The difference between electron microscope, atomic force microscope and scanning tunneling microscope
one. Characteristics of scanning electron microscope Compared with optical microscope and transmission electron microscope, scanning electron microscope has the following characteristics:
(1) The surface structure of the sample can be directly observed, and the size of the sample can be as large as 120mm×80mm×50mm.
(2) The sample preparation process is simple and does not need to be cut into thin slices.
(3) The sample can be translated and rotated in a three-dimensional space in the sample chamber, so the sample can be observed from various angles.
(4) The depth of field is large, and the image is full of three-dimensionality. The depth of field of the scanning electron microscope is hundreds of times larger than that of the optical microscope and dozens of times larger than that of the transmission electron microscope.
(5) The magnification range of the image is wide and the resolution is relatively high. It can be magnified ten times to hundreds of thousands of times, and it basically includes the magnification range from magnifying glass, optical microscope to transmission electron microscope. The resolution is between optical microscope and transmission electron microscope, up to 3nm.
(6) The damage and contamination of the sample by the electron beam are relatively small.
(7) While observing the morphology, other signals from the sample can also be used for micro-component analysis.
2. Atomic Force Microscope
Atomic Force Microscope (AFM), an analytical instrument that can be used to study the surface structure of solid materials, including insulators. It studies the surface structure and properties of substances by detecting the extremely weak interatomic interaction between the surface of the sample to be tested and a miniature force-sensitive element. One end of a pair of microcantilever sensitive to weak force is fixed, and the tiny tip of the other end is close to the sample. At this time, it will interact with it, and the force will make the microcantilever deform or change its motion state. When scanning the sample, use the sensor to detect these changes, and the force distribution information can be obtained, so as to obtain the surface topography structure information and surface roughness information with nanometer resolution.
Atomic force microscopy has many advantages over scanning electron microscopy. Unlike electron microscopes, which only provide two-dimensional images, AFMs provide true three-dimensional maps of surfaces. At the same time, AFM does not require any special treatment of the sample, such as copper plating or carbon plating, which can cause irreversible damage to the sample. Third, electron microscopes need to operate under high vacuum conditions, while atomic force microscopes can work well under normal pressure and even in liquid environments. This can be used to study biological macromolecules and even living biological tissues. Compared with scanning tunneling microscope (Scanning Tunneling Microscope), atomic force microscope has wider applicability because it can observe non-conductive samples. The scanning force microscope, which is widely used in scientific research and industry, is based on the atomic force microscope.
3. Scanning tunneling microscope
① High resolution Scanning tunneling microscope has atomic-level spatial resolution, its lateral spatial resolution is 1, and its longitudinal resolution is 0.1.
② The scanning tunneling microscope can directly detect the surface structure of the sample, and can draw a three-dimensional structure image.
③ Scanning tunneling microscope can detect the structure of matter in vacuum, atmospheric pressure, air, and even solution. Since there is no high-energy electron beam, there is no destructive effect on the surface (such as radiation, heat damage, etc.), so it can study the structure of biological macromolecules and living cell membrane surfaces under physiological conditions, and the samples will not be damaged and remain intact.
④ The scanning speed of the scanning tunneling microscope is fast, the time for obtaining data is short, and the imaging is also fast, so it is possible to carry out dynamic research on life processes.
⑤ It does not need any lens and is small in size. Some people call it "pocket microscope".
