Atomic Force Microscope: Imaging Modes

Contact mode:

• As shown in Figure 19.04, the tip is dragged across the surface of the sample and the contours of the surface are measured either using the deflection of the cantilever directly or using the feedback signal required to keep the cantilever at a constant position.

Figure 19.04: Schematic of contact mode imaging.

• Low stiffness cantilevers are used to boost the deflection signal, as the measurement of a static signal is prone to noise and drift.

• Close to the surface of the sample, attractive forces can be quite strong, causing the tip to "snap-in" to the surface. Thus, contact mode AFM is done at a depth where the overall force is repulsive.