The material to be scanned is placed below the tip, as the tip moves across the surface it is attracted or repelled by different forces, the atomic deflection from rest is recorded and an imaging software is used to process the results. The results normally appears as a topographical image of the surface imaged2.
Different imaging techniques are used to picture the surface or for different surface analysis, they include the contact mode, non-contact mode and tapping mode. With assistance from specialized software, Atomic Force Microscope can be used to measure characteristics of material surface that other types of microscope cannot image.
This method is whereby the tip gets into contact with the surface being scanned, it is the most common mode used in atomic force scanning. The tip have a repulsive force coefficient of 9N. As the tip moves over the surface, the deflection of the cantilever generated is fed to a DC amplifier system, which verifies it and tries to much it with the desired. If the magnitude of deflections is different from the required one, the feedback amplifier system increases the voltage supply to the piezoelectric positioning system to raise or lower the material surface relative to the tip until the desired voltage is achieved3. The measure of voltage supplied to the piezoelectric positioning system gives the degree of roughness and surface features of the material. This is displayed laterally to the position of the sample.
The main problem with the contact mode is the application disproportionate force to the sample by the probe leading destruction of the sample surface; this can be minimized by reducing the amount of force applied by the probe. However, there are limits to the minimum force that the operator can apply during scanning in ambient conditions.
Ambient conditions possess some challenges to AFS since a thin layer of about 30 monolayers made up of