Chapter 4
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FIGURE 4-3 Left: SEM image of standard AFM Probe. Right: SEM image of an
AFM probe coated with a conductive diamond film.
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4.1 Topography Modes |
A force sensor in an AFM can only work if the probe interacts with the
force field associated with a surface. In ambient air, the potential energy
between the probe and surface is shown in Figure 4-4. There are three
basic regions of interaction between the probe and surface: |
- free space
- attractive region
- repulsive region
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FIGURE 4-4 Potential energy
diagram of a probe and sample.
The attractive potential is caused
by the capillary forces from surface
contamination. |
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Attractive forces near the surface are caused by a nanoscopic layer of contamination that is present on all surfaces in ambient air. The contamination is typically an aerosol composed of water vapor and hydrocarbons. The amount of contamination depends on the environment in which the microscope is being operated. Repulsive forces increase as the probe begins to "contact" the surface. The repulsive forces in the AFM tend to cause the cantilever to bend up. |
There are two primary methods for establishing the forces between a probe |
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