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Brief Interpretation of Atomic Force Microscopy

Atomic Force Microscope (AFM) is an analytical instrument that can be used to study the surface structure of solid materials including insulators. It fixes one end of a microcantilever that is extremely sensitive to weak force and has a tiny needle tip at the other end to make slight contact with the sample surface. Due to the very weak repulsive force between the atom at the tip of the needle and the atom on the surface of the sample, a small deflection of the cantilever occurs. By detecting the deflection and acting feedback to control the constant repulsion force, the position change of microcantilever corresponding to each point can be obtained, so as to obtain the image of sample surface morphology.

 

Interatomic van der Waals force imaging mode:

 

(1) Contact mode: small distance between the needle tip and the sample surface, using the repulsion force between atoms; high resolution images can be obtained; the sample is deformed and the needle tip is damaged; it is not suitable for materials with soft surface.

 

(2) Non-contact mode: the needle tip is 5—20 nm away from the sample, using the attraction force between atoms, without damaging the sample surface, and samples with a soft surface can be tested; the resolution is low and there is a misinterpretation phenomenon.

 

  • Tapping mode: The probe maintains a fixed frequency vibration in the Z-axis and contacts the sample when it vibrates to the valley bottom, with little damage to the sample and the resolution is almost the same as the contact mode.

 

Advantages of AFM:

(1) The sample does not need to be conductive;

(2) It can work in a variety of environments (such as vacuum, atmosphere, liquid, low temperature, etc.);

(3) High-resolution three-dimensional images of the object surface can be obtained;

(4) It can operate single cells and molecules, such as punching holes in the cell membrane and cutting chromosomes.

 

Application examples of AFM:

  • Characterize biological samples in liquid

(2) Observation of self-assembly process of biological samples

(3)Characterize nanomechanical properties

(4) Surface morphology of film materials

(5) Surface study of siderite under different conditions

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