Atomic force microscopy commercial tips

Atomic force microscopy (AFM) is another technique used to characterize nanocomposites.AFM can provide information about the mechanical properties of a surface at a length scale that is limited only by the dimensions of the AFM tip. AFM tips with 10 nm radius of curvature are readily available from commercial suppliers. When probing mechanical properties, the attractive and repulsive force interactions between the tip and sample are monitored. Schematic depicting the intercalation process between a polymer melt and an organic-modified layered silicate is shown on Figure 6.8. 

AFM (atomic force microscopy) was developed about five years after STM (see Atomic force microscopy). It relies upon the measurement of the force of interaction between a sharp tip and a sample. Being based upon the measurement of force rather than current, it is applicable in principle to any material. The technique has great versatility, and as in the case of STM, imaging may be carried out under ambient or fluid conditions. The tip is attached to a flexible cantilever, which is rastered across a sample surface. As the interaction force between the tip and the sample changes, the deflection of the cantilever varies. The cantilever deflection is readily measured (by optical deflection in most commercial systems) and is proportional to the interaction force leading to quantification, provided the spring constant of the lever is known. Either the cantilever or the sample is mounted on a piezoelectric crystal in order to exact fine control over the relative movements of the tip. 

The performance of SECM experiments in association with atomic force microscopy (AFM) is typically carried out using a commercial instrument. The concept involves converting the AFM tip into an electrode to operate as the SECM tip, and using the force signal to control its position above the sample surface [127-131]. The tip design (see discussion in Section 12.2.3) is critical and its fabrication technically challenging these points currently limit the take-up of this method. 

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