microscopes; scanning electron microscopes are mainly used to observe the morphology of solid surfaces, and can also be combined with X-ray diffractometers or electron energy spectrometers. It constitutes an electron microprobe for material composition analysis; an emission electron microscope is used for the study of self-emitting electron surfaces.
shortcoming:
1. In an electron microscope, the sample must be observed in a vacuum, so living samples cannot be observed. With the advancement of technology, environmental scanning electron microscopy will gradually enable direct observation of living samples;
2. When processing the sample, structures that the sample does not originally have may be produced, which makes it more difficult to analyze the image later;
3. Due to the extremely strong electron scattering ability, secondary diffraction is prone to occur;
4. Because it is a two-dimensional plane projection image of a three-dimensional object, sometimes the image is not unique;
5. Since transmission electron microscopes can only observe very thin samples, the structure of the surface of the substance may be different from the structure of the interior of the substance;
6. For ultra-thin samples (below 100 nanometers), the sample preparation process is complex and difficult, and the sample preparation may be damaged;
7. The electron beam may destroy the sample through collision and heating;
8. In addition, the purchase and maintenance prices of electron microscopes are relatively high.
