Principles of AFM

Fig. 5.2. Principle of AFM. The sample symbolized by the circles is scanned by means of a piezoelectric translator. The piezo crystal and the oscillator is only needed for tapping mode operation.

Fundamental Principles of AFM. The principles of AFM as applied to geochemical systems have been described in detail in many previous publications (e.g., 9-13). Briefly, AFM works by rastering a sample underneath a sharp tip that is attached to or part of a cantilever. A number of forces, including Van der Waals dispersion forces, the so-called atomic force (related to the Pauli exclusion principle), electrostatic forces, and others, cause the tip to deflect as different surface features pass beneath it. By monitoring this deflection, a 3-dimensional map of the sample surface can be constructed. AFM is commonly operated in so-called contact mode, wherein the tip is in direct contact with the sample surface and repulsive forces are dominant. Non-contact mode imaging, which is conducted in an attractive regime, commonly in aqueous solution, also is possible and has resulted in more reliable and interpretable atomic-scale imaging (e.g., 14). 

Biosensors Using Atomic Force Microscopes, Fig. 1 (a) Basic components and working principle of AFM. A sharp tip fixed at the end of a fiexible cantilever is raster scanned over the surface of a sample. As the tip interacts with the surface, the cantilever deflects, and its deflections are monitored by a laser and a photodiode and then used to reconstruct the topography of the sample, (b) A schematic diagram of AFM as a biosensor in detecting... 

SCHEME 30.1. Schematic drawing of the principle of AFM based SMFS. 

Working Principle of AFM-SECM What AFM Brings to SECM .750... 

WORKING PRINCIPLE OF AFM-SECM WHAT AFM BRINGS TO SECM ... 

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