Vibrating methods are used when the highest resolution is required or if very soft samples are being scanned. The probes used for vibrating mode are often less than 10 nm in diameter. The integrity of the probe during scanning at these high resolutions can be monitored with a "tip check" sample (Figure 4-10.)

FIGURE 4-10 2X2 micron AFM image of a tip checker sample.

Most of the extremely high resolution images measured with an AFM in ambient air are made with vibrating mode. Figure 4-11 illustrates images measured with vibrating mode:

FIGURE 4-11 Vibrating mode AFM images. Left: Silicon wafer. Center: Cancer cells. Right: Proteins.

Field modes are used to measure the electrostatic or magnetic fields above a surface. Typically, the vibrating mode discussed in Section 4.1.2 is used to measure the surface fields. That is, the probe is scanned above the surface such that the probe interacts with the electrostatic or magnetic fields that emanate from the surface.