The scan rate of an AFM limits the sizes of areas that can be analyzed to a few hundred microns at best. It would be highly desirable to create an AFM with multiple probes that could scan many areas simultaneously. Several efforts to create “multiple probe” atomic force microscopes demonstrated that it is possible. In the first approach, several AFM scanners were positioned above a silicon wafer and scanned independently. In the second approach, several probes on a silicon wafer were used to scan a sample simultaneously. The greatest challenge for creating multiple probe AFM instrumentation is to get all of the probes to be as sharp as is required for high resolution scanning.

As illustrated in Figure 2-40, there is considerable variability in the force constant of an AFM cantilever because of variations primarily in the thickness of the cantilevers. Thus, if the exact force is required for an AFM scan or F/D curve, the force constant for the cantilever used for the tests must be calculated. The primary method used for doing this is the Sader Method. In this method, the physical geometry of the cantilever is measured with an optical microscope and the quality factor, Q, is measured. These parameters are then used in an equation that calculates the force constant, (see Figure 2-43).