Difference Between Electron Microscope, Atomic Force Microscope, Scanning Tunneling Microscope
Electron microscope, atomic force microscope, scanning tunneling microscope. The difference:
one. Compared with optical microscopes and transmission electron microscopes, scanning electron microscopes have the following characteristics:
(1) The structure of the surface 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 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-dimensional effect. The depth of field of a scanning electron microscope is hundreds of times larger than that of an optical microscope, and dozens of times larger than that of a transmission electron microscope.
(5) The magnification range of the image is wide and the resolution is relatively high. It can be magnified from 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 the optical microscope and the transmission electron microscope, up to 3nm.
(6) The damage and contamination of the sample by the electron beam is small.
(7) While observing the morphology, other signals from the sample can also be used for micro-area composition 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 force between the surface of the sample to be tested and a miniature force-sensitive element. One end of a pair of extremely sensitive micro-cantilevers is fixed, and the micro-tip at the other end is close to the sample. At this time, it will interact with it, and the force will cause the micro-cantilever to deform or change its motion state. When the sample is scanned, the sensor is used to detect these changes, and the force distribution information can be obtained, so that the surface topography structure information and surface roughness information can be obtained with nanometer resolution.
Compared with scanning electron microscopes, atomic force microscopes have many advantages. Unlike electron microscopes, which can only provide two-dimensional images, AFMs provide true three-dimensional surface maps. At the same time, AFM does not require any special treatment of the sample, such as copper plating or carbon, which can cause irreversible damage to the sample. Third, electron microscopes need to operate under high vacuum conditions, and 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, 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 microscopy has atomic-level spatial resolution, with a lateral spatial resolution of 1 and a longitudinal resolution of 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 microscopy can detect the structure of matter in vacuum, atmospheric pressure, air, and even solution. Because there is no high-energy electron beam, there is no damage to the surface (such as radiation, thermal damage, etc.), so the structure of biological macromolecules and living cell membrane surfaces under physiological conditions can be studied, and the samples will not be damaged and remain intact.
④ The scanning speed of scanning tunneling microscope is fast, the time for data acquisition is short, and the imaging is also fast, and it is possible to carry out kinetic studies of life processes.
⑤ It does not need any lens and is small in size. Some people call it a "pocket microscope".
